项目建设-双节短信

Content
PART 1 Introduction to Materials Science ＆Engineering 1
Unit 1 Materials Science and Engineering 1
Unit 2 Classification of Materials 9
Unit 3 Properties of Materials 17
Unit 4 Materials Science and Engineering: What does the Future Hold? 25
Part Ⅱ METALLIC MATERLALS AND ALLOYS
Unit 5 An Introduction to Metallic Materials
Unit 6 Metal Manufacturing Methods
Unit 7 Structure of Metallic Materials
Unit 8 Metal-Matrix Composites
Part Ⅲ Ceramics
Unit 9 Introduction to Ceramics
Unit 10 Ceramic Structures — Crystalline and Noncrystalline
Unit 11 Ceramic Processing Methods
Unit 12 Advanced ceramic materials – Functional Ceramics
PARTⅣ NANOMATERIALS
Unit 13 Introduction to Nanostructured Materials
Unit14 Preparation of Nanomaterials
Unit 15 Recent Scientific Advances
Unit 16 The Future of Nanostructure Science and Technology
Part Ⅴ POLYMERS
Unit17 A Brief Review in the Development of Synthetic Polymers
Unit18 Polymer synthesis: Polyethylene synthesis
Unit19 Polymer synthesis: Nylon synthesis
Unit 20 Processing and Properties Polymer Materials
PART VI POLYMERIC COMPOSITES
Unit21 Introduction to Polymeric Composite Materials
Unit22 Composition, Structure and Morphology of Polymeric Composites
33
33
47
57
68
81
81
88
97
105
112
112
117
126
130
136
136
146
154
165
172
172
178

Unit23 Manufacture of Polymer Composites 185
Unit24 Epoxy Resin Composites 191
Part 7 Biomaterial 196
Unit 25 Introduction to Biomaterials 196
Unit 26 Biocompatibility 205
Unit 27 Polymers as Biomaterials 213
Unit 28 Future of Biomaterials
PARTⅧ Materials and Environment
Unit29 Environmental Pollution & Control Related Materials
Unit30 Bio- degradable Polymer Materials 241
Unit 31 Environmental Friendly Inorganic Materials
Unit 32 A Perspective on the Future: Challenges and Opportunities
附录一 科技英语构词法
附录二 科技英语语法及翻译简介
附录三： 聚合物英缩写 、全名 、中文名对照表
附录四： 练习题参考答案









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PART 1 Introduction to Materials Science ＆
Engineering








Unit 1
Materials Science and Engineering

Historical Perspective

Materials are probably more deep-seated in our culture than most of us realize. deep-seated根深蒂固的,
Transportation, housing, clothing, communication, recreation, and food production 深层的
—virtually every segment of our everyday lives is influenced to one degree or

another by materials. Historically, the development and advancement of societies
have been intimately tied to the members’ ability to produce and manipulate materi-

als to fill their needs. In fact, early civilizations have been designated by the level of
their materials development (Stone Age, Bronze Age, Iron Age).
The earliest humans had access to only a very limited number of materials,
those that occur naturally: stone, wood, clay, skins, and so on. With time they
discovered techniques for producing materials that had properties superior to those
of the natural ones; these new materials included pottery and various metals. pottery
Furthermore, it was discovered that the properties of a material could be altered by

陶器
heat treatments and by the addition of other substances. At this point, materials
utilization was totally a selection process that involved deciding from a given, rather
limited set of materials the one best suited for an application by virtue of its
characteristics. It was not until relatively recent times that scientists came to
understand the relationships between the structural elements of materials and their
properties. This knowledge, acquired over approximately the past 100 years, has structural elements结构成
empowered them to fashion, to a large degree, the characteristics of materials. Thus, 分；property
①

tens of thousands of different materials have evolved with rather specialized charac- 

.性能

teristics that meet the needs of our modern and complex society; these include
metals, plastics, glasses, and fibers.

The development of many technologies that make our existence so comfortable
has been intimately associated with the accessibility of suitable materials. An
advancement in the understanding of a material type is often the forerunner to the
stepwise progression of a technology. For example, automobiles would not have
been possibl- e without the availability of inexpensive steel or some other stepwise 
comparable substitute. In our contemporary era, sophisticated electronic devices rely

逐步的
on components that are made from what are called semiconducting materials. sophisticated


Materials Science and Engineering

The discipline of materials science involves investigating the relationships that
exist between the structures and properties of materials. In contrast, materials
engineering is, on the basis of these structure–property correlations, designing or
engineering the structure of a material to produce a predetermined set of properties.


精制的，复杂的；
semiconducting materials
半导体材料

“Structure’’ is at this point a nebulous term that deserves some explanation. In

brief, the structure of a material usually relates to the arrangement of its internal
components. Subatomic structure involves electrons within the individual atoms and nebulous
interactions with their nuclei. On an atomic level, structure encompasses the 
organization of atoms or molecules relative to one another. The next larger structural

含糊的，有歧义
realm, which contains large groups of atoms that are normally agglomerated 的
together, is termed ‘‘microscopic,’’ meaning that which is subject to direct
subatomic
observation using some type of microscope. Finally, structural elements that may be 
viewed with the naked eye are termed ‘‘macroscopic.’’

亚原子的
The notion of ‘‘property’’ deserves elaboration. While in service use, all

materials are exposed to external stimuli that evoke some type of response. For
example, a specimen subjected to forces will experience deformation; or a polished microscopic
metal surface will reflect light. Property is a material trait in terms of the kind and


微
magnitude of response to a specific imposed stimulus. Generally, definitions of 观的
properties are made independent of material shape and size.

Virtually all important properties of solid materials may be grouped into six

different categories: mechanical, electrical, thermal, magnetic, optical, and

宏观的

deteriorative. For each there is a characteristic type of stimulus capable of provoking
different responses. Mechanical properties relate deformation to an applied load or deformation
force; examples include elastic modulus and strength. For electrical properties, such


变形
as electrical conductivity and dielectric constant, the stimulus is an electric field. The
thermal behavior of solids can be represented in terms of heat capacity and thermal
conductivity. Magnetic properties demonstrate the response of a material to the
application of a magnetic field. For optical properties, the stimulus is electro-
magnetic or light radiation; index of refraction and reflectivity are representative deteriorative
optical properties. Finally, deteriorative characteristics indicate the chemical
❖

破
reactivity of materials. 坏（老化的）
In addition to structure and properties, two other important components are elastic modulus 弹性模量
involved in the science and engineering of materials, viz. ‘‘processing’’ and
strength 


‘‘performance.’’ With regard to the relationships of these four components, the
强度；dielectric constant介
structure of a material will depend on how it is processed. Furthermore, a material’s
电常数；heat capacity 热容
performance will be a function of its properties. 量

refraction


折射率；
reflectivity


Fig. 1.1 Photograph showing the light transmittance of three aluminum oxide
specimens. From left to right: single crystal material (sapphire), which is transparent;
a polycrystalline and fully dense (nonporous) material, which is translucent; and a
polycrystalline material that contains approximately 5% porosity, which is opaque.
(Specimen preparation, P. A. Lessing; photography by J. Telford.)
We now present an example of these processing-structure-properties- perfor-
mance principles with Figure 1.1, a photograph showing three thin disk specimens
placed over some printed matter. It is obvious that the optical properties (i.e., the
❖

反射率

processing


加
工

light transmittance) of each of the three materials are different; the one on the left is
transparent (i.e., virtually all of the reflected light passes through it), whereas the
disks in the center and on the right are, respectively, translucent and opaque.
All of these specimens are of the same material, aluminum oxide, but the
leftmost one is what we call a single crystal—that is, it is highly perfect—which
gives rise to its transparency. The center one is composed of numerous and very
small single crystals that are all connected; the boundaries between these small transmittance
crystals scatter a portion of the light reflected from the printed page, which makes 

.
this material optically translucent. And finally, the specimen on the right is 透射性
composed not only of many small, interconnected crystals, but also of a large sapphire 

number of very small pores or void spaces. These pores also effectively scatter the 蓝宝石
reflected light and render this material opaque. transparent
②
Thus, the structures of these three specimens are different in terms of crystal


透明
boundaries and pores, which affect the optical transmittance properties. Furthermore, 的；polycrystalline
each material was produced using a different processing technique. And, of course, 
if optical transmittance is an important parameter relative to the ultimate in- service


多晶体；
application, the performance of each material will be different. translucent

Why Study Materials science and Engineering?

Why do we study materials? Many an applied scientist or engineer, whether
mechanical, civil, chemical, or electrical, will at one time or another be exposed to a
design problem involving materials. Examples might include a transmission gear,
the superstructure for a building, an oil refinery component, or an integrated circuit
chip. Of course, materials scientists and engineers are specialists who are totally
involved in the investigation and design of materials.
Many times, a materials problem is one of selecting the right material from the
many thousands that are available. There are several criteria on which the final
decision is normally based. First of all, the in-service conditions must be charac-
terized, for these will dictate the properties required of the material. On only rare
occasions does a material possess the maximum or ideal combination of properties.

半透明的；
opaque


不透明的


single crystal 单晶体

Thus, it may be necessary to trade off one characteristic for another. The classic
example involves strength and ductility; normally, a material having a high strength
will have only a limited ductility. In such cases a reasonable compromise between
two or more properties may be necessary.
A second selection consideration is any deterioration of material properties that
may occur during service operation. For example, significant reductions in mecha-
nical strength may result from exposure to elevated temperatures or corrosive envir-
onments.
Finally, probably the overriding consideration is that of economics: What will
the finished product cost? A material may be found that has the ideal set of proper-
ties but is prohibitively expensive. Here again, some compromise is inevitable.
The cost of a finished piece also includes any expense incurred during
fabrication to produce the desired shape. The more familiar an engineer or scientist
is with the various characteristics and structure–property relationships, as well as
processing techniques of materials, the more proficient and confident he or she will
be to make judicious materials choices based on these criteria.

Reference: William D. Callister, Materials science and engineering : an
introduction, Press:John Wiley & Sons, Inc.,2007;2-5
③




transmission gear 传动齿
轮





dictate 
❖
决定

trade off 权衡；折衷
ductility


延展性

overriding
❖

最主要的





judicious


明智的




Notes
1． At this point, materials utilization was totally a selection process that involved deciding from
a given, rather limited set of materials the one best suited for an application by virtue of its
characteristics
由此看来，材料的使用完全就是一个选择过程，且此过程又 是根据材料的性质从许
多的而不是非有限的材料中选择一种最适于某种用途的材料。
2． The center one is composed of numerous and very small single crystals that are all connected;
the boundaries between these small crystals scatter a portion of the light reflected from the
printed page, which makes this material optically translucent.
中心由无数相连的微小单晶体所组成；这些微小晶体 之间的界面散射了一部分从纸
面折射来的光，从而致使材料变为光学半透明。
3． The more familiar an engineer or scientist is with the various characteristics and structure–
property relationships, as well as processing techniques of materials, the more proficient and
confident he or she will be to make judicious materials choices based on these criteria.
工程师 或科学家对材料的各种性质、结构与功能之间的关系以及生产工艺越熟悉，
就能越熟练自信地根据这些标 准选择出最合适的材料。

Exercises
1. Choose the best answer for the following questions according to the text
(1)Why materials are so important in the modern times? ___
(a)Materials influence our everyday lives and accelerate the development and advancement of
societies.
(b) They are deep-seated in our culture.
(c) There are many kinds of materials.
(d) They are very expensive.
(2)What is the relationship between structure and properties ? ___
(a) Properties of materials depend largely on their structures.
(b) Structures of materials affect indirectly on their properties.
(c) Both of them have mutual effect.
(d) There are no direct relation between them.
2. Translate the following into Chinese
One of the reasons that synthetic polymers (including rubber) are so popular as engineering
materials lies with their chemical and biological inertness. On the down side, this characteristic is
really a liability when it comes to waste disposal. Polymers are not biodegradable, and, as such,
they constitute a significant land-fill component; major sources of waste are from packaging, junk
automobiles and domestic durables. Biodegradable polymers have been synthesized, but they are
relatively expensive to produce. On the other hand, since some polymers are combustible and do
not yield appreciable toxic or polluting emissions, they may be disposed of by incineration.
3. Put the following words into English
高分子化合物；多晶体；功能；化学反应活性；弹性体；参数；原子结构；参考标准；
加工工艺；多孔材料；延展性；弹性模量
4. Translate the following words into Chinese
aluminum oxide; characteristics of materials; specimens processing-structure-properties-
performance principles; mechanical strength；investigation and design of materials；transparent,
translucent and opaque.


Supplementary Reading

Metals and polycrystalline metals

Metals are an especially important class of materials. They are distinguished by several

special properties, namely their high thermal and electrical conductivity, their ductility and the
characteristic lustre of their surfaces. Their ductility, together with the high strength that can be
achieved by alloying, renders metals particularly attractive as engineering materials.
In nature, metals occur only seldom as they possess a high tendency for oxidation. If one
looks at the pure elements, more than two thirds of them are in a metallic state. Many elements
are soluble in metals in the solid state and thus allow to form a metallic alloy. For instance, steels
can be produced by alloying iron with carbon. The large number of metallic elements offers a
broad range of possible alloys. Of most technical importance are alloys based on iron (steels and
cast irons), aluminum, copper (bronzes and brasses), nickel, titanium, and magnesium.
In this section, we start by explaining the nature of the chemical bond of metals. We will see
that metals usually arrange themselves in a regular, crystalline order. Therefore, we will
afterwards discuss the structure of crystals and, finally, explain how a metallic material is
composed of such crystals.
Atoms in a metallic solid arrange themselves so that their electrons can spread over many
atoms. This spreading is most easy if the atoms are arranged in a dense and regular manner.
Therefore, metals form crystals which are distinguished by their well-ordered structure. To
understand the different types of crystal structures found in nature, it is useful to think rather
generally about the problem of arranging objects
If a metal is cooled down from a melt and solidifies, it starts to crystallise. Depending on the
cooling rate, many small nuclei of crystallisation （晶核）(form, small solidified regions with
crystalline structure. These nuclei then grow and coalesce.

(a) (b)
Fig. 1.1. Exemplary microstructures of metals (a) Micrograph (optical microscope) (b) Micro
-structure of a nickel-base alloy (scanning electron microscope （电子扫描显微镜）picture of an
intercrystalline fracture surface)
As the initial nuclei develop independently, they possess no long-range order （长程有序）
between them. Therefore, a metal does not usually consist of one single crystal with long-range
order, but rather of several crystalline regions called crystallites （微晶）or grains. They have a
diameter of the order of a few micrometres up to a fraction of a millimietre, but can also be much
larger in special cases. Grains can be made visible by polishing the surface of the metal and then
etching it because the acid attacks differently oriented grains differently ( figure 1.1(a)). The
structure of the grains of a metal is usually termed its microstructure.
The grain boundaries i. e., the interfaces between the grains, do not have a perfectly
crystalline order as differently oriented regions adjoin here. Therefore, they can be considered as

lattice imperfections. Frequently, they strongly influence the properties of a material because, for
example, they may be preferred diffusion paths for corroding media. This kind of weakening of
grain boundaries may then lead to failure of the material. This is called intercrystalline fracture
and is shown in figure 1.1(b).
Technical alloys frequently consist of different phases i. e., regions with differing chemical
composition or crystal structure. As we will see later, particles of a second phase that are enclosed
by a matrix of a first phase are especially important to influence mechanical properties（力学性
能）. One example for this is iron carbide (cementite, Fe
3
C) that increases the strength of steels
when precipitated （沉淀）as fine particles.
Depending in the crystal structure of the two phases, the interface between them may adopt
different structures: If the crystal structures and the crystal orientation of both phases are identical
and the lattice constants do not differ too much, the particles of the second phase will be coherent i.
e., the lattice planes of the matrix continue within the particle (see figure 1.2(a)). If the lattice
structure and orientation are identical, but the lattice constants differ strongly, the particles will be
semi-coherent because some lattice planes of the matrix continue inside the particle but others do
not (figure 1.2(b)). Generally, the crystal lattice is distorted near to the coherent or semi-coherent
particle. If the lattice structure of both phases or the lattice orientation differ, the particles are
incoherent; the lattice planes of particle and matrix have no relation at all (figure 1.3, Ommited).

(a) Coherent (b) Semi-coherent
Fig. 1.2 Coherent and semi- coherent particles. The symbol⊥in subfigure (b) denotes inserted
half-planes of the lattice. The edge where such a half-plane ends is called an edge dislocation.(a)
All crystal planes are continuous between matrix and particle（b）Some of the crystal planes are
continuous between matrix and particle.

Reference: Joachim Rösler, Harald Harders, Martin Bäical Behaviour
of Engineering Materials. Teubner Verlag Wiesbaden, 2007: 5-15

Unit 2
Classification of Materials



Solid materials have been conveniently grouped into three basic classifications:
metals and alloys ceramics, and polymers. This scheme is based primarily on ceramics 
chemical makeup and atomic structure, and most materials fall into one distinct

陶瓷；polymers
grouping or another, although there are some intermediates. In addition, there are 

聚合
three other groups of important engineering materials-composites, biomaterials and 物
advanced materials. A brief explanation of the material types and representative
characteristics is offered next.



Metals and Alloys
Metallic materials are normally combinations of metallic elements. They have
large numbers of nonlocalized electrons; that is, these electrons are not bound to
particular atoms. Many properties of metals are directly attributable to these nonlocalize electrons
electrons. Metals are extremely good conductors of electricity and heat and are not 离域电子，自由电子
transparent to visible light; a polished metal surface has a lustrous appearance.
Furthermore, metals are quite strong, yet deformable, which accounts for their lustrous 
extensive use in structural applications. Most of the elements in the Periodic Table

有光泽的
are metals. Examples of alloys are Cu-Zn (brass), Fe-C (steel), and Sn- Pb (solder).
Alloys are classified according to the majority element present. The main classes of brass 

黄铜
alloys are iron- based alloys for structures; copper-based alloys for piping, utensils,
thermal conduction, electrical conduction, etc.; and aluminum-based alloys for light- utensils
weight structures and metal-matrix composites. Alloys are almost always in the

器具
polycrystalline form.


Ceramics

Ceramics are compounds between metallic and nonmetallic elements; they are
most frequently oxides, nitrides, and carbides. The wide range of materials that falls

within this classification includes ceramics that are composed of clay minerals,
cement, and glass.

Fig. 2.1 Common objects that are made of ceramic materials: scissors, a china tea
cup, a building brick, a floor tile, and a glass vase. (Photography by S. Tanner.)



These materials are typically insulative to the passage of electricity and heat,
and are more resistant to high temperatures and harsh environments than metals and
polymers, such as Al
2
O
3
(for spark plugs and for substrates for microelectronics), insulative
SiO
2
(for electrical insulation in microelectronics), Fe
3
O
4
(ferrite for magnetic ❖
memories used in computers), silicates (clay, cement, glass, etc.), and SiC (an

绝缘的
abrasive). With regard to mechanical behavior, ceramics are hard but very brittle. spark plugs火花塞
Ceramics are typically partly crystalline and partly amorphous. They consist of ions ferrite 
(often atoms as well) and are characterized by ionic bonding and often covalent

铁酸盐
bonding.
abrasive ❖
Polymers

Polymers include the familiar plastic and rubber materials. Many of them are

organic compounds that are chemically based on carbon, hydrogen, and other 研磨剂
nonmetallic elements; furthermore, they have very large molecular structures. These amorphous
materials typically have low densities and may be extremely flexible. Polymers in 
the form of thermoplastics (nylon, polyethylene, polyvinyl chloride, rubber, etc.)

无定形的
consist of molecules that have covalent bonding within each molecule and van der
Waals’ forces between them. Polymers in the form of thermosets (e.g. epoxy,
phenolics etc.) consist of a network of covalent bonds. Polymers are amorphous,
except for a minority of thermoplastics. Due to the bonding, polymers are typically
electrical and thermal insulators. However, conducting polymers can be obtained by
doping, and conducting polymer- matrix composites can be obtained by the use of thermoplastics

conducting fillers.


热
塑性高分子；
Composite

A number of composite materials have been engineered that consist of more polyethylene
than one material type. Fiberglass is a familiar example, in which glass fibers are


聚乙
embedded within a polymeric material. A composite is designed to display a 烯；thermoset
combination of the best characteristics of each of the component materials. 

Fiberglass acquires strength from the glass and flexibility from the polymer. Many 热固性高分子；epoxy
of the recent material developments have involved composite materials. 

环氧
Composite materials are multiphase materials obtained by artificial combina 基树脂；phenolics
-tion of different materials to attain properties that the individual components cannot 

酚
attain. An example is a lightweight structural composite obtained by embedding 醛塑料
continuous carbon fibers in one or more orientations in a polymer matrix. The fibers
provide the strength and stiffness while the polymer serves as the binder. Another
example is concrete, a structural composite obtained by combining cement (the fiberglass玻璃纤维
matrix, i.e., the binder, obtained by a reaction known as hydration, between cement
and water), sand (fine aggregate), gravel (coarse aggregate), and, optionally, other
ingredients known as fibers and silica fume (a fine SiO
2
particul-
ate) are examples of admixtures. In general, composites are classified according to
their matrix materials. The main classes of composites are polymer-matrix, cement-
matrix, metal-matrix, carbon-matrix, and ceramic-matrix .
①
Polymer-matrix and cement-matrix composites are the most common due to the
low cost of fabrication. Polymer-matrix composites are used for lightweight struc
-tures (aircraft, sporting goods, wheelchairs, etc.) in addition to vibration damping, stiffness 
electronic enclosures, asphalt (composite with pitch, a polymer, as the matrix), and

硬度
solder -matrix composites in the form of concrete (with fine
and coarse aggregates), steel-reinforced concrete, mortar (with fine aggregate, but no
coarse aggregate), or cement paste (without any aggregate) are used for civil gravel ❖

structures, prefabricated housing, architectural precasts, masonry, landfill cover, 碎石
thermal insulation, and sound absorption. Carbon-matrix composites are important
②

for lightweight structures (like the Space Shuttle) and components (such as aircraft
brakes) that need to withstand high temperatures, but they are relatively expensive matrix
because of the high cost of fabrication. Carbon-matrix composites suffer from their


tendency to be oxidized (2C + O
2
→2CO), thereby becoming vapor. Ceramic- matrix 基体，母体
composites are superior to carbon-matrix composites in oxidation resistance, but
they are not as well developed. Metal- matrix composites with aluminum as the
matrix are used for lightweight structures and low- thermal-expansion electronic damping 
enclosures, but their applications are limited by the high cost of fabrication and by

阻尼；asphalt
galvanic corrosion.


沥青
mortar 

Biomaterials

Biomaterials are employed in components implanted into the human body for 研钵
replacement of diseased or damaged body parts. These materials must not produce
toxic substances and must be compatible with body tissues (i.e., must not cause masonry 
adverse biological reactions). All of the above materials—metals, ceramics,


polymers, composites, and semiconductors—may be used as biomaterials. For 砖石建筑
example, some of the biomaterials are utilized in artificial hip replacements. The
understanding and measurement of biocompatibility is unique to biomaterials
science. Unfortunately, we do not have precise definitions or accurate measurements
of biocompatibility. More often than not, it is defined in terms of performance or
success at a specific task. Thus, for a patient who is alive and doing well, with a
vascular prosthesis that is unoccluded, few would argue that this prosthesis is, in this
case, not However, this operational definition offers us little to
use in designing new or improved vascular prostheses. It is probable that enclosures
biocompatibility may have to be specifically defined for applications in soft tissue,


hard tissue, and the cardiovascular system (blood compatibility). In fact, 附件；galvanic corrosion
biocompatibility may have to be uniquely defined for each application. 电化学腐蚀
biomaterials
③
Advanced Materials

Materials that are utilized in high-technology (or high-tech) applications are

sometimes termed advanced materials. By high technology we mean a device or

生物材料

product that operates or functions using relatively intricate and sophisticated princi-
ples; examples include electronic equipment (VCRs, CD players, etc.), computers,
fiber optic systems, spacecraft, aircraft, and military rocketry. These advanced
mater- ials are typically either traditional materials whose properties have been
enhanced or newly developed, high-performance materials. Furthermore, they may biocompatibility
be of all material types (e.g., metals, ceramics, polymers), and are normally

relatively expensive. Semiconductors have electrical properties that are intermediate


生物相容性
between the electrical conductors (viz. metals and metal alloys) and insulators (viz.
ceramics and polymers). Furthermore, the electrical characteristics of these materials unoccluded不阻塞的
are extremely sensitive to the presence of minute concentrations of impurity atoms,
for which the concentrations may be controlled over very small spatial regions.
Semiconductors have made possible the advent of integrated circuitry that has totally
revolutionized the electronics and computer industries (not to mention our lives) cardiovascular
over the past three decades. Smart (or intelligent) materials are a group of new and
❖
state-of- the-art materials now being developed that will have a significant influence

心脏血管的
on many of our technologies. The adjective “smart” implies that these materials are

able to sense changes in their environments and then respond to these changes in
predetermined manners—traits that are also found in living organisms. In addition,
this “smart” concept is being extended to rather sophisticated systems that consist of

both smart and traditional materials.
Reference: William D. Callister, Materials science and engineering : an
introduction, Press:John Wiley & Sons, Inc.,2007:2-12
Deborah D.L. Chung,Applied Materials Science,
CRC Press

fiber optic光学纤维的



semiconductors


半导体；insul -ators

LLC,2001:1


绝缘体

smart( or intelligent)
materials智能材料











Notes
1. Another example is concrete, a structural composite obtained by combining cement (the matrix,
i.e., the binder, obtained by a reaction known as hydration, between cement and water), sand (fine
aggregate), gravel (coarse aggregate), and, optionally, other ingredients known as admixtures.
Short fibers and silica fume (a fine SiO
2
particulate) are examples of admixtures.
另一个例子就是混凝土，一种结构性复合材料，通 过水泥（基体，即粘合剂，通过水泥
和水之间的水合反应而制得）、沙子（细集料）、碎石 （粗集料） 以及其它可选用的材料
（统称混合物）结合而成的。其中混合物有诸如短纤维和气相SiO
2< br>（一种细SiO
2
颗粒）等。
r-matrix and cement- matrix composites are the most common due to the low cost of
fabrication. Polymer-matrix composites are used for lightweight structures (aircraft, sporting
goods, wheelchairs, etc.) in addition to vibration damping, electronic enclosures, asphalt
(composite with pitch, a polymer, as the matrix), and solder replacement.
因其制造成本低，以聚合物和水泥为基体的复合材料最为常见。聚合物-基体复合材料
用于轻构 筑物（如飞机，体育用品，轮椅等）以增加阻尼振动、电子设备、沥青（与一种作
为基体的聚合物—柏油 沥青进行复合）和焊接剂替代物。
, for a patient who is alive and doing well, with a vascular prosthesis that is unoccluded,
few would argue that this prosthesis is, in this case, not

因此，对于一 个使用人造血管而正常生活的病人来说，几乎没有人怀疑这种（辅助）
治疗是非“生物相容”的。

Exercises
1. Choose correct choice for each question according to the text
(1) __ _ is not the basic classifications of solid materials.
(a)metals (b) alloys ceramics (c) biomaterials (d)polymers
(2) is unique to biomaterials.
(a)biocompatibility (b)size (c) price (d) weight
(3) Advanced materials is thought of as _ .
(a) materials that are utilized in high- technology (or high-tech) applications
(b) high-performance materials (c) rare materials (d) sophisticated material
2. Put the following words into English
生物材料；高级材料；智能材料；热塑性高分子；热固性高分子；高性能材料；超导体
反应底物；生物相容性；电腐蚀；玻璃纤维
3. Put the following words into Chinese

atomic structure；metallic and nonmetallic elements；conductors of electricity and heat ；rubber；
metal-matrix composites；flexibility of the polymers；multiphase materials；living organisms;
components；polymeric reaction; oxidation;. polyethylene；electrons；polyvinyl chloride


Supplementary Reading

Inorganic and Inorganic–Organic Aerogels :Silica-based Aerogels

Aerogels （气凝胶）are highly porous solid materials with very low densities and high
specific surface areas. Their structure consists of a filigrane solid network with open, cylindrical,
branched mesopores. This results in interesting physical properties, such as extremely low thermal
conductivity and low sound velocity, combined with high optical transparency. Aerogels can be
obtained as monoliths, granulates, films, or powders. There are several review articles (Ayen and
Iacobucci 1988, Fricke and Emmerling 1992, Gesser and Goswami 1989, Heinrich et al. 1995,
and Schubert 1998) and symposium proceedings on aerogels (Fricke 1986, 1992, Pekala
and Hrubesch 1995,Phalippou and Vacher 1998).
Silica-based Aerogels

The term ‘‘SiO
2
gel’’ (correspondingly for other gels) is used to characterize the type of
inorganic skeleton.‘‘SiO
2
gels’’ and the corresponding aerogels often have the composition
SiO
x
(OH)
y
or, if they are prepared from alkoxides（醇盐(烃氧化物类)）, SiO
x
(OH)y(OR)
z
, where
the values of y and z can be rather high. Most laboratory preparations of silica aerogels use
tetraalkoxysilanes (Si(OR)
4
) as the silica source. The less expensive aqueous（ 水成的）sodium

silicate solutions (water glass) are used for larger-scale technical applications. The sodium silicate
solution is ion-exchanged and the resulting silicic acid solution gelled by lowering the pH.
The kind of inorganic network formed by sol–gel （溶胶—凝胶）processing depends to a
large extent on the relative rates of the hydrolysis（水解） and condensation(缩聚) reactions.
Hydrolysis is the rate-determining step （速率决定步骤）under basic conditions, where reaction at
central silicon atoms of an oligomeric unit is favored. The network of the resulting colloidal gels
consists of big particles and large pores. The clusters mainly grow by the condensation of
monomers, because condensation of clusters is relatively unfavorable. Acidic conditions (pH=2–5)
favor hydrolysis, and condensation is the rate-determining step. A great number of monomers or
small oligomers with reactive Si–OH groups is simultaneously formed. Reactions at terminal
silicon atoms are favored. This results in polymer like networks with small pores.
Complete removal of the pore liquid from the smaller pores in polymeric gels is more
difficult, resulting in a larger shrinkage during drying. For this reason, silica aerogels are usually
prepared by base catalyzed reaction of Si(OR)
4
. A modification of this procedure is to
prehydrolyze（预水解） Si(OR)
4
with a small amount of water under acidic conditions. In a
second step, a defined amount of aqueous acid or base is added. Base catalysis in the second step
results in a stiffening of the network that stabilizes the gels. This two-step procedure allows a
more deliberate control of the microstructure of the SiO
2
gels.
The macroscopic properties of SiO
2
aerogels differ widely, due to structural differences.
Silica aerogels with bulk densities as low as 0.003 g cm
-3
(99.8% porosity) have been prepared.
Typical values are in the range 0.1–0.2 g cm
-3
(85–90% porosity). Skeletal densities are in the
range 1.7–2.1 g cm
-3
, mean pore diameters are in the range 20–150 nm, and specific surface areas
are in the range 100–1600m
2
g
-1
. Silica aerogels are always amorphous.
The spectrum of properties can be widened by modification of silica aerogels with organic
entities. For example, the hydrophobicity（疏水性） and the elastic properties of SiO
2
aerogels are
improved by incorporation of organic groups, and new applications can be envisioned by the
integration of functional organic moieties. Any modification should retain the gel network and the
pore structure, because the interesting physical properties of aerogels result from these.
Possibilities of postsynthesis doping or modification of aerogels with organic compounds are
limited. Therefore, the organic groups have to be incorporated during sol–gel processing.
Embedding molecules or polymers in gels is achieved by dissolving them in the precursor solution.
The gel matrix is formed around them and traps them. The doped wet gels can be converted to
aerogels. However, the probability is very high that the organic groups are leached out during the
drying process.
A more general route for the organic modification is to use hydrolyzable and condensable
precursors for sol–gel processing in which the organic group is covalently attached to the silicon
atom and will therefore be bonded to the inorganic network. Silica aerogels modified by
nonfunctional or functional organic groups are prepared by sol–gel processing of RSi(OR)
3

Si(OR)
4
mixtures followed by supercritical drying of the wet gels. The process can be controlled
in such a way that the organic groups cover the inner surface of the gel network without
influencing its basic structure.
Future Perspectives

The unique optical, thermal, acoustic（声学）, and mechanical properties of aerogels originate
from the combination of a solid matrix (the chemical composition of which can be modified) and

nanometer-sized pores filled with air. There is a direct connection between the chemistry of the
sol–gel process and the structure of the gels on one hand, and between the structure and the
properties of the aerogels on the other. The most important area for the application of aerogels is
thermal insulation, while important acoustic insulation applications are emerging. There is no
doubt about the physical and ecological advantages (nontoxic, nonflammable, easily disposed) of
SiO
2
aerogels compared with most other materials on the market.
Apart from special applications in which material costs only play a minor role, the rather high
price of supercritically dried aerogels has prevented a broader range of applications. The new
ambient pressure drying techniques will probably make the technical preparation much cheaper
and will thus make aerogels more competitive. They will also allow the preparation of aerogels
with standard laboratory equipment.

Reference: A. e Encyclopedia of Composite
:Elsevier Ltd, 2007:435-438,441







Unit 3
Properties of Materials






Materials, Processes and Choice

Engineers make things. They make them out of materials. The materials have to
support loads, to insulate or conduct heat and electricity, to accept or reject magnetic
flux, to transmit or reflect light, to survive in often-hostile surroundings, and to do flux 

变迁
all this without damage to the environment or costing too much.
And there is the partner in all this. To make something out of a material you
also need a process. Not just any process—the one you choose has to be compatible compatible
with the material you plan to use. Sometimes it is the process that is the dominant


相兼容
partner and a material-mate must be found that is compatible with it. It is a marriage. 的

Compatibility is not easily found—many marriages fail and material failure can be

catastrophic, with issues of liability and compensation. This sounds like food for
lawyers, and sometimes it is: some specialists make their living as expert witnesses
in court cases involving failed materials. But our aim here is not contention; rather, it
is to give you a vision of the materials universe (since, even on the remotest planets



you will find the same elements) and of the universe of processes, and to provide
methods and tools for choosing them to ensure a happy, durable union.
①

With the ever-increasing drive for performance, economy and efficiency, and
the imperative to avoid damage to the environment, making the right choice be-
comes very important. Innovative design means the imaginative exploitation of the
properties offered by materials.
Material Properties

So what are these properties? Some, like density(mass per unit volume) and
price (the cost per unit volume or weight) are familiar enough, but others are not,
and getting them straight is essential. Think first of those that have to do with
carrying load safely—the mechanical properties.

Mechanical properties

Steel ruler is easy to bend elastically—‘elastic’ means that it springs back when
released. Its elastic stiffness (here, resistance to bending) is set partly by its
shape—thin strips are easy to bend—and partly by a property of the steel itself: its
elastic modulus, E. Materials with high E, like steel, are intrinsically stiff; those with
low E, like polyethylene, are not. The steel ruler bends elastically, but if it is a good
one, it is hard to give it a permanent bend. Permanent deformation has to do with
strength, not stiffness. The ease with which a ruler can be permanently bent depends,
again, on its shape and on a different property of the steel—its yield strength, σ
y
.
Materials with large σ
y
, like titanium alloys, are hard to deform permanently even
though their stiffness, coming from E, may not be high; those with low σ
y
, like lead,
can be deformed with ease. When metals deform, they generally get stronger (this is
called ‘work hardening’), but there is an ultimate limit, called the tensile strength,
σ
ts
, beyond which the material fails .







density 

密度



mechanical properties力学
性能

elastic stiffness抗张强度

elastic modulus 弹性模量




yield strength 屈服强度
titanium


So far so good. One more. If the ruler were made not of steel but of glass or of

钛

PMMA (Plexiglas, Perspex), as transparent rulers are, it is not possible to bend it
permanently at all. The ruler will fracture suddenly, without warning, before it
acquires a permanent bend. We think of materials that break in this way as brittle, work hardening加工硬化
and materials that do not as tough. There is no permanent deformation here, so σ
y
is tensile strength抗张强度
not the right property. The resistance of materials to cracking and fracture is
measured instead by the fracture toughness, K
1c
. Steels are tough—well, most are plexiglas
(steels can be made brittle)—they have a high K
1c
. Glass epitomizes brittleness; it 
has a very low K
1c
.

胶质玻璃
We started with the material property density, mass per unit volume, symbol ρ. perspex 
Density, in a ruler, is irrelevant. But for almost anything that moves, weight carries a

有机玻璃

fuel penalty, modest for automobiles, greater for trucks and trains, greater still for
aircraft, and enormous in space vehicles. Minimizing weight has much to do with
clever design—we will get to that later—but equally to choice of material.
Aluminum has a low density, lead a high one. If our little aircraft were made of lead,
it would never get off the ground at all .These are not the only mechanical
properties, but they are the most important ones.





penalty 
Thermal properties

The properties of a material change with temperature, usually for the worse. Its

补偿
strength falls, it starts to ‘creep’ (to sag slowly over time), it may oxidize, degrade or
decompose. This means that there is a limiting temperature called the maximum
service temperature, T
max
, above which its use is impractical. Stainless steel has a
high T
max
—it can be used up to 800°C; most polymers have a low T
max
and are
seldom used above 150°C.
Most materials expand when they are heated, but by differing amounts
depending on their thermal expansion coefficient, a. The expansion is small, but its
consequences can be large. If, for instance, a rod is constrained and then heated,
expansion forces the rod against the constraints, causing it to buckle. Railroad track
buckles in this way if provision is not made to cope with it.
②







creep 
❖
蠕
变
sag 
❖
凹陷

Some materials—metals, for instance—feel cold; others—like woods—feel wa- maximum service tempera-
rm. This feel has to do with two thermal properties of the material: thermal conducti- ture最大使用温度
vity and heat capacity. The first, thermal conductivity, λ, measures the rate at which
heat flows through the material when one side is hot and the other cold. Materials
with high λ are what you want if you wish to conduct heat from one place to another,
stainless 

不锈的


as in cooking pans, radiators and heat exchangers. But low λ is useful too—low λ
materials insulate homes, reduce the energy consumption of refrigerators and freeze-
rs, and enable space vehicles to re-enter the earth’s atmosphere.
These applications have to do with long-time, steady, heat flow. When time is
limited, that other property—heat capacity, Cp—matters. It measures the amount of
heat that it takes to make the temperature of material rise by a given amount. High
heat capacity materials—copper, for instance—require a lot heat to change their
temperature; low heat capacity materials, like polymer foams, take much less.
Steady heat flow has, as we have said, to do with thermal conductivity. There is a
subtler property that describes what happens when heat is first applied. Think of
lighting the gas under a cold slab of material with a bole of ice-cream on top (here,
lime ice-cream). An instant after ignition, the bottom surface is hot but the rest is
cold. After a while, the middle gets hot, then later still, the top begins to warm up
and the ice-cream first starts to melt. How long does this take ? For a given
thickness of slab, the time is inversely proportional to the thermal diffusivity, a, of
the material of the slab. It differs from the conductivity because materials differ in
their heat capacity—in fact, it is proportional to λCp.
Electrical, magnetic and optical properties

Without electrical conduction we would lack the easy access to light, heat,
power, control and communication that—today—we take for granted. Metals
conduct well—copper and aluminum are the best of those that are affordable. But
conduction is not always a good thing. Fuse boxes, switch casings, the suspensions
for transmission lines all require insulators, and in addition those that can carry some
load, tolerate some heat and survive a spark if there were one. Here the property we



thermal conductivity热导
率
heat capacity热容量












lime 

石灰
ignition 

灼热

want is resistivity, ρ
e
, the inverse of electrical conductivity κ
e
. Most plastics and
glass have high resistivity—they are used a insulators—though, by special treatment,
they can be made to conduct a little.
Electricity and magnetism are closely linked. Electric currents induce magnetic
fields; a moving magnet induces, in any nearby conductor, an electric current. The
response of most materials to magnetic fields is too small to be of practical value.
But a few—called ferromagnets and ferrimagnets—have the capacity to trap
magnetic field permanently. These are called ‘hard’ magnetic materials because once
magnetized, they are hard to demagnetize. They are used as permanent magnets in
headphones, motors and dynamos. Here the key property is the remanence, a
measure of the intensity of the retained magnetism. A few others—‘soft’ magnet
materials—are easy to magnetize and demagnetize. They are the materials of
transformer cores and the deflection coils of a TV tube. They have the capacity to
conduct a magnetic field, but not retain it permanently . For these a key property is
the saturation magnetization, which measures how large a field the material can
conduct.
Materials respond to light as well as to electricity and magnetism hardly
surprising, since light itself is an electromagnetic wave. Materials that are opaque
reflect light; those that are transparent refract it, and some have the ability to absorb
some wavelengths (colors) while allowing others to pass freely.
③






fuse boxes保险丝盒

transmission lines输电线
路







ferromagnets


铁磁体


dynamos


动力测验器；remanence
 
顽磁

transformer cores变压器
铁心；deflection coils偏转
线圈

eletronmagnetic wave电磁
波
Chemical properties

Products often have to function in hostile environments, exposed to corrosive
fluids, to hot gases or to radiation. Damp air is corrosive, so is water; the sweat of
your hand is particularly corrosive, and of course there are far more aggressive
environments than these. If the product is to survive for its design life it must be
made of materials—or at least coated with materials—that can tolerate the
suroundings in which they operate.
Reference: Michael Ashby, Hugh Shercliff and David Cebon, Materials Engineering,
Science,Processing and Design,Press: Elsevier Ltd.,2007:2-9

refract 
❖
折射










Notes

1. But our aim here is not contention; rather, it is to give you a vision of the materials universe
(since, even on the remotest planets you will find the same elements) and of the universe of
processes, and to provide methods and tools for choosing them to ensure a happy, durable
union.
但我们在此的目的不是争辩，而是让大家对材料世界（因为即 使是在遥远的外星球
你也能发现相同的元素）和加工领域有一个了解，提供选择材料的方法和工具，以确 保
上述方面能长期友好地结合起来。
2. Railroad track buckles in this way if provision is not made to cope with it.
如果铁轨加工时未采取相应处理，也会发生这样的弯曲。
3. Materials that are opaque reflect light; those that are transparent refract it, and some have the
ability to absorb some wavelengths (colors) while allowing others to pass freely.
不透明的材料能使 光发生反射；半透明的材料能使光发生折射，其中一些材料还能
吸收某些波长（颜色）的光但也能让其他 一些光自由通过。

Exercises
1. Translate the following paragraph into Chinese

Products often have to function in hostile environments, exposed to corrosive fluids, to hot
gases or to radiation. Damp air is corrosive, so is water; the sweat of your hand is particularly
corrosive, and of course there are far more aggressive environments than these. If the product is to
survive for its design life it must be made of materials—or at least coated with materials—that can
tolerate the suroundings in which they operate.

2. Choose the most appropriate answer for the following questions according to the text
(1) When we have to choose a process to make something out of material for special purpose, we
should firstly consider____?
(a) Dose the process be compatible with the material you plan to use (b) The special purpose
(c) The application of the material (d) The cost of the whole technology
(2) If we want to make a superconductor, we should pay close attention to its ____ properties；but
when making a elastomer, we need to watch out for its ____ properties.
(a) mechanical (b) thermal (c) chemical (d) magnetic (e) optical
(e) electrical
3. Put the following words into English
热容量；弹性模量；密度；加工硬化；应力；应变；电磁波；折射； 化学性质；蠕变；
腐蚀；电阻率；热导率

4. Put the following words into Chinese
transmit or reflect light；brittleness；electrical conductivity；electric current；yield strength
thermal expansion coefficient；maximum service temperature； buckle; diffusivity of heat；
symmetry；magnetism；tensile strength；elastic stiffness; creep; optical properties.



Supplementary Reading

Structure–Property Relationships

The physical and chemical properties of crystals and textured materials often depend on
direction. An understanding of anisotropy (各向异性) requires a mathematical description
together with atomistic arguments to quantify the property coefficients in various directions.
Tensors and matrices are the mathematics of choice and the atomistic arguments are partly based
on symmetry and partly on the basic physics and chemistry of materials. These are subjects of this
book: tensors, matrices, symmetry, and structure–property relationships.
Outline
We begin with transformations and tensors and then apply the ideas to the various symmetry
elements found in crystals and textured polycrystalline materials. This brings in the 32 crystal
classes and the 7 Curie （居里） groups. After working out the tensor and matrix operations used
to describe symmetry elements, we then apply Neumann’s Law（诺伊曼定律） and the Curie
Principle of Symmetry Superposition to various classes of physical properties. The first group of
properties is the standard topics of classical crystal physics: pyroelectricity（焦热电）, permittivity
（介电常数）, piezoelectricity(压电), elasticity, mechanical specific heat（比热）, and thermal
expansion. These are the linear relationships between , electrical, and thermal variables. These

standard properties are all polar tensors ranging in rank from zero to four. Axial tensor properties
appear when magnetic phenomena are introduced. Magnetic susceptibility, the relationship
between magnetization and magnetic field, is a polar second rank tensor, but the linear
relationships between magnetization and thermal, electrical, and mechanical variables are all axial
tensors. Magnetization can be added to the Heckmann Diagram （赫克曼图标）converting it into
a tetrahedron （四面体）of linear relationships. Pyromagnetism（热磁性）, magnetoelectricity, and
piezomagnetism （压电磁性）are the linear relationships between magnetization and temperature
change, electric field, and mechanical stress.
Examples of tensors of rank zero through four are given in Table 1.1 In this book we will also
treat many of the nonlinear relationships such as magnetostriction（磁力控制）, electrostriction
（电缩作用）, and higher order elastic constants.
The third group of properties is transport properties that relate flow to a gradient. Three
common types of transport properties relate to the movement of charge, heat, and matter.
Electrical conductivity, thermal conductivity, and diffusion are all polar second rank tensor
properties. In addition, there are cross-coupled phenomena（交叉耦合现象）such as
thermoelectricity, thermal diffusion, and electrolysis in which two types of gradients are involved.
All these properties are also influenced by magnetic fields and mechanical stress leading to
additional cross-coupled effects such as piezoresistivity and the Hall Effect（磁场电势差）.
A fourth family of directional properties involves hysteresis and the movement of domain
walls. These materials can be classified as primary and secondary ferroics（电性体），according to
the types of fields and forces required to move the walls. The primary ferroics include such
well-known phenomena as ferromagnetism, ferroelectricity, and ferroelasticity. Less well known
are the secondary ferroic effects in materials like quartz which show both ferrobielasiticity and the
ferroelastoelectric effect.
Crystal optics has long been an important part of crystal physics with roots in classical optical
mineralogy. In modern times this has become an important component of the information age
through the applications of nonlinear optics, magneto-optics and electro-optics. Linear and
nonlinear ultrasonic phenomena are an important part of physical acoustics which are analogous to
the optical effects.
Crystalline and noncrystalline media with handedness exhibit several types of gyrotropy （回
旋磁性）in which the plane of polarization rotates as the wave passes through the medium. This
leads to an interesting group of tensor properties known as optical activity, acoustical activity, and
the Faraday Effect （法拉第效应）.

Table 1.1 Polar and axial tensor properties of rank 0, 1, 2, 3, and 4. The rank of a tensor is
nothing mysterious. It is simply the number of directions involved in the measurement of the
property .A few examples are included
Rank
Zero
First
Second
Third
Fourth
Polar
Specific heat
Pyroelectricity
Thermal expansion
Piezoelectricity
Elastic compliance
Axial
Rotatory power
Pyromagnetism
Magnetoelectricity
Piezomagnetism
Piezogyrotropy
When faced with the task of identifying useful materials, the materials scientist uses atomic
radii, chemical bond strengths, anisotropic atomic groupings, electronic band structure, and

symmetry arguments as criteria in the material selection process.
Crystal physics is mainly concerned with the relationships between symmetry and the
directional properties of crystals. Symmetry and its relationships to physical properties is reviewed
in the next section. In general, symmetry arguments are useful in determining which property
coefficients are absent and which are equal, but not in estimating the relative sizes of the coeffi-
cients. Magnitudes depend more on the atomistic arguments based on crystal chemistry and solid-
state physics. Using examples drawn from engineering technology, I have tried to point out the
crystallochemical parameters most important to the understanding of a molecular mechanism（分
子机理）, and to the choice of new materials.
For most scientists and engineers, an important goal is to develop fundamental understanding
while at the same time remaining alert for possible applications. In solving solid- state problems it
is helpful to ask, what atoms are involved and what are their electron configurations （构型）?
What types of chemical bonds are formed? What is the symmetry of the crystal? How are the
atoms arranged in the crystal structure? Are there chains or layers that give rise to anisotropy? Do
these arrangements promote certain mechanisms for electronic or atomic motions or distortions?
How do these mechanisms give rise to the observed properties? Which properties are important in
engineering applications?

Reference: Robert E. Newnham, Properties of Materials ,Press: OxfordUniversity, US,2005:1-4

Unit 4
Materials Science and Engineering :
What does the Future Hold?

Very few people, if any, probably would have predicted 50 years ago what kind




of materials would dominate our technology today. Who could foresee the computer
revolution and thus the preponderance of silicon in the electronics industry? How preponderance
many scientists or engineers prognosticated the laser and its impact on communica- 
tion, data- processing, data storage, and thus on optical materials? Was there anybody

优势
who foretold, 50 years ago, the impact of super alloys, of composites, or of graphite prognosticate
fibers as important materials? Were ceramics not essentially perceived as clay and 
sand; that is, could anybody anticipate high-tech ceramics, Including high Tc- super

❖
预知
conductors, heat- resistant tiles (for space shuttles), silicon carbide engine parts, etc.? laser 

激
And finally, how many people could visualize 50 years ago the impact of plastics as 光
one of the prime materials of the present day, or an accentuation on recycling and alloy 

合金
environmental protection? graphite 
On the other hand, nearly “everybody” predicted only 15 years ago that compo-

石墨
sites and ceramics for high-temperature engines would be the materials which would Tc温度系数

enjoy healthy growth rates in the years to come. This, however, has not happened. accentuation
One of the major funding agencies in the United States (ARPA) has recently stated 
that the past 20 years have not brought the expected progress in structural ceramics,


强调
brittle matrix composites, or intermetallics. It is said that these “exotic” materials
may probably never be used in critical parts such as turbine blades because they are
too brittle, and a balance of properties may probably never be achieved. A 50% cut
in support for the ensuing projects has therefore occurred. Instead, a resurgence of ARPA远景研究规化局
substantial interest in metals research may boost, for example, nickel-based
super-alloys (e.g., Ni–Al) which are often coated with μ
m
-thick heat barriers. These intermetallic
coatings, consisting, for example, of zirconia or Ni–Cr–Al–Y are anticipated to 
prevent the respective alloys in turbine blades from melting or creeping. In other

金属互化物(金属间化
words, a change in research support from “exotic” materials to new alloys is
物)

presently thought to be more in the national interest. In essence, a shift from turbine blades涡轮叶片
structural materials (such as ceramics, composites, etc.) to functional materials resurgence
(such as smart materials, electromagnetic materials, and optical materials) will 

probably take place in the next couple of years. Specifically, future funding is 复活
anticipated for the development of compact lasers, solid-state lighting through zirconia
inorganic and organic light-emitting diodes, holographic data storage, thermoelectric 

materials (used for cooling of high Tc superconductors, microprocessors, IR 氧化锆
detectors, etc.) and for smart materials (which involve a series of sensors that control
actuators). Further, a shift from empirical materials selection towards one based on
model calculations and on a fundamental understanding of the physics and chemistry
of materials science will probably take place. Finally, the exploration of nano- smart materials智能材料；
structures and nanotechnology will probably play a major role in future research electromagnetic materials
funding. 电磁材料；optical material
Materials Science has expanded from the traditional metallurgy and ceramics 光学材料；light-emitting
into new areas such as electronic polymers, complex fluids, intelligent materials, diodes发光二极管；holo-
organic composites, structural composites, biomedical materials (for implants and graphic data storage全
other medical applications), biomimetics, artificial tissues, biocompatible materials, 信息数据储存；micropro-
“auxetic” materials (which grow fatter when stretched), elastomers, dielectric
cessors☺
ceramics (which yield thinner dielectric layers for more compact electronics), ferro-
☺

微处理
electric films (for nonvolatile memories), more efficient photovoltaic converters, 器
ceramic superconductors, improved battery technologies, self-assembling materials, nanotechnology
fuel cell materials, optoelectronics, artificial diamonds, improved sensors (based on

metal oxides, or conducting polymers), grated light valves, ceramic coatings in air

纳米技术
(by plasma deposition), electrostrictive polymers, chemical-mechanical polishing, metallurgy
alkali metal thermoelectric converters, luminescent silicon, planar optical displays 

without phosphors, MEMS, and supermolecular materials. Some materials scientists 冶金学
are interested in green approaches, by entering the field of environ- mental-
biological science, by developing environmentally friendly processing techniques biomimetics
and by inventing more recyclable materials.


仿

Another emerging field is called Nanomaterials by severe plastic deformation 生学；Auxetic
(SPD) which involves the application of very high strains and flow stresses to work 
pieces. As the name implies, the respective new process yields microstructural

增大的，促诱的；
features and properties in materials (notably metals and alloys) that differ from those nonvolatile永久的，非挥
known for conventional cold-worked materials. Specifically, pore-free grain 发的；photovoltaic
refinements down to nanometer dimensions, and dislocation accumulations up to the converters光电池的转化
limiting density of 10
16
m
-2
are observed. SPD yields an increase in tensile ductility 器；self-assembling mater-
without a substantial loss in strength and fatigue behavior. Furthermore, unusual ials自组装材料；fuel cell
phase transformations leading to highly metastable states have been reported and are materials燃料电池；opto-
associated with a formation of supersaturated solid solutions, disordering, amorphi- electronics
zation, and a high thermal stability. Moreover, superplastic elongations in alloys that

are generally not superplastic can be achieved. This affords a superplastic flow at

光学电子学；grat- ed
strain rates significantly faster than in conventional alloys, enabling the rapid light valves格栅光阀；
fabrication of complex parts. Finally, the magnetic properties of severely plastic alkali metal碱金属
deformed materials are different from their conventional counterparts. In particular, luminescent
one observes an enhanced remanence in hard magnetic materials, a decrease of


发光
coercivity, (i.e. energy loss) in soft magnetic materials, and an induced magnetic 的；phosphor 
anisotropy.
①

磷光剂；MEMS微电
In short, the field of materials science is extending into new territory and this 子机械系统
trend is expected to continue.
Still, “Predictions are quite difficult to make, particularly if they pertain to the

future.” As an example, a U.S. congressman suggested at the end of the 19th century
tensile ductility拉伸延性
that the patent office should be abolished, “since all major inventions have been metastable states亚稳状
made already.” Moreover, it has been shown more than once that extrapolations of 态
the present knowledge and accomplishments into the years which lay ahead were supersaturated超饱和的
flatly wrong. Thus, utmost care needs to be exercised when projections are made. disorder 
One particular graph (Omitted) that demonstrates essentially correct predic-

无序
tions is worthy of some considerations. The figure depicts the number of transistors amorphization
on a semiconductor chip in yearly intervals and reveals that initially the transistor



density doubles about every 12 months. This plot, which was empirically deduced 无定形化
from earlier production figures (by an extrapolation of only three earlier data points),
was dubbed Moore’s law (after Gordon E. Moore at Fairchild Semiconductor) and
depicts a log-linear relationship between device complexity and time. This type of remanence
prediction into the future is often referred to as a controlling variable, or a self- 

顽
fulfilling prophecy since each computer chip manufacturer knows what the compe- 磁
②
；coercivity
titor will present in a given amount of time and acts accordingly. In other words,  ❖
Moore’s law involves human ingenuity for progress rather than physics. Higher

矫顽性(矫顽磁力)
transistor densities means higher processing speeds, lower power consumption, anisotropy
better reliability, and reduced cost. Beginning in the mid-seventies, the slope became


各向异性
less steep but still behaved in a log-linear fashion, and the rate of density doubling
slowed down to every 18 months. (At the same time interval the magnetic storage
density on hard disk drives doubled every 3 years.)
On the other hand, for each doubling of performance, new and more sophis- extrapolation
ticated production facilities which may have price tags of about twice the previous

factory, have to be built. Specifically, it is predicted that by 2005 a single chip

外推
fabrication facility will cost 10 billion dollars or 80 % of Intel’s net worth. Thus,
eventually there may be no economic incentive anymore to make transistors smaller
unless computer chip companies team together (such as IBM and Toshiba, or

Motorola and Siemens) and share a given facility.

While the substantial improvement of physical properties during the past 40

years is certainly impressive, it probably would be wrong to assume that a similar

sharp rise would continue in the next decade or two. Indeed, certain limitations exist

when, for example, atomistic dimensions are reached. This may stifle further
log-linear relationship对
progress as long as the same conventional methods are applied. In other words, new,
数线性关系；controlling
innovative concepts are needed instead and probably will be found.

Reference: Rolf E. tanding Materials Science, New York: Springer-Verlag,2004:407-411
variable控制变量

stifle 

抑制





Notes

r emerging field is called nanomaterials by severe plastic deformation (SPD) which
involves the application of very high strains and flow stresses to work pieces.
另一个新 兴领域是经强烈塑性变形法而成的纳米材料，强烈塑性变形法需要采用非常高
的应变和流体应力。
type of prediction into the future is often referred to as a controlling variable, or a self-
fulfilling prophecy since each computer chip manufacturer knows what the competitor will present
in a given amount of time and acts accordingly.
这种预言常作为一种控制变量或可自我实现的，因为每个电脑芯片制造者都 知道竞争者
在一定时间内将有什么新发现，由此采取相应的措施。

Exercises
1
．
Choose the Preferable Paragraph Heading for each Paragraph of the following
（1） The economics of engineering are very important in product design and manufacturing.
To minimize product cost, materials engineers must take into account component design, what
materials are used, and manufacturing processes. Other significant economic factors include fringe
benefits, labor, insurance, profit, etc. ____
（2）Environmental and societal impacts of production are becoming significant engineering
issues. In this regard, the material cradle- to-grave life cycle is an important consideration; this
cycle consists of extraction, synthesisprocessing, product designmanufacture, application, and
disposal stages. Materials, energy, and environmental interactionsexchanges are important factors
in the efficient operation of the materials cycle. The earth is a closed system in that its materials
resources are finite; to some degree, the same may be said of energy resources. Environmental
issues involve ecological damage, pollution, and waste disposal. Recycling of used products and
the utilization of green design obviate some of these environmental problems.____
（3） Recyclability and disposability issues were addressed in the context of materials
science and engineering. Ideally, a material should be at best recyclable, and at least biodegradable
or disposable. The recyclability and disposability of metal alloys, glasses, polymers, and
composites were also discussed.____
(a) “Environmental and Societal Considerations”
(b) “The Negative Effect of Science and Technology”
(c) “Economic Considerations”
(d) “Recycling Issues in Materials Science and Engineering”
2 .Please mark “yes” or “no” in the brankets according to your knowleage or comprehension
(a) Materials science investigate the relationships between the structures and properties of
materials. ( )
(b) Materials engineering design or engineer the structure of a material to produce a
predetermined set of properties, on the basis of structure–property correlations.( )
(c) Materials science also pay attention to developing and using knowledge to understand
how the properties of materials can be controllably designed by varying the compositions,
structures.( )
(d) Materials Science and Engineering, only deal with how they can be adapted and
fabricated to meet the needs of modern technology.( )
3
．
Put the following words into English
温度系数；无定形态；延展性；基体；合金；屈服应力；应变；树脂；各向异性；变量；
强度；各向同性
4
．
Put the following words into Chinese
nanostructures；organic composites；elastomers；phase transformations；thermal stability；
superplastic；semiconductor chip；physical properties；ecological damage；metastable states；
supermolecular materials ； supersaturated solid solutions； amorphization；microstructural
features and properties.

Supplementary Reading

Composite Materials

Composite materials have been utilized to solve technological problems for a long time but
only in the 1960s did these materials start capturing the attention of industries with the
introduction of polymeric- based composites. Since then, composite materials have become
common engineering materials and are designed and manufactured for various applications
including automotive components , sporting goods, aerospace parts, consumer goods, and in the
marine and oil industries. The growth in composite usage also came about because of increased
awareness regarding product performance and increased competition in the global market for
lightweight components. Among all materials, composite materials have the potential to replace
widely used steel and aluminum, and many times with better performance. Replacing steel
components with composite components can save 60 to 80% in component weight, and 20 to 50%
weight by replacing aluminum parts. Today, it appears that composites are the materials of choice
for many engineering applications.
What Are Composites ?

A composite material is made by combining two or more materials to give a unique
combination of properties. The above definition is more general and can include metals alloys,
plastic co- polymers（共聚物）, minerals, and wood. Fiber- reinforced composite materials differ
from the above materials in that the constituent materials are different at the molecular level and
are mechanically separable. In bulk form, the constituent materials work together but remain in
their original forms. The final properties of composite materials are better than constituent
material properties.
The concept of composites was not invented by human beings; it is found in nature. An
example is wood, which is a composite of cellulose fibers （纤维素纤维）in a matrix of natural
glue called lignin.（木质素） The shell of invertebrates, such as snails and oysters, is an example
of a composite. Such shells are stronger and tougher than man-made advanced composites.
Scientists have found that the fibers taken from a spider’s web are stronger than synthetic fibers.
In India, Greece, and other countries, husks or straws mixed with clay have been used to build
houses for several hundred years. Mixing husk or sawdust in a clay is an example of a particulate
composite and mixing straws in a clay is an example of a short fiber composite. These
reinforcements are done to improve performance.
The main concept of a composite is that it contains matrix materials. The reinforcements can
be fibers, particulates, or whiskers, and the matrix materials can be metals, plastics, or ceramics.
The reinforcements can be made from polymers, ceramics, and metals. The fibers can be
continuous, long, or short. Composites made with a polymer matrix have become more common
and are widely used in various industries. This book focuses on composite materials in which the
matrix materials are polymer-based resins. They can be thermoset or thermoplastic resins（树脂）.

The reinforcing fiber or fabric provides strength and stiffness to the composite, whereas the
matrix gives rigidity and environmental resistance. Reinforcing fibers are found in different forms,
from long continuous fibers to woven fabric to short chopped fibers and mat. Each configuration
results in different properties. The properties strongly depend on the way the fibers are laid in the
composites. All of the above combinations or only one form can be used in a composite. The
important thing to remember about composites is that the fiber carries the load and its strength is
greatest along the axis of the fiber. Long continuous fibers in the direction of the load result in a
composite with properties far exceeding the matrix resin itself. The same material chopped into
short lengths yields lower properties than continuous fibers. Depending on the type of application
(structural or nonstructural) and manufacturing method, the fiber form is selected. For structural
applications, continuous fibers or long fibers are recommended; whereas for nonstructural
applications, short fibers are recommended. Injection and compression molding utilize short fibers,
whereas filament winding, pultrusion（拉挤成型）, and roll wrapping use continuous fibers.
Functions of Fibers and Matrix

A composite material is formed by reinforcing plastics with fibers. To develop a good
understanding of composite behavior, one should have a good knowledge of the roles of fibers and
matrix materials in a composite. The important functions of fibers and matrix materials are
discussed below.
The main functions of the fibers in a composite are:
• To carry the load. In a structural composite, 70 to 90% of the load is carried by fibers.
• To provide stiffness, strength, thermal stability, and other structural properties in t-he
composites.
• To provide electrical conductivity or insulation, depending on the type of fiber used.
A matrix material fulfills several functions in a composite structure, most of which are vital
to the satisfactory performance of the structure. Fibers in and of themselves are of little use
without the presence of a matrix material or binder. The important functions of a matrix material
include the following:
• The matrix material binds the fibers together and transfers the load to the fibers. It provides
rigidity and shape to the structure.
• The matrix isolates the fibers so that individual fibers can act separately. This stops or slows the
propagation of a crack.
• The matrix provides a good surface finish quality and aids in the production of net-shape or
near-net-shape parts.
• The matrix provides protection to reinforcing fibers against chemical attack and mechanical
damage (wear).
• Depending on the matrix material selected, performance characteristics such as ductility, impact
strength（冲击强度）, etc. are also influenced. A ductile matrix will increase the toughness of the
structure. For higher toughness requirements, thermoplastic-based composites are selected.
• The failure mode is strongly affected by the type of matrix material used in the composite as
well as its compatibility with the fiber.
Application in automotive industry

Composite materials have been considered the “material of choice” in some applications of

the automotive industry by delivering high-quality surface finish, styling details, and processing
options. Manufacturers are able to meet automotive requirements of cost, appearance, and
performance utilizing composites. Today, composite body panels have a successful track record in
all categories — from exotic sports cars to passenger cars to small, medium, and heavy truck
applications. In 2000, the automotive industry used 318 million pounds of composites. Because
the automotive market is very cost- sensitive, carbon fiber composites are not yet accepted due to
their higher material costs. Automotive composites utilize glass fibers as main reinforcements.

Reference :Mazumdar, Sanjay K. Composites manufacturing : materials,
product, and process engineering, CRC Press LLC,2002:3-6

Part Ⅱ METALLIC MATERLALS AND ALLOYS
Unit 5
Text
An Introduction to Metallic Materials
A metal is a chemical element that is a good conductor of both electricity
and heat, forms cations and ionic bonds with non-metals. In chemistry, a
metal (Ancient Greek métallon, μέταλλον) is an element, compound, or alloy
characterized by high electrical conductivity. In a metal, atoms readily lose
electrons to form positive ions (cations). Those ions are surrounded by
delocalized electrons, which are responsible for the conductivity. The solid thus
produced is held by electrostatic interactions between the ions and the electron
cloud, which are called metallic bonds.
Definition
Metals are sometimes described as an arrangement of positive ions
surrounded by a cloud of delocalized electrons. They are one of the three groups
of elements as distinguished by their ionization and bonding properties, along
with the metalloids and non-metals.
Metals occupy the bulk of the periodic table, while non-metallic elements
can only be found on the right-hand-side of the Periodic Table of the
Elements. A diagonal line drawn from boron (B) to polonium (Po) separates
the metals from the nonmetals. Most elements on this line are metalloids,
sometimes called semiconductors. This is due to the fact that these elements
exhibit electrical properties common to both conductors and insulators.
Elements to the lower left of this division line are called metals, while elements
to the upper right of the division line are called non-metals.
An alternative definition of metal refers to the band theory. If one fills the













metallic bonds
mi tlik bnd
n.金属键

Metalloids
metlid
n.类金属
non-metals
nn metl
n.非金属

Periodic Table of the Elements
元素周期表

energy bands of a material with available electrons and ends up with a top band
partly filled then the material is a metal. This definition opens up the category for
metallic polymers and other organic metals, which have been made by
researchers and employed in high-tech devices. These synthetic materials often




have the characteristic silvery-grey reflectiveness (luster) of elemental metals
Properties
Chemical
Metals are usually inclined to form cations through electron loss, reacting
with oxygen in the air to form oxides over changing timescales (iron rusts over
years, while potassium burns in seconds). Examples:
4 Na + O2 → 2 Na2O (sodium oxide)
2 Ca + O2 → 2 CaO (calcium oxide)
4 Al + 3 O2 → 2 Al2O3 (aluminium oxide)
The transition metals (such as iron, copper, zinc, and nickel) take much
longer to oxidize. Others, like palladium, platinum and gold, do not react with
the atmosphere at all. Some metals form a barrier layer of oxide on their surface
which cannot be penetrated by further oxygen molecules and thus retain their
shiny appearance and good conductivity for many decades (like aluminium,
some steels, and titanium). The oxides of metals are generally basic, as
opposed to those of nonmetals, which are acidic.
Painting, anodising or plating metals are good ways to prevent their
corrosion. However, a more reactive metal in the electrochemical series must
be chosen for coating, especially when chipping of the coating is expected. Water
and the two metals form an electrochemical cell, and if the coating is less
reactive than the coatee, the coating actually promotes corrosion.
Physical









transition metals
trnzin
n.过度金属








electrochemical cell
lektr`kemkl
电化学池


sel

Fig.5.1 Gallium crystals
Metals in general have high electrical conductivity, thermal conductivity,
luster and density, and the ability to be deformed under stress without cleaving.
While there are several metals that have low density, hardness, and melting
points, these (the alkali and alkaline earth metals) are extremely reactive, and
are rarely encountered in their elemental, metallic form. Optically speaking,
metals are opaque, shiny and lustrous. This is due to the fact that visible
lightwaves are not readily transmsitted through the bulk of their microstructure.
The large number of free electrons in any typical metallic solid (element or alloy)
is responsible for the fact that they can never be categorized as transparent
materials.
The majority of metals have higher densities than the majority of
nonmetals. Nonetheless, there is wide variation in the densities of metals; lithium
is the least dense solid element and osmium is the densest. The metals of groups
I A and II A are referred to as the light metals because they are exceptions to this
generalization. The high density of most metals is due to the tightly- packed
crystal lattice of the metallic structure. The strength of metallic bonds for
different metals reaches a maximum around the center of the transition series, as
those elements have large amounts of delocalized electrons in a metallic bond.
However, other factors (such as atomic radius, nuclear charge, number of
bonding orbitals, overlap of orbital energies, and crystal form) are involved as
well.
Electrical















transparent materials
trns prnt
mtrl
透明材料

The electrical and thermal conductivity of metals originate from the fact that
in the metallic bond, the outer electrons of the metal atoms form a gas of nearly

free electrons, moving as an electron gas in a background of positive charge free electron model
formed by the ion cores. Good mathematical predictions for electrical 
conductivity, as well as the electrons' contribution to the heat capacity and heat

conductivity of metals can be calculated from the free electron model, which 自由电子模型

does not take the detailed structure of the ion lattice into account.
When considering the exact band structure and binding energy of a metal, it
is necessary to take into account the positive potential caused by the specific
arrangement of the ion cores - which is periodic in crystals. The most important
consequence of the periodic potential is the formation of a small band gap at
the boundary of the Brillouin zone. Mathematically, the potential of the ion
cores can be treated by various models, the simplest being the nearly-free
electron model.
Mechanical
Mechanical properties of metals include their ductility, which is largely
due to their inherent capacity for plastic deformation. Thus, elasticity in
metals can be described by Hooke's Law for restoring forces, where the stress
is linearly proportional to the strain. Larger forces in excess of the elastic limit
may cause a permanent (irreversible) deformation of the object. This is what is
known in the literature as plastic deformation -- or plasticity. This irreversible
change in atomic arrangement may occur as a result of either (or both) of the
following factors:
The action of an applied force (or work)
A change in temperature (or heat).

ion cores
 
n.离子实

band gap
 
n.能隙

brillouin zone
 
n.布里渊区

ductility

n.延展性
plastic deformation


塑性变形

elastic limit
 

Fig.5.2 Hot metal work from a blacksmith
In the former case, the applied force may be tensile (pulling) force,
compressive (pushing) force, shear, bending or torsion (twisting) forces. In
the latter case, the most significant factor which is determined by the temperature
is the mobility of the structural defects such as grain boundaries, point
vacancies, line and screw dislocations, stacking faults and twins in both
crystalline and non-crystalline solids. The movement or displacement of such
mobile defects is thermally activated, and thus limited by the rate of atomic
diffusion.
Viscous flow near grain boundaries, for example, can give rise to internal
slip, creep, fatigue in metals. It can also contribute to significant changes in the
microstructure like grain growth and localized densification due to the
elimination of intergranular porosity. Screw dislocations may slip in the
direction of any lattice plane containing the dislocation, while the principal
driving force for diffusion of vacancies
through a crystal lattice.
In addition, the nondirectional nature of metallic bonding is also thought to
contribute significantly to the ductility of most metallic solids. When the planes
of an ionic bond slide past one another, the resultant change in location shifts
ions of the same charge into close proximity, resulting in the cleavage of the
crystal. Such shift are not observed in covalently bonded crystals where fracture
and crystal fragmentation occurs.
❖弹性极限














viscous flow
❖ 
n.黏性流动



screw dislocations


n.螺旋位错
lattice plane
 
n.晶面
crystal lattice

Alloys
An alloy is a mixture of two or more elements in solid solution in which
the major component is a metal. Most pure metals are either too soft, brittle or
chemically reactive for practical use. Combining different ratios of metals as
alloys modifies the properties of pure metals to produce desirable characteristics.
The aim of making alloys is generally to make them less brittle, harder, resistant
to corrosion, or have a more desirable color and luster. Of all the metallic alloys
in use today, the alloys of iron (steel, stainless steel, cast iron, tool steel,
alloy steel) make up the largest proportion both by quantity and commercial
value. Iron alloyed with various proportions of carbon gives low, mid and high
carbon steels, with increasing carbon levels reducing ductility and toughness. The
addition of silicon will produce cast irons, while the addition of chromium,
nickel and molybdenum to carbon steels (more than 10%) results in stainless
steels.
Other significant metallic alloys are those of aluminium, titanium, copper
and magnesium. Copper alloys have been known since the Bronze Age, and
have many applications today, most importantly in electrical wiring. while the
alloys of the other three metals have been developed relatively recently -
chemical reactivity of these metals, requires modern electrolytic extraction
processes. The alloys of aluminium, titanium and magnesium are also known and
valued for their high strength-to- weight ratios and, in the case of magnesium, for
the ability to provide electromagnetic shielding. These materials are ideal for
situations where high strength-to-weight ratios are more important than bulk cost,
such as in aerospace and in certain automotive applications.
Alloys specially designed for highly demanding applications, such as jet
engines, may contain more than ten elements.
 
n.晶格



























Categories
Base metal

In chemistry, the term 'base metal' is used informally to refer to a metal
that oxidizes or corrodes relatively easily, and reacts variably with dilute base metal
hydrochloric acid (HCl) to form hydrogen. Examples include iron, nickel, lead  
and zinc. Copper is considered a base metal as it oxidizes relatively easily, n.母材，基材
although it does not react with HCl. It is commonly used in opposition to noble
metal.
In alchemy, a base metal was a common and inexpensive metal, as opposed
to precious metals, mainly gold and silver. A longtime goal of the alchemists
was the transmutation of base metals into precious metals.
In numismatics, coins used to derive their value primarily from the
precious metal content. Most modern currencies are fiat currency, allowing the
coins to be made of base metal.
Ferrous metal
The term is derived from the Latin word meaning
ironwrought iron, or an alloy such as steel.
Ferrous metals are often magnetic, but not exclusively.
Noble metal
Noble metals are metals that are resistant to corrosion or oxidation, unlike
most base metals. They tend to be precious metals, often due to perceived
rarity. Examples include tantalum, gold, platinum, silver and rhodium. Noble
metals are metals that are resistant to corrosion and oxidation in moist air,
unlike most base tend to be precious, often due to the rarity in the
Earth's crust. The noble metals are considered to be (in order of increasing
atomic number) ruthenium, rhodium, palladium, silver, osmium, iridium,
platinum, gold .
Other sources include mercuryor even rhenium as a noble metal. On the
other hand, neither titanium nor niobium nor tantalum are called noble metals
despite the fact that they are very resistant to corrosion.
Noble metals should not be confused with precious metals (although many







ferrous metals
 
黑色金属


noble metals
 
贵金属

noble metals are precious).

Fig.5.3 The noble metals including mercury and rhenium together with the non-noble
metal copper ordered according their position in the periodic table of the elements
Precious metal
A precious metal is a rare metallic chemical element of high economic
value.
Chemically, the precious metals are less reactive than most elements, have
high luster and high electrical conductivity. Historically, precious metals were
important as currency, but are now regarded mainly as investment and industrial
commodities. Gold, silver, platinum and palladium each have an ISO 4217
currency code. The best-known precious metals are gold and silver. While both
have industrial uses, they are better known for their uses in art, jewelry, and
coinage. Other precious metals include the platinum group metals: ruthenium,
rhodium, palladium, osmium, iridium, and platinum, of which platinum is the
most widely traded. Plutonium and uranium could also be considered precious
metals.

Fig.5.4 A gold nugget














precious metals
 
贵重金属

The demand for precious metals is driven not only by their practical use, but
also by their role as investments and a store of value. Palladium was, as of
summer 2006, valued at a little under half the price of gold, and platinum at
around twice that of gold. Silver is substantially less expensive than these metals,
but is often traditionally considered a precious metal for its role in coinage and





jewelry.
Metals are sometimes described as an arrangement of positive ions
surrounded by a cloud of delocalized electrons. They are one of the three groups
of elements as distinguished by their ionization and bonding properties, along
with the metalloids and non- metals.
Applications
Some metals and metal alloys possess high structural strength per unit mass,
making them useful materials for carrying large loads or resisting impact damage.
Metal alloys can be engineered to have high resistance to shear, torque and
deformation. However the same metal can also be vulnerable to fatigue damage
through repeated use or from sudden stress failure when a load capacity is
exceeded. The strength and resilience of metals has led to their frequent use in
high- rise building and bridge construction, as well as most vehicles, many
appliances, tools, pipes, non-illuminated signs and railroad tracks.
The two most commonly used structural metals, iron and aluminium, are
also the most abundant metals in the Earth's crust.
Metals are good conductors, making them valuable in electrical appliances
and for carrying an electric current over a distance with little energy lost.
Electrical power grids rely on metal cables to distribute electricity. Home
electrical systems, for the most part, are wired with copper wire for its good
conducting properties.
The thermal conductivity of metal is useful for containers to heat materials
over a flame. Metal is also used for heat sinks to protect sensitive equipment
from overheating.













vulnerable
❖
adj.易损

The high reflectivity of some metals is important in the construction of heat sinks
mirrors, including precision astronomical instruments. This last property can also  
make metallic jewelry aesthetically appealing.
Some metals have specialized uses; radioactive metals such as uranium
and plutonium are used in nuclear power plants to produce energy via nuclear
fission. Mercury is a liquid at room temperature and is used in switches to radioactive metals
n.热沉材料

complete a circuit when it flows over the switch contacts. Shape memory alloy
is used for applications such as pipes, fasteners and vascular stents.

Notes
1. Metals are sometimes described as an arrangement of positive ions surrounded
by a cloud of delocalized electrons. They are one of the three groups of elements
as distinguished by their ionization and bonding properties, along with the
metalloids and non-metals.
金属往往被描述为被离域电子云包 围的阳离子排列。根据金属的电离特
性和成键特性可以将金属与类金属和非金属区分开来。
2. Metals in general have high electrical conductivity, thermal conductivity,
luster and density, and the ability to be deformed under stress without cleaving.
一般说来，金属具有高电导性、高导热性、高光 泽、高密度和在一定应
力状态下不断裂的变形能力。
3. When considering the exact band structure and binding energy of a metal, it is
necessary to take into account the positive potential caused by the specific
arrangement of the ion cores - which is periodic in crystals.
当涉及金属精确的能带结构和结合能时，有必要 考虑晶体中周期排列的
特殊离子实所引起的正电势。
4. The alloys of aluminium, titanium and magnesium are also known and valued
for their high strength-to-weight ratios and, in the case of magnesium, for the
ability to provide electromagnetic shielding.
❖

n.放射性金属

铝合金，钛合金和镁合金由于高的比强度而被人们熟知和认可，至于镁合金，还具有提供电磁屏蔽的能力。
5. The strength and resilience of metals has led to their frequent use in high-rise
building and bridge construction, as well as most vehicles, many appliances,
tools, pipes, non-illuminated signs and railroad tracks.
金属材料强度高、韧性好而常用于高层建筑和桥梁建筑，也可用于 众多
交通工具，仪表，机床，管道，非照明式标志和铁路轨道上。

Exercises
1. Choose correct choice for each question according to the text

（1）According to the text, elements to the lower left of the diagonal line in the
Periodic Table of the Elements are called .
A. nonmetals; B. metals; C. semiconductors; D. insulators
（2）Mechanical properties of metals include their ductility, which is largely due
to their inherent capacity for .
A. elastic deformation; B. plastic deformation; C. slip deformation; D. alloys
（3）Chemically, the which is a rare metallic chemical element of
high economic value is less reactive than most elements, has high luster and
high electrical conductivity.
A. precious metal; B. noble metal; C. ferrous metals; D. base metal
2. Translate the following into English
合金是由两种或两种以上的元素在固溶下组成且主要成份是金属的物质。
3. Translate the following into Chinese
Screw dislocations may slip in the direction of any lattice plane containing
the dislocation, while the principal driving force for climbis the
movement or diffusion of vacancies through a crystal lattice.

























Supplementary Reading
Steel

Steel is an alloy consisting mostly of iron, with a carbon content between
0.2% and 2.1% by weight, depending on the grade. Carbon is the most
cost-effective alloying material for iron, but various other alloying elements are
used such as manganese, chromium, vanadium, and tungsten. Carbon and
other elements act as a hardening agent, preventing dislocations in the iron atom

crystal lattice from sliding past one another. Varying the amount of alloying
elements and form of their presence in the steel (solute elements, precipitated
phase) controls qualities such as the hardness, ductility, and tensile strength
of the resulting steel. Steel with increased carbon content can be made harder and
stronger than iron, but is also less ductile. solute element
Alloys with a higher carbon content are known as cast iron because of 
their lower melting point and is also distinguished from
wrought iron, which can contain a small amount of carbon, but it is included in
the form of slag inclusions. Two distinguishing factors are steel's increased
rust-resistance and better weldability.
Though steel had been produced by various inefficient methods long before
the Renaissance, its use became more common after more efficient production
methods were devised in the 17th century. With the invention of the Bessemer
process in the mid-19th century, steel became a relatively inexpensive
mass- produced material. Further refinements in the process, such as basic
oxygen steelmaking, further lowered the cost of production while increasing
the quality of the metal. Today, steel is one of the most common materials in the
world and is a major component in buildings, infrastructure, tools, ships,
automobiles, machines, and appliances. Modern steel is generally identified by
various grades of steel defined by various standards organizations.
When iron is smelted from its ore by commercial processes, it contains more
carbon than is desirable. To become steel, it must be melted and reprocessed to
reduce the carbon to the correct amount, at which point other elements can be
added. This liquid is then continuously cast into long slabs or cast into ingots.
96% of steel is continuously cast, while only 4000 ingots are cast per year. The
ingots are then heated in a soaking pit and hot rolled into slabs, blooms, or
billets. Slabs are hot or cold rolled into sheet metal or plates. Billets are hot or
cold rolled into bars, rods, and wire. Blooms are hot or cold rolled into structural
steel, such as I-beams and rails. In modern foundries these processes often

溶质元素
precipitated phase


析出相

tensile strength
 
抗拉强度


cast iron
 
铸铁
wrought iron
 
熟铁，锻铁


Bessemer process
 
贝塞麦炼钢法

occur in one assembly line, with ore coming in and finished steel coming out.
Sometimes after a steels final rolling it is heat treated for strength, however this is
relatively rare.
It is common today to talk about
single entity, but historically they were separate products. The steel industry is
often considered to be an indicator of economic progress, because of the critical
role played by steel in infrastructural and overall economic development.
The economic boom in China and India has caused a massive increase in
the demand for steel in recent years. Between 2000 and 2005, world steel demand
increased by 6%. Since 2000, several Indian and Chinese steel firms have risen to
prominence like Tata Steel (which bought Corus Group in 2007), Shanghai
Baosteel Group Corporation and Shagang Group. ArcelorMittal is however
the world's largest steel producer.
The British Geological Survey reports that in 2005, China was the top
producer of steel with about one-third world share followed by Japan, Russia,
and the USA.
In 2008, steel started to be traded as a commodity in the London Metal
Exchange. At the end of 2008, the steel industry faced a sharp downturn that led
to many cut-backs.

Unit 6


Text

Metal Manufacturing Methods

Metal manufacturing methods are techniques by which metals and alloys are
formed or processed into products. The manufacturing methods include many
techniques, such as liquid moulding (like casting), forming operation (forging,
rolling), joint technology (welding), powder metallurgy, etc. The methods using
depends on the nature of the metal, the shape of the termination product, and, of
cause, cost. In this unit, some representative metal methods, as well as their
advantages and disadvantages are briefly introduced.
1. Liquid moulding technique---Casting
Casting is a process that pouring molten metal into a mold, after
solidification, a semi-finished product (or cast part) with certain shape, dimension,
and property was obtained. Casting is one of the most fundamental techniques,
which is suitable for those metals possess superior flowability, relatively low
shrinking percentage, and so on. Casting is also the oldest metal hot-working
technique. Take China as an example, the bronze casting was so boomed in China
during the 13
th
-10
th
B.C.
According to the different mold, this technique includes sand, investment and
die casting, etc.
 Sand casting
Sand casting is characterized by economical and operationally simply. For

















solidificationslidifikei
nn.凝固
flowabilityflubiliti
n.流动性

sand casting, ordinary sand is always used as the mold material. The two- piece
mold is usually formed by packing sand around a model which has the desired
shape. In addition, a gating system is usually incorporated into the mold in order to
drive the molten metal into the cavity more fluently. So that the internal casting
defects could be minimized. Though convenient, sand casting has several intrinsic
drawbacks. Such as comparatively high defective rate and high surface roughness.
 Investment casting

intrinsicintrinsik
Investment casting (also called lost-wax casting) is a casting method in which adj.固有的, 内在的
the low-melting fusible wax or plastic pattern is used. In investment casting, the
wax pattern is dipped into ceramic slurry, drained and coated with fine ceramic
refractory. Then the pattern is dried and the mould or mold investment is formed.
The investment is then heated, so that the pattern melts and the wax runs out. waxwksn.蜡
Molten metal is poured into the mold to form the cast part. Investment casting is
always adopted when smooth surface, accurate dimension, as well as high refractoryrifrktri
geometrical precision is demanded. This method can also meet the requirement of n.耐火材料
complicated and thin-wall cast parts.
 Die casting


Die casting (sometimes called pressure casting) is a process of casting metal
under pressure, to produce castings that have lower porosity than sand casting.
During solidification, the pressure is maintained. Usually a steel mold or die pairs
are employed in die casting. Die castings are generally characterized by good porosityprsiti n.多孔性
surface finish and good dimensional accuracy. Furthermore, die casting is an
inexpensive method due to its rapid casting rate and low defective rate. In industry,
the stronger and harder metals such as iron and steel cannot be die-cast. On the
contrary, Aluminum, Zinc and Copper alloys are the materials predominantly used
in die-casting.
2. Forming Operations


Forming operations are the techniques in which the shape of a metal piece is predominantlypridmin
changed by plastic deformation, including forging, rolling, extrusion, drawing, and ntli

so on.
 Forging
adv.主要的，大部分的







(a) (b)
Figure 1. Schematic of hot forging
(a) closed-die forging; (b) open-die forging (cited from )





Forging is a process that deforming a single piece of hot metal by means of
metal forming machinery. Forgings are classified as cold and hot forging,
according to the ingot temperature during process. For cold forging, the ingot is
usually maintained at room-temperature. For hot forging, on the other hand, the
temperature is usually higher than the recrystallization temperature of the ingot.
Hot forging is more common and includes closed-die and open-die forging. For
closed- die, a force is brought to bear on a metal slug or preform placed between schematicskimtik
two or more die halves. The metal flows plastically into the cavity formed by the n.图表，示意图
die and hence changes in shape to its finished shape (Figure 1a). Open-die forging
is performed between flat dies with no pre-cut profiles. The dies do not confine the forgingn.锻造
metal laterally during forging. Deformation is achieved through movement of the
workpiece relative to the dies. Parts up to thirty metres in length can be hammered
or pressed into shape in this way. Open-die forging comprises many process recrystallizationrikristl
variations, enabling an extremely broad range of shapes and sizes to be produced
lzein
(Figure 1b). The forged articles have excellent mechanical properties, combining n.再结晶
fine grain structure with strengthening through strain hardening. For example, the
porosity of the as-cast articles can be removed by forging.
 Rolling

Rolling is one of the most widely used deformation process. It consists of
passing metal between two rollers, which exert compressive stresses, reducing the
metal thickness. Where simple shapes are to be made in large quantity, rolling is
the most economical process. Rolled products include sheets, structural shapes and
rails as well as intermediate shapes for wire drawing or forging. Circular shapes,
‘I’ beams and railway tracks are manufactured using grooved rolls.


Figure 2. Schematic of rolling (cited from )
Initial breakdown of an ingot or a continuously cast slab is achieved by hot
rolling. Mechanical strength is improved and porosity is reduced. The worked
metal tends to oxidize leading to scaling which results in a poor surface finish and
loss of precise dimensions. A hot rolled product is often pickled to remove scale,
and further rolled cold to ensure a good surface finish and optimize the mechanical
properties for a given application. Cold rolling is often used in the final stages of
production. Sheets, strips and foils are cold rolled to attain dimensional accuracy
and high quality surface finishes.
 Extrusion
In extrusion, a bar of metal is forced from an enclosed cavity via a die orifice
by a compressive force applied by a ram. Since there are no tensile forces, high
deformations are possible without the risk of fracture of the extruded material. The
extruded article has the desired, reduced cross-sectional area, and also has a good
surface finish so that further machining is not needed. Extrusion products include
rods and tubes with varying degrees of complexity in cross-section.





rollingrn.碾压

Figure 3. Schematic of extrusion (cited from )


Hot extrusion is carried out at a temperature of approximately 0.6T
m
and the
extrusion
pressures required range from 35 to 700 MPa. While, cold extrusion is performed
n.挤出
at temperatures significantly below the melting temperature of the alloy being

deformed, and generally at room temperature.
 Drawing


Drawing is the pulling of a metal piece through a die by means of a tensile

force applied to the exit side. A reduction in cross- sectional area results, with a

corresponding increase in length. A complete drawing apparatus may include up to

twelve dies in a series sequence, each with a hole a little smaller than the

preceding one. In multiple-die machines, each stage results in an increase in length

and therefore a corresponding increase in speed is required between each stage.

Metals can be formed to much closer dimensions by drawing than by rolling.

Shapes ranging in size from the finest wire to those with cross-sectional areas of

many square centimetres can be commonly drawn. Drawn products include wires,

rods and tubing products. Large quantities of steel and brass are cold drawn.

Seamless tubing can be produced by cold drawing when thin walls and very

accurate finishes are required.

drawingn.拉拔





Figure 4. Schematic of drawing (cited from )
 Stamping



Stamping is used to make high volume parts such as aviation or car panels or

electronic components. Mechanical or hydraulic powered presses stamp out parts

from continuous sheets of metal or individual blanks. The upper die is attached to

the ram and the lower die is fixed. Whereas mechanical machinery transfers all
seamlesssimlisadj.无缝
energy as a rapid punch, hydraulic machinery delivers a constant, controlled force.
的








Figure 5. Schematic of stamping (cited from )
3. Welding



Welding, differed from rivet and screw fasten, is a joint method in which
stampingstmpin.冲压
atomic bonding occurs between two metal pieces. Welding is mainly employed to

manufacture metallic hardware. For example, boiler, pressure container, pipeline,
hydraulichdrlikad
ship craft, vehicle, aircraft, etc are always produced by welding. Welding is needed
j.液力的，液压的
in almost all industrial fields. Over 60% of annually steel output is produced by

welding in some important industrialized nations.
Welding has been extensively used due to a series of advantages. Firstly,
welding can produce articles with excellent joint properties. The welding seam is
characterized by good leak tightness, conductivity, wear and corrosion-resistance.
Secondly, compared with rivet, welding is more economical. About 10-20%
metallic materials can be saved if rivet is taken place by welding. Thirdly, the
weight of metallic hardware can be reduced by welding, which is quite important
for launch vehicles like ship craft, rocket, etc. Finally, the manufacturing
procedure can be significantly simplified by welding, especially for heavy and
complicated pieces.
A variety of welding methods exist, including arc, gas, plasma arc and laser
beam welding.
Arc welding usually uses electric arc as heat source to melt solder wire. It is
the most fundamental and extensive welding technique. Gas welding, also called
gas shielded welding, uses external gas as the arc dielectric to protect the molten
droplet, pool, and seam from oxidization. Gases generally adopted such as inert
gas (argon or helium) or high-intensity gas (carbon dioxide). Plasma arc welding is
another advanced technique. The plasma arc is always generated between a
tungsten cathode and anode. It is an electric arc with high- temperature,
high-ionization and high energy- density. Laser beam welding is a relatively
modern joint technique, in which a highly focused and intense laser beam is used
as the heat source. The laser beam melts the weldment, and upon solidification, a
fusion joint is produced. The power density of the laser beam is so high that metals
can be melted in extremely short time.
4. Powder metallurgy
Powder metallurgy is sintering process for making various parts out of
powders of high melting-point metal or alloy. Both technical and economic
advantages are gained by using this method of fabrication. In powder metallurgy,
the metal powder is compacted by placing in a closed metal cavity (the die) under








plasmaplzmn.等离子
体



dielectricdiilektrikn.
介质



cathodekudn.阴极

pressure. This compacted material is placed in an oven and sintered in a controlled
atmosphere at high temperature and the metal powders coalesce and form a solid.
As a branch of metallurgy, powder metallurgy is generally employed to produce
high-quality materials which are difficult or not able to be achieved through fusion metallurgymetldi
casting. Powder metallurgy is also useful in making parts that have irregular n.冶金，冶金学，冶金术
curves, or recesses that are hard to machine. It is suitable for high volume
production with very little wastage of material. Secondary machining is virtually
eliminated. Combining unique technical features with cost effectiveness, powder
metallurgy components have been used in ever increasing quantities in a wide
variety of industries. Typical components that can be made with this process
include cams, ratchets, sprockets, sintered bronze and iron bearings and carbide
tool tips.

recessrisesn.凹槽，凹坑




camkmn.凸轮
ratchetrtitn.单向齿轮
sprocketsprtikn.链齿，星
轮


Notes
1. Metal manufacturing methods are techniques by which metals and alloys are formed or
processed into products. The manufacturing methods include many techniques, such as liquid
moulding (like casting), forming operation (forging, rolling), joint technology (welding),
powder metallurgy, etc.
金属的制备方法是指使金属或合金产生变 形，或对其进行处理，以获得所需产品的技术。

主要包括液态成型技术（如铸造），形变 技术（如锻造、轧制等），连接技术（如焊接等），
以及粉末冶金技术等。
2. In investment casting, the wax pattern is dipped into ceramic slurry, drained and coated with
fine ceramic refractory. Then the pattern is dried and the mould or mold investment is formed.
The investment is then heated, so that the pattern melts and the wax runs out. Molten metal is
poured into the mold to form the cast part. 熔模铸造中，首先将蜡模浸入陶瓷浆液中，干燥后使蜡模表面涂覆上一层细陶瓷耐火材
料，得到围模 。然后，将围模加热，使蜡模熔化并流掉，剩下的即为所得模具。此时将
熔融金属倒入耐高温模具中，则 可得到所需铸件。
3. Gas welding, also called gas shielded welding, uses external gas as the arc dielectric to
protect the molten droplet, pool, and seam from oxidization. Gases generally adopted such as
inert gas (argon or helium) or high-intensity gas (carbon dioxide).
气焊（又称气体保护 焊）通常使用外加气体作为电弧介质，并保护电弧区的熔滴和熔池
及高温的焊缝金属。保护气体通常有两 种：一种是惰性气体（如氩气和氦气），另一种
是高密度的气体（如二氧化碳）。
Exercises
1. Choose correct choice for each question according to the text
（1）Compared with investment castings, the surface finish of sand castings is
A. better; B. worse; C. the same; D. more better
（2）The heat source in arc welding is
A. electric arc; B. inert gas; C. plasma arc; D. laser beam
（3）Among the metal manufacturing methods, which of the following is suitable to produce
carbide tools?
A. Casting; B. Forging; C. Drawing; D. Powder metallurgy
2. Translate the following into English
粉末冶金一般用于生产使用熔铸技术较难或无法生产的高熔点材料。
3. Translate the following into Chinese
Metals can be formed to much closer dimensions by drawing than by rolling. Shapes ranging in
size from the finest wire to those with cross-sectional areas of many square centimetres can be
commonly drawn.

Supplementary Reading
Art Casting in China: History and Future
The Chinese art casting with 5000 years history had motivated the development of casting in
whole world. The difference between ancient and modern art casting is mainly lied in casting
methods, as well as mould materials.
The early bronze forming technique is mainly the pottery mould (loan mould) casting in
which a split casting mould composed of several piece- moulds is used. Each piece-mould is made
through clay-refining and staling processes. The mould material is a mixture of fine-clay filtered
by water, plant ash and chamotte. The individual piece-moulds are reassembled, to which the
mixture of grass and clay is applied (instead of sand-box). After dried in the shade, the split mould
is fired in the kiln, and taken out before becoming vitrified. When the split mould is cooled to a
special temperature, the molten metal can be poured into the mould. In this method, very fine
patterns can be exposed on bronze castings, by replicating or sculpturing them onto the
piece-mould. Moreover, those ancient artisans hold the adept skills, as well as some techniques
such as multiple piece-mould method, separate casting and connecting casting are applied, and
hence the vessels with quite intricate configuration and exquisite patterns can be cast. For example,
the Four-Goat Zun (shown in Fig. 1) with a height of 58.3 cm was cast using separate casting
technique. The goat horns were firstly cast, and then embedded in the goat head piece-moulds.
When the Zun body was cast, the horns would hang together with the goat heads. The casting
traces and parting lines at the joint of goat head and horn as well as zun body could not be almost
recognized. And this Four-Goat Zun was ever thought to be formed through lost wax casting.

Figure 1. Four-Goat Zun
The earliest lost wax castings appeared in China 2600 years ago. In the excellence concerning
lost wax technique, the Chinese artisans created many art castings with high degree of technical
difficulty. In the traditional lost wax casting, the used wax material includes beeswax, colophony
and fattiness of animal and plant, whose percentage is usually adjusted based on the requirement
on air temperature and hardness. The slurry used for casting mould is similar to that in the pottery
moulding. The wax pattern is modeled by hand rather than using mould. This traditional craft was
still in application till the end of last century. More than 2000 years ago, some casting techniques
such as cluster casting and permanent mould casting were also adopted in China. These techniques
were significantly superb and widely used for producing coins, tools, weapons, chariots and
horses.
From the late 19
th
to middle 20
th
century, even though both sculptors studying abroad and
skill-training workshops run by church ever introduced some western techniques concerning art
casting to China, the art casting industry of China showed a declining trend due to societal
turbulence and economic limitation. Until the eighties of the 20
th
century, the art casting industry
in China got rapidly developed with the reform and open. The Art Casting Technical Committee of
China Foundry Association was founder in 1998. The used techniques include the traditional loam
casting, resin sand casting, water glass sand casting, plaster-mould investment casting,
plaster-mould negative pressure casting, full- mould casting, multiple-shell investment casting,
pottery-mould casting, mould-mould casting, die casting, heat-resistant glue centrifugal casting.
Besides the traditional bronze and brass, such alloys as cupronickel, tin-bronze, ormolu, zinc alloy,
stainless steel, tin alloy, cast iron, titanium alloy and gold-base alloy are also applied. For more

than ten years, some large art castings have been made. In the early 1990s, a seater Buddha statue
with a height of 26.4 m, named the Tiantan Buddha, was built in Hong Kong. Subsequently, the
Lingshan Buddha with a height of 88 m was cast in Wuxi during the 1990s. In 2003, the wrought
copper Fushan Gold Buddha with a height of 128 m was constructed in Henan. These large art
castings with Chinese cultural characteristics are actually the direct testimony of rapid
development of art casting industry in China.
Both quantity and size of Chinese art castings have ascended to the forefront in the world. The
exterior effect, however, demands improving, to keep up a pace of our ancestor.



Part Ⅱ METALLIC MATERLALS AND ALLOYS

Unit 7
Text

Structure of Metallic Materials
Solid materials may be classified according to the regularity with which atoms or ions
are arranged with respect to one another. A crystalline material is one in which the atoms are
situated in a repeating or periodic array over large atomic distances; that is, long-range order
exists, such that upon solidification, the atoms will position themselves in a repetitive
three-dimensional pattern, in which each atom is bonded to its nearest-neighbor atoms. All
metals, many ceramic materials, and certain polymers form crystalline structures under normal
solidification conditions. For those that do not crystallize, this long-range atomic order is
absent.
Some of the properties of crystalline solids depend on the crystal structure of the
material, the manner in which atoms, ions, or molecules are spatially arranged. There is an
extremely large number of different crystal structures all having long range atomic order; these
vary from relatively simple structures for metals, to exceedingly complex ones, as displayed by





crystallinekristlainadj.晶
solidificationsl idfikei
n.凝固
repetitive ripetitiv
重复的，反复性的
crystal structure 晶体结构
spatially speili adv. 空
地

some of the ceramic and polymeric materials. The present discussion deals with several atomic hard sphere model
common metallic crystal structures. 刚球模型
When describing crystalline structures, atoms (or ions) are thought of as being solid
spheres having well-defined diameters. This is termed the atomic hard sphere model in which lattice ltis n. 点阵
spheres representing nearest-neighbor atoms touch one another. An example of the hard sphere
model for the atomic arrangement found in some of the common elemental metals is displayed
in Figure 7.1c. In this particular case all the atoms are identical. Sometimes the term lattice is
used in the context of crystal structures; in this sense ‘‘lattice’’ means a three-dimensional
array of points coinciding with atom positions (or sphere centers).
The atomic order in crystalline solids indicates that small groups of atoms form a
repetitive pattern. Thus, in describing crystal structures, it is often convenient to subdivide the
structure into small repeat entities called unit cells. Unit cells for most crystal structures are
parallelepipeds or prisms having three sets of parallel faces; one is drawn within the
aggregate of spheres (Figure 7.1c), which in this case happens to be a cube. A unit cell is
chosen to represent the symmetry of the crystal structure, wherein all the atom positions in the
crystal may be generated by translations of the unit cell integral distances along each of its
edges. Thus, the unit cell is the basic structural unit or building block of the crystal structure
and defines the crystal structure by virtue of its geometry and the atom positions within.
Convenience usually dictates that parallelepiped corners coincide with centers of the hard
sphere atoms. Furthermore, more than a single unit cell may be chosen for a particular crystal
structure; however, we generally use the unit cell having the highest level of geometrical
symmetry.

Figure

7.1 For the
face
-
centered
cubic crystal structure: (a) a hard sphere unit cell representation, (b)



unit cells 晶胞
parallelepipeds
prlelepipedn.平行六面体
prisms prizmn.棱柱
symmetry simitri n.对称性
translationstrnsleinn
移
geometry dimitrin. 几
（学）







nondirectional
nndireknln.无方
的，适合各方向的

a reduced-
sphere
unit cell, and (c) an aggregate of many atoms.

The atomic bonding in this group of materials is metallic, and thus nondirectional in


nature. Consequently, there are no restrictions as to the number and position of

nearest-neighbor atoms; this leads to relatively large numbers of nearest neighbors and dense

atomic packings for most metallic crystal structures. Also, for metals, using the hard sphere


model for the crystal structure, each sphere represents an ion core. Table 7.1 presents the
atomic radii for a number of metals. Three relatively simple crystal structures are found for
most of the common metals: face-centered cubic, body-centered cubic, and hexagonal
close-packed.
Table 7.1 Atomic Radii and Crystal Structure for 16 Metals
AtoAto
mic mic
CrystRadius
b
CrysRadius
b

al (ntal (nm
Metal Structure
a
m) Metal Structure )
Aluminum FCC 0.1431 Molybdenum BCC 0.1363
Cadmium HCP 0.1490 Nickel FCC 0.1246
Chromium BCC 0.1249 Platinum FCC 0.1387
Cobalt HCP 0.1253 Silver FCC 0.1445
Copper FCC 0.1278 Tantalum BCC 0.1430
Gold FCC 0.1442 Titanium(α) HCP 0.1445
Iron BCC 0.1241 Tungsten BCC 0.1371
Lead FCC 0.1750 Zinc HCP 0.1332
The Face-centered Cubic Crystal Structure
The crystal structure found for many metals has a unit cell of cubic geometry, with atoms
located at each of the corners and the centers of all the cube faces. It is aptly called the
face-centered cubic (FCC) crystal structure. Some of the familiar metals having this crystal
structure are copper, aluminum, silver, and gold. Figure 7.1a shows a hard sphere model for the
FCC unit cell, whereas in Figure 7.1b the atom centers are represented by small circles to
provide a better perspective of atom positions. The aggregate of atoms in Figure 7.1c
represents a section of crystal consisting of many FCC unit cells. These spheres or ion cores
touch one another across a face diagonal; the cube edge length a and the atomic radius R are
related through











aptly adv. 适当地
适宜地
face-centered cubic 面心立方


diagonal dainl n.对角






equivalentikwivlnt
等同的，相等的

a2R2

For the FCC crystal structure, each corner atom is shared among eight unit cells, whereas
a face-centered atom belongs to only two. Therefore, one eighth of each of the eight corner
atoms and one half of each of the six face atoms, or a total of four whole atoms, may be
assigned to a given unit cell. This is depicted in Figure 7.1a, where only sphere portions are
represented within the confines of the cube. The cell comprises the volume of the cube, which
is generated from the centers of the corner atoms as shown in the figure.
coordination number 配位数
atomic packing factor 致密度





Corner and face positions are really equivalent; that is, translation of the cube corner
from an original corner atom to the center of a face atom will not alter the cell structure.
Two other important characteristics of a crystal structure are the coordination number
and the atomic packing factor (APF). For metals, each atom has the same number of
nearest-neighbor or touching atoms, which is the coordination number. For face-centered
cubic, the coordination number is 12. This may be confirmed by examination of Figure 7.1a;
the front face atom has four corner nearest-neighbor atoms surrounding it, four face atoms that
are in contact from behind, and four other equivalent face atoms residing in the next unit cell to
the front, which is not shown.
The APF is the fraction of solid sphere volume in a unit cell, assuming the atomic hard
sphere model, or





body-centered cubic 体心立方




volumeofatomsinaunitcell
APF

totalunitcellvolume
For the FCC structure, the atomic packing factor is 0.74, which is the maximum packing
possible for spheres all having the same diameter. Computation of this APF is also included as
an example problem. Metals typically have relatively large atomic packing factors to maximize
the shielding provided by the free electron cloud
chromium krumjmn.
tungsten tstnn. 钨








The Body- centered Cubic Crystal Structure
Another common metallic crystal structure also has a cubic unit cell with atoms located at
all eight corners and a single atom at the cube center. This is called a body-centered cubic
(BCC) crystal structure. A collection of spheres depicting this crystal structure is shown in

Figure 7.2c, whereas Figures 7.2a and 7.2b are diagrams of BCC unit cells with the atoms
represented by hard sphere and reduced-sphere models, respectively. Center and corner atoms
touch one another along cube diagonals, and unit cell length a and atomic radius R are related
through
4R

a

3
Chromium, iron, tungsten, as well as several other metals listed in Table 7.1 exhibit a
BCC structure.
Two atoms are associated with each BCC unit cell: the equivalent of one atom from the
eight corners, each of which is shared among eight unit cells, and the single center atom, which
is wholly contained within its cell. In addition, corner and center atom positions are equivalent.
The coordination number for the BCC crystal structure is 8; each center atom has as nearest
neighbors its eight corner atoms. Since the coordination number is less for BCC than FCC, so
also is the atomic packing factor for BCC lower—0.68 versus 0.74.




hexagonal close-packed 密排
方


midplane midpleinn.中
平面





cadmium kdmimn. 镉
Figure

7.2 For the body-centered cubic crystal structure, (a) a hard sphere unit cell representation, (b) a
reduced-sphere unit cell, and (c) an aggregate of many atoms.
magnesium mni:zjm
镁

The Hexagonal Closed-packed Crystal Structure

Not all metals have unit cells with cubic symmetry, the final common metallic crystal
structure to be discussed has a unit cell that is hexagonal. Figure 7.3a shows a reduced-sphere
unit cell for this structure, which is termed hexagonal close-packed (HCP); an assemblage of
several HCP unit cells is presented in Figure 7.3b. The top and bottom faces of the unit cell
consist of six atoms that form regular hexagons and surround a single atom in the center.
Another plane that provides three additional atoms to the unit cell is situated between the top

and bottom planes. The atoms in this midplane have as nearest neighbors atoms in both of the
adjacent two planes. The equivalent of six atoms is contained in each unit cell; one- sixth of
each of the 12 top and bottom face corner atoms, one-half of each of the 2 center face atoms, diffracted difrktidvt.衍射
and all the 3 midplane interior atoms. If a and c represent, respectively, the short and long unit
cell dimensions of Figure 3.3a, the ca ratio should be 1.633; however, for some HCP metals
this ratio deviates from the ideal value.
The coordination number and the atomic packing factor for the HCP crystal structure are
the same as for FCC: 12 and 0.74, respectively. The HCP metals include cadmium,
magnesium, titanium, and zinc; some of these are listed in Table 7.1.

Figure

7.3 For the hexagonal close-packed crystal structure, (a) a reduced-sphere unit cell (a and c
represent the short and long edge lengths, respectively), and (b) an aggregate of many atoms.
The descriptions above were made using optical techniques, especially optical
microscopy. However, the absolute arrangement of the atoms in a crystal cannot be determined
in this way. This limitation was overcome in the early years of the 20th century, when it was
discovered that X-rays were scattered, or diffracted, by crystals in a way that could be
interpreted to yield the absolute arrangement of the atoms in a crystal, the crystal structure.
X-ray diffraction remains the most widespread technique used for structure determination, but
diffraction of electrons and neutrons is also of great importance, as these reveal features that
are complementary to those observed with X-rays.
The physics of diffraction by crystals has been worked out in detail. It is found that the
incident radiation is scattered in a characteristic way, called a diffraction pattern. The
positions and intensities of the diffracted beams are a function of the arrangements of the atoms
in space and some other atomic properties, such as the atomic number of the atoms. Thus, if the

incident radiation入射辐射
diffraction pattern衍射图

positions and the intensities of the diffracted beams are recorded, it is possible to deduce the
arrangement of the atoms in the crystal and their chemical nature.
Reference: William ter, Fundamentals of Materials Science and Engineering,
Press:Chemical Industry Press, China, 2002,30-68.



Notes
1.A crystalline material is one in which the atoms are situated in a repeating or periodic array over
large atomic distances; that is, long-range order exists, such that upon solidification, the atoms
will position themselves in a repetitive three-dimensional pattern, in which each atom is bonded to
its nearest-neighbor atoms.
晶体材料 是指原子在较大范围内按一定规律周期性重复排列。换句话说，晶体一旦凝固
后存在长程有序，原子在重 复性三维空间点阵的位置被固定，每一个原子和其最近邻原子成
键。
is an extremely large number of different crystal structures all having long range atomic
order; these vary from relatively simple structures for metals, to exceedingly complex ones, as
displayed by some of the ceramic and polymeric materials.
有相当多的晶体结构也是长程有序的，但他们既不同于金属的简单结构，也不同 于陶瓷
和聚合物材料非常复杂的结构。
A unit cell is chosen to represent the symmetry of the crystal structure, wherein all the atom
positions in the crystal may be generated by translations of the unit cell integral distances along
each of its edges. Thus, the unit cell is the basic structural unit or building block of the crystal
structure and defines the crystal structure by virtue of its geometry and the atom positions within.
晶胞用来表示 晶体结构的对称性。晶体中所有原子的位置可由沿晶胞每个边的距离矢量
来表示。因此晶胞是晶体最基本 的结构单元，通过几何格架和内部原子位置的定义了晶
体结构。
3．For the FCC crystal structure, each corner atom is shared among eight unit cells, whereas a

face- centered atom belongs to only two. Therefore, one eighth of each of the eight corner atoms
and one half of each of the six face atoms, or a total of four whole atoms, may be assigned to a
given unit cell.
在面心立方晶体结构中，每一顶角原子为八个晶胞共有， 而位于面心上的原子属于两个
相邻晶胞。因此八个顶角原子中每个原子的八分之一和六个晶面上每个原子 的二分之一，共
计四个原子属于这个晶胞。
4. The positions and intensities of the diffracted beams are a function of the arrangements of the
atoms in space and some other atomic properties, such as the atomic number of the atoms. Thus, if
the positions and the intensities of the diffracted beams are recorded, it is possible to deduce the
arrangement of the atoms in the crystal and their chemical nature.
衍射束的位置与强度是原子的空间排列和原子序数等 性质的函数。因此如果纪录衍射束
的强度和位置，就可以推算出原子在晶体中的排列和它们的化学特性。


Exercises
1. Choose correct choice for each question according to the text
（1）A lattice is:
(a) A crystal structure
(b) An ordered array of points
IA unit cell
（2）The coordination number of the face- centered cubic crystal structure is:
(a) 8
(b) 4
I 12

（3）The
atomic packing factor of body-centered cubic crystal structure is:
(a) 0.68
(b) 0.74
I 0.58

2. Translate the following into Chinese
Two atoms are associated with each BCC unit cell: the equivalent of one atom from the eight
corners, each of which is shared among eight unit cells, and the single center atom, which is

wholly contained within its cell. In addition, corner and center atom positions are equivalent.
ate the following into English
大部分金属元素具有面心立方、体心立方和密排六方三种致密晶体结构之一 ，其中面心立
方和密排六方结构等径刚球最有效的堆积方式，致密度相同且最大为0.74。因此这些致 密的
晶体结构处于能量最低，最稳定的状态。




Supplementary Reading
Amorphous Metals
Some materials are called amorphous无定形的or noncrystalline非结晶的because they
lack long-range order in their atomic structure. It should be noted that in general materials have a
tendency to achieve a crystalline state because that is the most stable state and corresponds to the
lowest energy level. However, atoms in amorphous materials are bonded in a disordered manner
because of factors that inhibit the formation of a periodic arrangement. Atoms in amorphous
materials, therefore, occupy random spatial position as opposed to specific position in crystalline
solids.
An amorphous condition may be illustrated by comparison of the crystalline and
noncrystalline structures of the ceramic compound silicon dioxide (SiO
2
), which may exist in both
states. The best known amorphous material is window glass and hence amorphous materials are
often referred to as glasses.
Whether a crystalline or amorphous solid form depends on the ease with which a random
atomic structure in the liquid can transform to an ordered state during solidification. Amorphous
materials, therefore, are characterized by atomic or molecular structures that are relatively
complex and become ordered only with some difficulty. Furthermore, rapidly cooling through the
freezing temperature favors the formation of a noncrystalline solid, since little time is allowed for
the ordering process.

Metals are usually able to crystallize even at very high cooling rates, but under extreme
conditions metallic glasses can be produced in some alloys. Metallic glasses are not transparent.
Nonetheless, the lack of a long range structure in metallic glasses does produce some unusual
properties and these are employed in specialist applications. For example, alloys such as
78%Fe-9%Si-13%B that contain a high percentage of semimetals半金属, Si and B, may form
metallic glasses through rapid solidification at cooling rates in excess of 10
8
℃s. At such high
cooling rates, the atoms simply do not have enough time to form a crystalline structure and instead
form a metal with an amorphous structure, that is, they are highly disordered. In theory, any
crystalline material can form a noncrystalline structure if solidified rapidly enough form a molten
state.
Perhaps the most important current application of amorphous metals is in read-write compact
discs (CD-RW). All compact discs (CDs) depend on changing the extent to which the disc reflects
light from a laser to store information (e.g. music or computer data). Conventional CDs control
reflection using small pits that are produced mechanically in a factory and so standard CDs are
read-only. In contrast, recordable CDs(CD-R) discs contain a dye layer within the disc. This dye
undergoes a color change when heated. CD-R discs store information by using a laser to heat a
small region of the CD, producing a localized color change that, in turn modifies the reflectivity of
the disc. Hence the term “burning a CD”. CD-R discs are very cheap to produce, but suffer from
the disadvantage that the color change is permanent, so that the disc is write-once-read-many
(WORM). Thus, a single mistake when burning the CD and the result is only fit for use as a
coaster.
CD-RW discs work in a different fashion. Within the disc is a metallic layer melts. When this
is heated locally by a laser, at a fairly highly power, a small region of the metallic layer melts. The
rest of the disc makes an efficient heat sink and so the small molten region cools extremely
quickly and is unable to crystallize. The resulting amorphous region reflects light differently from
its crystalline surroundings and so can do the same job as the pits in a conventional CD. The key
different is that, if the amorphous region is reheated, but with a lower laser power than before, the
amorphous region becomes hot enough to allow crystalline to take place, but not so hot that the
region re- melts. This erases the original information, making the CD-RW disc re-writable.
Amorphous materials, because of their structure, possess properties that are superior. For

instance, metallic glasses possess higher strength, better corrosion characteristics, and magnetic
properties when compared to their crystalline counterparts. Finally, it is important to note that
amorphous materials do not show sharp diffraction patterns when analyzed using x-ray diffraction
techniques. This is due to a lack of order and periodicity in the atomic structure.

Part Ⅱ METALLIC MATERLALS AND
ALLOYS

Unit 8

Text

Metal-Matrix Composites




Generality

As the name implies, for metal-matrix composites (MMCs),

the matrix is a ductile metal. These materials may be utilized at
ductile metal，延性金属
higher service temperatures than their base metal counterparts;

furthermore, the reinforcement may improve specific stiffness,

specific strength, abrasion resistance, creep resistance, thermal
superalloysju:pəælɔi
conductivity, and dimensional stability. The superalloys, as well as
n.高温合金
alloys of aluminum, magnesium, titanium, and copper, are employed

as matrix materials. The reinforcement may be in the form of

particulates, both continuous and discontinuous fibers, and whiskers;
cermet
concentrations normally range between 10 and 60 vol%. In a sense,
n.金属陶瓷
the cermets fall within this MMC scheme.

Generally MMCs are classified according to type of used

reinforcement and the geometric characteristics of the same (see in

Fig.1). In particular, the main classification groups these composites
filament 细丝
into two basic categories:
whisker 晶须
• continuous reinforcement composites, constituted by

continuous fibers or filaments;

• discontinuous reinforced composites, containing short fibers,

whiskers or particles.
The choice of reinforcement is related to the type of
application, to the compatibility between the reinforcement and the
matrix and to the interfacial resistance matrix reinforcement. As
already mentioned, the ceramic reinforcement is usually in the form
of oxides, carbides and nitrides, i.e. that elements with high strength
and stiffness both at room temperature and at high temperatures. The
common reinforcing elements are silicon carbide (SiC), alumina
(Al
2
O
3
), titanium boride (TiB
2
), boron and graphite. That particle
type is the reinforcement most common and economical. mechanical strength，
The continuous reinforcement composites have the possibility 机械强度
to incorporate a mix of properties in the chosen material as the
matrix, as better wear resistance, lower coefficient of thermal
expansion and higher thermal conductivity. The products are also
characterized by high mechanical strength (especially fatigue ductility 塑
strength) along the direction of reinforcement, so they are highly
anisotropic.
Discontinuous reinforcement has a positive effect on properties extrusion
as hardness, wear resistance, fatigue resistance, dimensional stability
挤压,挤出
and compression resistance. This latter materials also show a forging锻造
significant increase in stiffness but to the disadvantage of ductility
and fracture toughness. One of the biggest advantages of
discontinuously reinforced composites is the possibility (especially
in the case of reinforced aluminium alloy) to work with the usual
techniques of rolling, extrusion and forging. The addition of the hard
second phase however entails a fast tool wear, requiring sometimes
diamond tools.

intermetallic
adj.金属间(化合)的

Fig.1 Schematic illustration of the reinforcement type about MMC:
n. Long unidirectional fiber; b) Short fiber and whiskers;
c) Particle
The matrix was considered for a long time simply a means to
hold together the fibers or any other type of reinforcement: however
this speech especially for a polymer matrix composite is effective.
Over the years instead it has been increasingly clear that the
microstructure of the matrix and consequently its mechanical
properties, exerts a considerable influence on the overall composite
performance. Among the most metal alloys used as a matrix in
MMC, there are aluminium, titanium, magnesium and copper, with
intermetallic compounds that are finding growing interest due to
their excellent resistance at high temperature. The main
combinations of MMC systems can be summarized as follows:
• Alluminium
- Long fiber: boron, silicon carbide, alumina, graphite
- Short fiber: alumina, alumina-silicon
- Whiskers: silicon carbide
- Particle: silicon carbide, boron carbide
• Magnesium
- Long fiber: alumina, graphite
- Whiskers: silicon carbide
- Particle: silicon carbide, boron carbide
• Titanium


















tungsten 






钨

- Long fiber: silicon carbide
- Particle: titanium carbide
• Copper
- Long fiber: silicon carbide, graphite
- Particle: titanium carbide, silicon carbide, boron carbide
- Filament: niobium – titanium
• Superalloys
o. Filament: tungsten








Both reinforcement and matrix are also selected on the basis of
what will be the interface that unites them. In fact, cause to the
fabrication and working conditions to which these materials are
submitted, along the interface fibermatrix special processes
develop, capable in this zone of producing compounds andor phases
that can significantly influence the mechanical properties of the
composite. This interface can be as a simple zone of chemical bonds
(as the interface between the pure aluminium and alumina), but can
also occur as a layer composed by reaction matrixreinforcement
products (type carbides produced between light alloy and carbon
fibers) or as a real reinforcement coatings (for example, the C
coating between SiC fibers and titanium matrix).
The mechanical and thermal MMC properties can be
summarized by a quantitative way through the following table:
Table 1 Main mechanical properties for MMCs
Mechanical properties
Density ρ
Modulus of elasticity E
Specific resistance Eρ
Tensile Strength, Ultimate σ
r
Reference data
2.5 – 3.1 gcm
3

90-300 Mpa
30-60
300-700 Mpa

Thermal conductivity C
C.T.E.
120-200 WmK
7-20 μmK


In particular, note the fact that the Eρ value for conventional

metals usually is not more than 25.

Fig.2 Graphic comparison of the specific stiffness (Eρ) of
conventional metal and MMC
About the possible disadvantages for the MMC production and
application , these are based, comparing it to metals and polymer
matrix composites, mainly on the following points:
- Expensive production system
- Technology still comparatively immature
- Complexity about the production processes (especially about
the long fiber MMC )
- Limited experience of services dedicated to production
By this observation it is clear as major problems for the
application of this technology are mainly related to the fact that,
despite the first studies date back to the fifties, is still in the early
development stages about many ways.
Production and Processing of Metal
Matrix Composites
















precursor 
n.前体，初期形式
prototypeprəutətaip原型
reforming procedures，
重整过程

metallurgical
adj.冶金的
infiltration
n.浸渗
squeeze casting，模压铸造
perform，初加工的成品

Metal matrix composite materials can be produced by many
different techniques. The focus of the selection of suitable process pressing n冲压模压
engineering is the desired kind, quantity and distribution of the sinteringn烧结
reinforcement components (particles and fibers), the matrix alloy
and the application. By altering the manufacturing method, the
processing and the finishing, as well as by the form of the hot isostatic pressing，
reinforcement components it is possible to obtain different
characteristic profiles, although the same composition and amounts
of the components are involved. The production of a suitable
precursor material, the processing to a construction unit or a
semi-finished material (profile) and the finishing treatment must be
separated. For cost effective reasons prototypes, with dimensions
close to the final product, and reforming procedures are used, which
can minimize the mechanical finishing of the construction units.
In general the following product engineering types are possible:
• Melting metallurgical processes
p. infiltration of short fiber-, particle- or hybrid preforms
by squeeze casting, vacuum infiltration or pressure
infiltration
q. reaction infiltration of fiber- or particle preforms
r. processing of precursor material by stirring the
particles in metallic melts, followed by sand casting,
permanent mold casting or high pressure die casting
• Powder metallurgical processes
s. pressing and sintering andor forging of powder
mixtures and composite powders
t. extrusion or forging of metal-powder particle mixtures
u. extrusion or forging of spraying compatible precursor
materials
• Hot isostatic pressing of powder mixtures and fiber clutches
热等静压
thixo casting，触融压铸

weldingn.焊接











agglomerate 
n.附聚物, 凝聚物
porosityn. 孔隙度

• Further processing of precursor material from the melting

metallurgy by thixo casting or –forming, extrusion, forging, cold
massive forming or super plastic forming
• Joining and welding of semi-manufactured products
• Finishing by machining techniques
• Combined deformation of metal wires



(group

superconductors).
Melting metallurgy for the production of MMCs is at present of
greater technical importance than powder metallurgy. It is more
economical and has the advantage of being able to use well proven
casting processes for the production of MMCs. For melting
metallurgical processing of composite materials three procedures
are mainly used:
• compo-casting or melt stirring
• gas pressure infiltration
• squeeze casting or pressure casting.
Both the terms compo-casting and melt stirring are used for
stirring particles into a light alloy melt. The particles are often tend
to form agglomerates, which can be only dissolved by intense
stirring. However, here gas access into the melt must be absolutely
avoided, since this could lead to unwanted porosities or reactions.
Careful attention must be paid to the dispersion of the reinforcement
components, so that the reactivity of the components used is
coordinated with the temperature of the melt and the duration of
stirring, since reactions with the melt can lead to the dissolution of
the reinforcement components. Because of the lower surface to
volume ratio of spherical particles, reactivity is usually less critical
with stirred particle reinforcement than with fibers. The melt can be
cast directly or processed with alternative procedures such as
squeeze casting or thixo casting.


wettability 
n. 浸润性
molten 
adj. 熔化的，熔融的





mold filling，充型
die-cast，压铸
squeeze-cast，模压铸造
inclusion  n.夹







residuen.残留

In gas pressure infiltration the melt infiltrates the preform with
a gas applied from the outside. A gas that is inert with respect to the turbulence
matrix is used. The melting of the matrix and the infiltration take n. 湍流,涡流
place in a suitable pressure vessel. There are two procedure variants
of gas pressure infiltration: in the first variant the warmed up
preform is dipped into the melt and then the gas pressure is applied
to the surface of the melt, leading to infiltration. The infiltration
pressure can thereby be coordinated with the wettability of the
preforms, which depends, among other things, on the volume
percentage of the reinforcement. The second variant of the gas
pressure infiltration procedure reverses the order: the molten bath is
pressed to the preform by the applied gas pressure using a standpipe
and thereupon infiltrates the bath. In gas pressure infiltration the
response times are clearly longer than in squeeze casting, so that the
materials must be carefully selected and coordinated, in order to be
able to produce the appropriate composite material for the
appropriate requirements.
Squeeze casting or pressure casting are the most common
manufacturing variants for MMCs. After a slow mold filling the melt
solidifies under very high pressure, which leads to a fine-grained
structure. In comparison with die-casted parts the squeeze-casted
parts do not contain gas inclusions, which permits thermal treatment
of the produced parts. With direct squeeze casting the pressure for
the infiltration of the prefabricated preforms is applied directly to the
melt. The die is thereby part of the mold, which simplifies the
structure of the tools substantially. However, with the direct
procedure there is a disadvantage in that the volume of the melt must
be determined exactly, since no gate is present and thus the quantity
of the melt determines the size of the cast construction unit. A
further disadvantage is the appearance of oxidation products, formed

in the cast part during dosage. In contrast, in indirect squeeze
casting, where the melt is pressed into the form via a gate system,
the residues will remain in this gate. The flow rate of the melt
through a gate is, due to its larger diameter, substantially less than
with die casting, which results in a less turbulent mold filling and
gas admission to the melt by turbulences is avoided.
Both pressure casting processes make the production of
composite materials possible, as prefabricated fiber or particle
preforms are infiltrated with melt and solidify under pressure. A
two- stage process is often used. In the first stage the melt is pressed
into the form at low pressure and then at high pressure for the
solidification phase. This prevents damage to the preform by too fast
infiltration. The squeeze casting permits the use of relatively reactive
materials, since the duration of the infiltration and thus the response
time, are relatively short. A further advantage is the possibility to
manufacture difficultly shaped construction units and to provide
partial reinforcement, to strengthen those areas which are exposed to
a higher stress during service.
Reference:
[1] Riccardo Donnini, Metal Matrix Composite: Structure and Technologies [D] Rome:
University of Rome “Tor Vergata”, 2008
[2] Karl U. Kainer,

Metal Matrix Composites. Custom-made Materials for Automotive and
Aerospace Engineering [M] WILEY-VCH Verlag GmbH & Co. KgaA, Weinheim,
2006:7-12
[3] William ter,Jr., Fundamentals of Materials Science and Engineering [M]New
York:John Wiley & Sons, Inc,2001:s158

Notes
materials may be utilized at higher service temperatures than their base metal counterparts;
furthermore, the reinforcement may improve specific stiffness, specific strength, abrasion
resistance, creep resistance, thermal conductivity, and dimensional stability.
与对应基底 金属相比，金属基复合材料可被利用在较高的工作温度下，而且增强相可以
提高金属基复合材料的单位刚 度，单位强度，抗磨强度，蠕变阻力，热导率以及尺寸稳定性。
fact, cause to the fabrication and working conditions to which these materials are submitted,
along the interface fibermatrix special processes develop, capable in this zone of producing
compounds andor phases that can significantly influence the mechanical properties of the
composite.
事实 上，由于金属基复合材料的制备和工作条件的原因，沿着纤维基体相界面出现了
特殊物理过程，在界面区 域能生产明显影响金属基复合材料的化合物和或物相。
matrix composite materials can be produced by many different techniques. The focus of
the selection of suitable process engineering is the desired kind, quantity and distribution of the
reinforcement components (particles and fibers), the matrix alloy and the application.
金属基复合材料的制备可采取许多不同工艺 。重点是选择合适的工艺过程达到金属基
复合材料预期的种类，理想的增强相含量和成分配比（颗粒和纤 维），预期的基体合金和用
途。
cost effective reasons prototypes, with dimensions close to the final product, and reforming
procedures are used, which can minimize the mechanical finishing of the construction units.
考虑产品成本效益的原因，采用接近最终成品尺寸的模型和 加工重整过程，最小化结构
单元的机械加工工艺。
l attention must be paid to the dispersion of the reinforcement components, so that the
reactivity of the components used is coordinated with the temperature of the melt and the duration
of stirring, since reactions with the melt can lead to the dissolution of the reinforcement
components.
由于熔体间的反应可引起增强相组元溶解，因此必须关注增强相组元 的分散性，以便增
强相组元的活性与熔体温度和搅拌时间相协调。
gas pressure infiltration the response times are clearly longer than in squeeze casting, so that

the materials must be carefully selected and coordinated, in order to be able to produce the
appropriate composite material for the appropriate requirements.
真空压力浸渗法的反应时间比挤压铸 造法的反应时间长，为了能够制备出恰当组分、适
合需要的复合材料，原料必须经过仔细选择和调配。< br>

Exercises
1. Choose correct choice for each question according to the text
(1)In a material composite, when the matrix is a metal or an its alloy, we have a

(a) Metal-Matrix Composite; (b) Polymer–Matrix Composite;
(c) Ceramic-matrix Composite; (c) Carbon-Carbon Composite.
(2)The reinforcement type about metal-matrix composites does not include
(a) long unidirectional fiber; (b) short fiber and whiskers;
(c) particle; (d ) cermets.
(3)Metal matrix composite materials can be produced by technique.

(a) gas pressure infiltration; (b) compo-casting or melt stirring;
(c) melting metallurgy; (d) squeeze casting or pressure casting.

2. Translate the following into English
真空 压力浸渗法有两个变化过程：第一个变化过程是膨胀的预成型成品浸渍到熔体，随
着熔体表面的气压的加 载，形成浸渗。

3. Translate the following into Chinese
The addition of the hard second phase however entails a fast tool wear, requiring sometimes
diamond tools.

Supplementary Reading
Industrial applications of Metal-Matrix Composites
Considered experimental materials, metal matrix composites are a good alternative to
traditional materials, due to their hardness, specific strength and creep resistance. Despite this

interest, they regards still niche applications, about the industrial world, cause to their cost does
not allow a wider use. Major applications are in the aerospace and aeronautical field, where the
material costs are not so limited and where it is researched continuous improvement about the
specific performance. The fact remains that an ever greater interest are taking MMC applications
regarding the automotive areas, with particular attention to the fields of engine and brake systems.
The special properties of these materials, particularly their ability to change them depending on
the technology adoption process, has enlarged its application field to other interesting areas as
sports (where duration and resistance are required during performance of mechanical components )
to ultimately get to the electronic applications, where the thermal properties and the right value of
C.T.E. are essential.
Aeronautics
Initially (in the early 70’s) the attention was focused on increasing the creep resistance of the
rotor blades through the reinforcement of aluminium alloys by boron fibers, but the tolerance to
the presence of foreign objects was low. Recently, interest has shifted to asymmetric components
for aircraft engines, many of which are ideally equipped with unidirectional high- performance,
properties that are especially exploited in titanium matrix composites.
Automotive

By lower production costs and by the attraction about savings in weight the MMC application
has increased more and more about the car field and not only about the competition. This is due to
the major properties at high working temperature, that have made the material composite an
interesting alternative to traditional materials. In fact there is an increasingly important MMC
presence about engines (engine block and pistons), drive shaft and disc brakes (including rail type).
For example for the brake systems, the MMC application concerns especially the discs that are
produced by aluminium matrix reinforced by SiC particle.
For this reason, in October 1991, Ford and Toyota decided to adopt disks made by Al-80%,
SiC-20%. The choice of a 20% SiC was made to combine a good surface resistance (increased by
SiC) with a thermal and mechanical stability during the work. The matrix is also aged to prevent
the property degradations during use. After that use other manufacturers have adopted these
material types, companies as: Volkswaghen, Toyota with the RAV4EV, the Plymouth Prowler, GM
EV-1, Precept, Impact, Ford Prodigy, Lotus with Elise.

Electronics
New generation advanced integrated circuits are generating more heat then previous types.
Therefore, the dissipation of heat becomes a major concern. Indeed, thermal fatigue may occur
due to a small mismatch of the coefficient of thermal expansion between the silicon substrate and
the heat sink (normally molybdenum). This problem can be solved by using MMCs with exactly
matching coefficients (e.g. Al with boron or graphite fibres and Al with SiC particles).
Besides a low coefficient of thermal expansion and a high thermal conductivity, these
Al-based MMCs also have a low density and a high elastic modulus. Hermetic package materials
are developed to protect electronic circuits from moisture and other environmental hazards. These
packages have often glass-to- metal seals. Therefore, materials with an
thermal expansion are required. Al-based

MMCs are fulfilling this condition, as the coefficient of
thermal expansion is depending upon the volume fraction of the fibres or particles.
Manufacturing
The manufacturing operations of the third level performed on an MMC (for instance, those
relating to the cutting and welding operation) are a very refined and important, cause to the
particular material shape, making it highly abrasive to the tool during chip machining, and
difficult to weld, cause to the not homogeneity in the welded area.
The cutting operations (conventional cutting, turning, milling and grinding) are commonly
applied to MMC, but often the problem regards the tool coating.
In general, many problems become significant with the increase in the reinforcement
percentage and its greatness, as tool goes to meet the harder material, producing more stress on the
same tool.
Reference:
[1] Riccardo Donnini, Metal Matrix Composite: Structure and Technologies [D] Rome: University of Rome “Tor Vergata”, 2008

Part Ⅲ Ceramics


Unit 9 Introduction to Ceramics
Text

Introduction to Ceramics
The word ceramic, derives its name from the Greek word keramos, meaning


which in turn is originated from an older Sanskrit root, meaning
burn
word was used to refer to a product obtained through the action of fire upon earthy
materials. Since, in ancient times, the potter was significantly associated with clay
work, as such ceramics meant art of potter dealing with clay and clay article fired to
give hardness.
①
In other words, ceramics basically means an art of making articles
of clay and firing them to produce stone like products.
Ceramics make up one of three large classes of solid materials. The other
material classes include metals and polymers. Ceramics can be defined as inorganic,
non-metallic materials that are typically produced using clays and other minerals
from the earth or chemically processed powders. Ceramics are typically crystalline
in nature and are compounds formed between metallic and non-metallic elements
such as aluminium and oxygen (alumina-Al
2
O
3
), silicon and nitrogen (silicon
nitride- Si
3
N
4
)，and silicon and carbon (silicon carbide-SiC).
Most people, when they hear the word ceramics, think of art, dinnerware,
pottery, tiles, brick and toilets. The above mentioned products are commonly
referred to as traditional or silicate-based ceramics. While these traditional products
have been, and continue to be, important to society, a new class of ceramics has
emerged that most people are unaware of. Ceramics comprise a wide variety of
materials which constitute a major industry. The principal facets of the ceramic
industry, in order of increasing value of annual production, are (1) abrasives; (2)
porcelain enamel coating; (3) refractories; (4) whitewares; (5) structural clay
products; (6) electronic and technical ceramic products; and (7) glass.

②

Glass
accounts for about 45% of all ceramics produced.
The essential raw material of ceramics is clay. This inexpensive ingredient,
found naturally in great abundance, often is used as mined without any upgrading of
quality. Clay is essentially a hydrated compound of aluminum and silicon
H
2
Al
2
Si
2
O
9
,

containing more or less foreign matter such as (1) ferric oxide Fe
2
O
3
,
which contributes the reddish color frequently associated with clay; (2) silica SiO
2

as sand; and (3) calcium carbonate CaCO
3
as limestone etc.
③
Since clay is formed
by the decomposition of igneous rocks followed by transportation of the fine
particles by running water and later deposition of these particles by sedimentation
when the flow of water diminishes in speed, the quality of clays shows a wide
range.
④
Another reason for clay’s popularity lies in the ease with which clay
products may be formed; when mixed in the proper proportions, clay and water
[] adj.梵语
的







[]
adj. 无机的












[
] n. 搪瓷
[] n.
耐火材料
[] n. 卫生瓷






[] n. 火成岩

form a plastic mass that is very amenable to shaping. The shape is retained on
drying, and subsequent heating produces a coherent, hard mass, which suffers in the
process more or less shrinkage and deformation depending upon the composition of
the raw materials, and the method and temperature of treatment. Common bricks are
made of crude materials without careful regulation of the conditions of treatment.
Bricks and plain clay products possess an earthy surface and fracture, and the
strength depends upon the materials and treatment. Porcelain, on the other hand,
possesses a glasslike or vitreous surface and fracture, and is not porous. Porcelain is
made by mixing the clay with some powdered feldspar mineral, potassium








[] adj. 天然的
aluminosilicate (KAlSi
3
O
8
approximately). At the temperature of firing, feldspar
undergoes a gradual change from the crystalline to the glassy state, and the rate
depending upon the time of heating and the temperature to which it is subjected.
The fusion point of feldspar is of the order of 1300℃, whereas that of kaolin (pure
clay) is of the order of 1700℃. Subjection of the porcelain raw material to the latter
temperature would result in the formation of a glass. But when the temperature used
is below the melting point of the clay portion and about the melting point of the
feldspar, the latter produces a glass cement which binds together the particles of the
former. When ground quartz SiO
2
is added to the original clay mixture, the
shrinkage of the material in the processes of drying and firing is reduced, the
resistance to deformation during firing is increased, and the temperature coefficient
of expansion of the product is affected.
The range of clay, feldspar and quartz, as to the ratios in the mixture and as to
individual composition of each, as well as the available range of temperature of
firing makes possible the production of products of a wide variety of physical
structure.
⑤
There has been proposed an arbitrary line of demarcation, namely that the
unglazed product, such as has been described, which absorbs not more than 1% of
its weight upon and after immersion in water, shall be termed porcelain, otherwise it
shall be called earthenware. Such a nonporous material as porcelain, which includes
chinaware, is also distinctly translucent in thicknesses of a few millimeters, whereas
earthenware is nontranslucent and somewhat porous.
Ceramics have been in use for all of man’s history. Clay baked in a fire
exhibited properties of strength and the ability to hold water, and pottery is an
important object studied in archeological sites because it tells a great deal about the
technology of the culture that created it. Ceramics are used in the very highest
technology applications (superconductors, tiles for the space shuttle (The ceramic
tiles used on the Space Shuttle are extreme examples of the poor thermal
conductivity of ceramics.), etc.) and some of the lowest (building bricks).
Since ancient times, the technology and applications of ceramics (including
glass) has steadily increased. We often take for granted the major role that ceramics
have played in the progress of humankind. Lets us look at a few examples of the
importance of ceramics in our lives.
Modern iron and steel and non-ferrous metal production would not be possible
without the use of sophisticated refractory materials that are used to line high
temperature furnaces, troughs and ladles. Metals make automobiles, machinery,


[❖] adj. 玻璃
质的
[] n. [矿]
长石










热膨胀系数







[] n. 陶器

planes, buildings, and thousands of other useful things possible. Refractory ceramics
are enabling materials for other industries as well. The chemical, petroleum, energy
conversion, glass and other ceramic industries all rely on refractory materials.
Much of the construction industry depends on the use of ceramic materials.
This includes brick, cement, tile, and glass. Cement is used to make concrete which
in turn is used for roadways, dams, buildings, and bridges. Uses of glass in the
construction industry include various types of windows, glass block, and fibers for
use in insulation, ceiling panels and roofing tiles. Brick is used for homes and
commercial buildings because of its strength, durability, and beauty. Brick is the



[]
adj. 尖端的
[] vt. 给…装（做）
内衬
[] n.熔炉
[] n.槽
only building product that will not burn, melt, dent, peel, warp, rot, rust or be eaten
by termites. Tile is used in applications such as flooring, walls, countertops, and
fireplaces. Tile is also a very durable and hygienic construction product that adds
beauty to any application.
An important invention that changed the lives of millions of people was the
incandescent light bulb. This important invention by Thomas Edison in 1879 would
not be possible without the use of glass. Glass’s properties of hardness,
transparency, and its ability to withstand high temperatures and hold a vacuum at
the same time made the light bulb a reality. The evolution of lighting technology
since this time has been characterized by the invention of increasingly brighter and
more efficient light sources. By the middle of twentieth century, methods of lighting
seemed well established-with filament and fluorescent lamps for interiors, neon
lamps for exterior advertising and signs, and sodium discharge lamps for streets.
Since this time, light-emitting diode (LED) technology has been developed with
applications in watches, instrument panel indicators, telecommunications (optical
fiber networks), data storage (CD technology), and document production (laser
printers).
The electronic industry would not exist without ceramics. Ceramics can be
excellent insulators, semiconductors, superconductors, and magnets. It's hard to
imagine not having mobile phones, computers, television, and other consumer
electronic products. Ceramic spark plugs, which are electrical insulators, have had a
large impact on society. They were first invented in 1860 to ignite fuel for internal
combustion engines and are still being used for this purpose today. Applications
include automobiles, boat engines, lawnmowers, and the like. High voltage
insulators make it possible to safely carry electricity to houses and businesses.
Ceramics also play an important role in addressing various environmental
needs. Ceramics help decrease pollution, capture toxic materials and encapsulate
nuclear waste. Today's catalytic converters in vehicles are made of cellular ceramics
and help convert noxious hydrocarbons and carbon monoxide gases into non-toxic
carbon dioxide and water. Advanced ceramic components are starting to be used in
diesel and automotive engines. Ceramics’ light weight and high- temperature and
wear resistant properties, result in more efficient combustion and significant fuel
savings. Ceramics are also used in oil spill containment booms that corral oil so it
can be towed away from ships, harbours, or offshore oil drilling rigs before being
burned off safely.
[] n. 桶，罐










[]
adj. 卫生的


[
]
白炽灯泡




[] n.日
光灯（管）
[] n.霓虹灯
n. 放电管




[
] n.半导体
[
] n.超导体
[ ] n. 火

Reference: Greg Geiger, Technical Information Manager, American
Ceramic Society. Introduction to Ceramics [EBOL].(2001-2-20). .

花塞




[]
vt. 封装

[] n. 一
氧化物
[] n.
二氧化物


[  ] n.
漏油栅
[] vt.把…聚
集在一起
n. 海上石油钻探平台

Notes
, in ancient times, the potter was significantly associated with clay work, as such ceramics
meant art of potter dealing with clay and clay article fired to give hardness.
因为在古代 制陶工人的工作与粘土加工关联性很大，因此陶瓷指的是加工粘土的制陶工
人生产的工艺品，以及经过烧 成而产生硬度的粘土制品。
principal facets of the ceramic industry, in order of increasing value of annual production,
are (1) abrasives; (2) porcelain enamel coating; (3) refractories; (4) whitewares; (5) structural clay
products; (6) electronic and technical ceramic products; and (7) glass.
按照年产值增加的顺序排列，陶瓷工业所包括的主要方面是：（1）研磨剂；（2）搪瓷涂
层；（3） 耐火材料；（4）卫生瓷；（5）结构性粘土产品；（6）电子陶瓷和技术陶瓷产品；（7）
玻璃。
is essentially a hydrated compound of aluminum and silicon H
2
Al
2
Si
2
O
9
,

containing more
or less foreign matter such as (1) ferric oxide Fe
2
O
3
, which contributes the reddish color
frequently associated with clay; (2) silica SiO
2
as sand; and (3) calcium carbonate CaCO
3
as
limestone etc.
粘土本质上是一种铝和硅的水合物H
2
Al
2
Si
2
O
9
，它或多或少地含有杂质，例如（1）氧化铁Fe
2
O
3
，它是粘土常常呈现微红色的原因；（2）以砂的形式存 在的氧化硅（SiO
2
）；
（3）以石灰石的形式存在的碳酸钙（CaCO
3
）。
clay is formed by the decomposition of igneous rocks followed by transportation of the
fine particles by running water and later deposition of these particles by sedimentation when the
flow of water diminishes in speed, the quality of clays shows a wide range.

粘土是由火成岩分解形成的，随后流水将火成岩分解产生的细颗粒冲走，随着水流速度
的减小，它们 再通过沉淀作用沉积下来，因此粘土的组成的变化范围很广。
range of clay, feldspar and quartz, as to the ratios in the mixture and as to individual
composition of each, as well as the available range of temperature of firing makes possible the
production of products of a wide variety of physical structure.
粘土、长石和石英在混合物中的比例，和它们各自的组成的 范围，以及可行的烧成温度
的范围，使得具有多种物理结构的产品的生产成为可能。

Exercises
1. Reading comprehensions
(1)Ceramics can be used in many applications, please give some examples.
(2)What kinds of materials are generally classified as ceramics?
(3)Please compare the differences between traditional ceramics and special ceramics.

2．Choose the best answer to each of the following questions
(1) Which one is not the essential element of clay
(a) silicon
(b) aluminum
(c) potassium
(2)When ground quartz SiO
2
is added to the original clay mixture, the shrinkage of the material in
the processes of drying and firing is
(a) not affected
(b) reduced
(c) increased
(3)Today's catalytic converters in vehicles are made of
(a) refractories
(b) ceramic films
(c) cellular ceramics

3．Translate the following into English
无机非金属材料；耐火材料；搪瓷；一氧化物；二氧化物；半导体；超导体；水泥

4．Translate the following into Chinese
① decomposition; temperature coefficient of expansion; porcelain; pottery; spark plug; offshore
oil drilling rig; tile; furnace; feldspar; quartz
② Such a nonporous material as porcelain, which includes chinaware, is also distinctly
translucent in thicknesses of a few millimeters, whereas earthenware is nontranslucent and
somewhat porous.
③ The fusion point of feldspar is of the order of 1300℃, whereas that of kaolin (pure clay) is of
the order of 1700℃. Subjection of the porcelain raw material to the latter temperature would result
in the formation of a glass.
④ Modern iron and steel and non-ferrous metal production would not be possible without the use
of sophisticated refractory materials that are used to line high temperature furnaces, troughs and

ladles.


Supplementary Reading
Types of Ceramics
The term ceramics refers to a broad range of materials including not only polycrystalline
materials, but also powdered materials, thin films and single crystals, and glassy inorganic
materials. Most ceramic materials fall into an application- classification scheme that includes the
following groups: glasses, structural clay products, whitewares, refractories, abrasives, cements,
and the newly developed advanced ceramics. Fig. 9.1 presents a taxonomy of these several types;
some discussion is devoted to each.

Fig. 9.1 Classification of ceramic materials on the basis of application
Glasses
The glasses are a familiar group of ceramics; containers, windows, lenses, and fiber glass
represent typical applications. They are noncrystalline silicates containing other oxides, notably
CaO, Na
2
O, K
2
O, Al
2
O
3
, which influence the glass properties. A typical soda-lime glass consists
of approximately 70wt% SiO
2
, the balance being mainly Na
2
O (soda) and CaO (lime). Possibly
the two prime assets of these materials are their optical transparency and the relative ease with
which they may be fabricated.
Glass-ceramics
Most inorganic glasses can be made to transform from a noncrystalline state to crystalline
one by the proper high-temperature heat treatment. This process is called devitrification, and the
product is a fine-grained polycrystalline material which is often called a glass-ceramic. A
nucleating agent (frequently titanium dioxide) must be added to induce the crystallization or
devitrification process. Desirable characteristics of glass-ceramics include a low coefficient of
thermal expansion, such that the glass-ceramic ware will not experience thermal shock; in addition,
relatively high mechanical strengths and thermal conductivities are achieved. Some glass-ceramics
may be made optically transparent; others are opaque. Possibly the most attractive attribute of this
class of materials is the ease with which they may be fabricated; conventional glass-forming
techniques may be used conveniently in the mass production of nearly pore-free ware.
Clay Products
One of the most widely used ceramic raw materials is clay. Most of the clay-based products
fall within two broad classifications: the structural clay products and the whitewares. Structural
clay products include building bricks, tiles, and sewer pipes- applications in which structural
integrity is important. The whiteware ceramics become white after the high-temperature firing.
Included in this group are porcelain, pottery, tableware, china, and plumbing fixtures (sanitary

ware). In addition to clay, many of these products also contain other ingredients, each of which
has some role to play in the processing and characteristics of the finished piece.
Refractories
Another important class of ceramics that are utilized in large tonnages is the refractory
ceramics. The salient properties of these materials include the capacity to withstand high
temperatures without melting or decomposing, and the capacity to remain unreactive and inert
when exposed to severe environments. In addition, the ability to provide thermal insulation is
often an important consideration. Refractory materials are marketed in a variety of forms, but
bricks are the most common. Typical applications include furnace linings for metal refining, glass
manufacturing, metallurgical heat treatment, and power generation.

Abrasives
Abrasive ceramics are used to wear, grind, or cut away other material, which necessarily is
softer. Therefore, the prime requisite for this group of materials is hardness or wear resistance; in
addition, a high degree of toughness is essential to ensure that the abrasive particles do not easily
fracture. Furthermore, high temperatures may be produced from abrasive frictional forces, so
some refractoriness is also desirable.
Diamonds, both natural and synthetic, are utilized as abrasives; however, they are relatively
expensive. The more common ceramic abrasives include silicon carbide, tungsten carbide (WC),
aluminum oxide (or corundum), and silica sand.
Cements
Several familiar ceramic materials are classified as inorganic cements: cement, plaster of
paris, and lime, which, as a group, are produced in extremely large quantities. The characteristic
feature of these materials is that when mixed with water, they form a paste that subsequently sets
and hardens. This trait is especially useful in that solid and rigid structures having just about any
shape may be expeditiously formed. Also, some of these materials act as a bonding phase that
chemically binds particulate aggregates into a single cohesive structure.
Advanced Ceramics
The term Advanced Ceramics is opposite in meaning to “Traditional” or “Classical” Ceramics.
Ceramics that are utilized in high-technology (or high-tech) applications are sometimes termed
advanced ceramics. By high technology we mean a device or product that operates or functions
using relatively intricate and sophisticated principles; examples include electronic equipment
(such as CD players, etc.), computers, fiber- optic systems, spacecraft, aircraft, and military
rocketry. These advanced ceramics are typically either traditional ceramics whose properties have
been enhanced or newly developed, high-performance ceramics. They are also classified into two
classes: functional ceramics and engineering ceramics.

Reference: William D. Callister, Jr. Fundamentals of Materials Science and
Engineering [M]. 5
th
ed. New York: John Wiley & Sons, 2001:422-426.

Unit 10
Text

Unit 10
Ceramic Structures — Crystalline and
Noncrystalline
The first level of structure above atomic structure involves the arrangement of
atoms. This level can have varying degrees of order or periodicity in the
arrangements, from no order to long range order. A monatomic gas at high
temperature and low pressure is an example of disorder or no order. An atom could
be anywhere within the enclosing volume and have no particular spatial relationship
with any of the other atoms. Single crystals have long range order throughout
(except at the surface) and are characterized by a repeating (periodic) arrangement
of identical structural units in space.
①
Solid materials may be classified according to the regularity with which atoms
or ions are arranged with respect to one another. A crystalline material is one in
which the atoms are situated in a repeating or periodic array over large atomic
distances; that is, long-range order exists, such that upon solidification, the atoms
will position themselves in a repetitive three-dimensional pattern, in which each
atom is bonded to its nearest-neighbor atoms. All metals, many ceramic materials,
and certain polymers form crystalline structures under normal solidification
conditions. For those that do not crystallize, this long-range atomic order is absent,
and they are referred to as noncrystalline or amorphous materials. Amorphous solids
have structures similar to liquids and generally have isotropic (the same in all







[] adj. 晶态的



[]
adj. [化]单原子的
[] adj. 空间的











[] adj. 无定形的
[] adj. 各向同性

directions) properties while crystalline solids usually have anisotropic (not the same
in all directions) properties.
Some of the properties of crystalline solids depend on the crystal structure of
the material, the manner in which atoms, ions, or molecules are spatially arranged.
There is an extremely large number of different crystal structures all having
long-range atomic order; these vary from relatively simple structures for metals, to
exceedingly complex ones, as displayed by some of the ceramic and polymeric







materials.
Ceramic crystal structures
Because ceramics are composed of at least two elements, and often more, their
crystal structures are generally more complex than those for metals. The atomic
bonding in these materials ranges from purely ionic to totally covalent; many
ceramics exhibit a combination of these two bonding types, the degree of ionic
character being dependent on the electronegativities of the atoms.
②
For those
ceramic materials for which the atomic bonding is predominantly ionic, the crystal
structures maybe thought of as being composed of electrically charged ions instead
of atoms. The metallic ions, or cations, are positively charged, because they have
given up their valence electrons to the nonmetallic ions, or anions, which are
negatively charged. Two characteristics of the component ions in crystalline ceramic
materials influence the crystal structure: the magnitude of the electrical charge on
each of the component ions, and the relative sizes of the cations and anions. With
regard to the first characteristic, the crystal must be electrically neutral; that is, all
the cation positive charges must be balanced by an equal number of anion negative
charges. The chemical formula of a compound indicates the ratio of cations to
anions, or the composition that achieves this charge balance. For example, in
calcium fluoride, each calcium ion has a +2 charge (Ca
2+
), and associated with each
fluorine ion is a single negative charge (F
-
). Thus, there must be twice as many F
-
as
Ca
2+
ions, which is reflected in the chemical formula CaF
2
.
The second criterion involves the sizes or ionic radii of the cations and anions,
r
C
and r
A
, respectively. Because the metallic elements give up electrons when
ionized, cations are ordinarily smaller than anions, and, consequently, the ratio r
C
r
A

is less than unity.
③
Each cation prefers to have as many nearest-neighbor anions as
possible. The anions also desire a maximum number of cation nearest neighbors.
Stable ceramic crystal structures form when those anions surrounding a cation
are all in contact with that cation, as illustrated in Fig. 10.1. The coordination
number (i.e., number of anion nearest neighbors for a cation) is related to the
cation-anion radius ratio. For a specific coordination number, there is a critical or
minimum r
C
r
A
ratio for which this cation-anion contact is established (Fig. 10.1),
this ratio may be determined from pure geometrical considerations.
④
For example,
if r
C
r
A
has a value between 0.155 and 0.225, the coordination number for the cation
is 3. This means each cation is surrounded by three anions in the form of a planar
equilateral triangle, with the cation located in the center.



[❖
n. 电负性










[()] n. 氟化物



[❖] adv. 分别地




[
] n. 配位数

Fig. 10.1 Stable and unstable anion-cation coordination configurations.
Open circles represent anions; colored circles denote cations.
A number of ceramic crystal structures may also be considered in terms of




n. 单位晶胞
prep. 在...的顶上



close-packed planes of ions, as well as unit cells. Ordinarily, the close-packed planes
are composed of the large anions. As these planes are stacked atop each other, small
interstitial sites are created between them in which the cations may reside.
These interstitial positions exist in two different types, as illustrated in Fig.
10.2. Four atoms (three in one plane, and a single one in the adjacent plane)
surround one type, labeled T in the figure; this is termed a tetrahedral position, since
straight lines drawn from the centers of the surrounding spheres form a four- sided
tetrahedron. The other site type, denoted as O in Fig. 10.2, involves six ion spheres,
three in each of the two planes. Because an octahedron is produced by joining these
six sphere centers, this site is called an octahedral position. Thus, the coordination
numbers for cations filling tetrahedral and octahedral positions are 4 and 6,
respectively. Furthermore, for each of these anion spheres, one octahedral and two
tetrahedral positions will exist.

Fig. 10.2 The stacking of one plane of close- packed spheres (anions)
on top of another; tetrahedral and octahedral positions between the planes
are designated by T and O, respectively.
(From W. G. Moffatt, G. W. Pearsall, and J. Wulff, The Structure and
Properties of Materials, Vol. 1, Structure. 1964, New York, John Wiley & Sons.)
Ceramic crystal structures of this type depend on two factors: (1) the stacking
of the close-packed anion layers (both FCC and HCP arrangements are possible,
which correspond to ABCABC... and ABABAB... sequences, respectively), and (2)
the manner in which the interstitial sites are filled with cations. For example,
consider the rock salt crystal structure. The unit cell has cubic symmetry, and each
cation (Na
+
ion) has six Cl
-
ion nearest neighbors. That is, the Na
+
ion at the center
has as nearest neighbors the six Cl
-
ions that reside at the centers of each of the cube
[] adj. 四面体

[] n. 八面体





















[] n. 次序









[ ] n. [矿]闪锌矿

faces. The crystal structure, having cubic symmetry, maybe considered in terms of
an FCC array of close- packed planes of anions, and all planes are of the {111} type.
⑤
The cations reside in octahedral positions because they have as nearest neighbors
six anions. Furthermore, all octahedral positions are filled, since there is a single
octahedral site per anion, and the ratio of anions to cations is 1:1. Other, but not all,
ceramic crystal structures may be treated in a similar manner; included are the zinc
blende and perovskite structures. The spinel structure is one of the A
m
B
n
X
p
types,
which is found for magnesium aluminate spinel (MgAl
2
O
4
). With this structure, the
O
2-
ions form an FCC lattice, whereas Mg
2+
ions fill tetrahedral sites and Al
3+
reside
in octahedral positions.
Since there are many different possible crystal structures, it is sometimes
convenient to divide them into groups according to unit cell configurations andor
atomic arrangements. One such scheme is based on the unit cell geometry, that is,
the shape of the appropriate unit cell parallelepiped without regard to the atomic
positions in the cell. Within this framework, an x, y, z coordinate system is
established with its origin at one of the unit cell corners; each of the x, y, and z axes
coincides with one of the three parallelepiped edges that extend from this corner, as
⑥
illustrated in Fig. 10.3. The unit cell geometry is completely defined in terms of six
parameters: the three edge lengths a, b, and c, and the three interaxial angles,

,


and

. These are indicated in Fig. 10.3, and are sometimes termed the lattice
parameters of a crystal structure. On this basis there are found crystals having seven
different possible combinations of a, b, and c, and

,

and

, each of which
represents a distinct crystal system. These seven crystal systems are cubic,
tetragonal, hexagonal, orthorhombic, rhombohedral, monoclinic, and triclinic. The
cubic system, for which a=b=c and

=

=

=90, has the greatest degree of
symmetry. Least symmetry is displayed by
the triclinic system, since abc and





.



Fig. 10.3 A unit cell with x, y, and z
coordinate axes, showing axial lengths (a, b
and c) and interaxial angles (

,

and

).


[❖] n. 钙钛矿
[] n. 尖晶石





[]
n. [数]平行六面体
[] n. 坐标



[] n. 点阵



[] adj. 四方的
[] adj.六方的
[] adj.正交的
[]
adj. 菱方的
[] adj. 单斜的
[] adj. 三斜的








Noncrystalline solids
It has been mentioned that noncrystalline solids lack a systematic and regular
arrangement of atoms over relatively large atomic distances. Sometimes such
materials are also called amorphous (meaning literally without form), or
supercooled liquids, in as much as their atomic structure resembles that of a liquid.
An amorphous condition may be illustrated by comparison of the crystalline
and noncrystalline structures of the compound silicon dioxide (SiO
2
), which may
exist in both states. Fig. 10.4 a and 10.4 b present two- dimensional schematic

diagrams for both structures of SiO
2
, in which the
SiO
4
4
tetrahedron is the basic
unit. Even though each silicon ion bonds to four oxygen ions for both states, beyond
this, the structure is much more disordered and irregular for the noncrystalline
structure.

Fig. 10.4 Two-dimensional schemes of the structure of
(a) crystalline silicon dioxide and (b) noncrystalline silicon dioxide.
Whether a crystalline or amorphous solid forms depends on the ease with
which a random atomic structure in the liquid can transform to an ordered state
⑦
during solidification. Amorphous materials, therefore, are characterized by atomic
or molecular structures that are relatively complex and become ordered only with
some difficulty. Furthermore, rapidly cooling through the freezing temperature
favors the formation of a noncrystalline solid, since little time is allowed for the
ordering process.
Reference: Donald R. Askeland, Pradeep P. Phulé. Essentials of Materials
Science and Engineering [M]. Canada: Nelson, a division of Thomson Canada
Limited, 2004
William D. Callister, Jr. Fundamentals of Materials Science and Engineering
[M]. 5
th
ed. New York: John Wiley & Sons, 2001:38-49,64-65.


Notes
1． Single crystals have long range order throughout (except at the surface) and are characterized
by a repeating (periodic) arrangement of identical structural units in space.
单晶整体具有长程有序性（表面除外），其特点是完全相同的结构单元在空间的重复（周
期性的）排列。
2． The atomic bonding in these materials ranges from purely ionic to totally covalent; many
ceramics exhibit a combination of these two bonding types, the degree of ionic character
being dependent on the electronegativities of the atoms.
陶瓷材料中原子间键的变化 范围可以从纯的离子键到完全的共价键；许多陶瓷既具有离

子键的特性又具有共价键的特 性，离子键特性的强弱取决于原子的电负性大小。
3． Because the metallic elements give up electrons when ionized, cations are ordinarily smaller
than anions, and, consequently, the ratio r
C
r
A
is less than unity.
因为金属元素在离子化的时候失去电子，所以阳离子通常比阴离子 小，导致比值r
C
r
A
小于1。
4． For a specific coordination number, there is a critical or minimum r
C
r
A
ratio for which this
cation-anion contact is established (Fig. 10.1), this ratio may be determined from pure
geometrical considerations.
为了使阴阳离子保持接触（见图 10.1），对于一个特定的配位数有一个临界的或最小的
r
C
r
A
比值，仅从几何角度即可确定这个比值。
5． The crystal structure, having cubic symmetry, maybe considered in terms of an FCC array of
close-packed planes of anions, and all planes are of the {111} type.
可以根据面心立方结构的阴离子密排面来考虑具有立方对称性的晶体的结构，所有的密
排面都属于{11 1}晶面族。
6． Within this framework, an x, y, z coordinate system is established with its origin at one of the
unit cell corners; each of the x, y, and z axes coincides with one of the three parallelepiped
edges that extend from this corner, as illustrated in Fig. 10.3.
在这个结构中建立一 个x、y、z坐标系，它的原点在单位晶胞的某个角顶上；x、y和z
三个轴分别从这个角顶伸出，并与 平行六面体的三条棱重合，如图10.3所示。
7． Whether a crystalline or amorphous solid forms depends on the ease with which a random
atomic structure in the liquid can transform to an ordered state during solidification.
究竟是形成晶态固体还是非晶态固体，取决于凝固过程中液体内随机 排列的原子结构转
变成为有序状态的难易程度。

Exercises
1．Reading comprehensions
(1)What are the differences between crystalline and noncrystalline structures?
(2)Please enumerate the seven crystal systems.
(3)What is coordination number? Which factor can influence it?

2．Choose the best answer to each of the following questions
(1)Which type of bond is not exist in ceramics
(a) ionic bond
(b) covalent bond
(c) metallic bond
(d) Van der Waals bond
(2)The coordination number of cations filling octahedral interstitial positions is
(a) 4
(b) 6
(c) 8
(3)In the rock salt crystal structure, what’s the ratio of octahedral positions that are filled
(a) 12
(b) 14

(c) 1
(4)The characteristics of lattice parameters of the cubic system are
(a) a=b=c and

=

=

=90
(b) a=bc and

=

=

=90
(c) a=b=c and







3．Translate the following into English
晶态固 体；立方晶系；四方晶系；单斜晶系；共价键；对称性；配位数；长程有序；单晶；
晶胞；阳离子

4．Translate the following into Chinese
① rhombohedral; hexagonal; parallelepiped; cation; coordinate system; monatomic; FCC; HCP;
electronegativity
② A crystalline material is one in which the atoms are situated in a repeating or periodic array
over large atomic distances; that is, long-range order exists, such that upon solidification, the
atoms will position themselves in a repetitive three- dimensional pattern, in which each atom is
bonded to its nearest-neighbor atoms.
③ With this structure, the O
2-
ions form an FCC lattice, whereas Mg
2+
ions fill tetrahedral sites
and Al
3+
reside in octahedral positions.
Furthermore, rapidly cooling through the freezing temperature favors the formation of a
noncrystalline solid, since little time is allowed for the ordering process.


Supplementary Reading
Crystal structures and defects in crystals
Crystal structures
When describing crystalline structures, atoms (or ions) are thought of as being solid spheres
having well- defined diameters. This is termed the atomic hard sphere model in which spheres
representing nearest-neighbor atoms touch one another. The long-range repetition of the same
atomic arrangement is conveniently described by a regular grid-like pattern called a lattice. This
array of points provides a structure that repeats endlessly through space with the same atom or
group of atoms associated with each point.
The atomic order in crystalline solids indicates that small groups of atoms form a repetitive
pattern. Thus, in describing crystal structures, it is often convenient to subdivide the structure into
small repeat entities called unit cells. Unit cells for most crystal structures are parallelepipeds or
prisms having three sets of parallel faces. A unit cell is chosen to represent the symmetry of the
crystal structure, where in all the atom positions in the crystal may be generated by translations of
the unit cell integral distances along each of its edges. Thus, the unit cell is the basic structural unit
or building block of the crystal structure and defines the crystal structure by virtue of its geometry
and the atom positions within. Furthermore, more than a single unit cell may be chosen for a
particular crystal structure; however, we generally use the unit cell having the highest level of