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1、目录12781112单元第一单元Types of Materials 材料类型 Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materials. 材料可以按多种方法分类。科学家常根据状态将材料分为：固体、液体或气体。他们也把材料分为有机材料(曾经有生
2、命)和无机材料(从未有生命)。 For industrial purposes, materials are divided into engineering materials or nonengineering materials. Engineering materials are those used in manufacture and become parts of products. 就工业效用而言，材料被分为工程材料和非工程材料。那些用于加工制造并成为产品组成局部就是工程材料。Nonengineering materials are the chemicals, fuels,
3、lubricants, and other materials used in the manufacturing process, which do not become part of the product.非工程材料那么是化学品、燃料、润滑剂以及其它用于加工制造过程但不成为产品组成局部材料。 Engineering materials may be further subdivided into: Metal Ceramics Composite Polymers, etc. 工程材料还能进一步细分为：金属材料陶瓷材料复合材料 聚合材料，等等。Metals and Metal Allo
4、ys 金属和金属合金 Metals are elements that generally have good electrical and thermal conductivity. Many metals have high strength, high stiffness, and have good ductility. 金属就是通常具有良好导电性和导热性元素。许多金属具有高强度、高硬度以及良好延展性。Some metals, such as iron, cobalt and nickel, are magnetic. At low temperatures, some metals
5、and intermetallic compounds become superconductors.某些金属能被磁化，例如铁、钴和镍。在极低温度下，某些金属和金属化合物能转变成超导体。 What is the difference between an alloy and a pure metal Pure metals are elements which come from a particular area of the periodic table. Examples of pure metals include copper in electrical wires and alum
6、inum in cooking foil and beverage cans. 合金与纯金属区别是什么？纯金属是在元素周期表中占据特定位置元素。例如电线中铜和制造烹饪箔及饮料罐铝。Alloys contain more than one metallic element. Their properties can be changed by changing the elements present in the alloy. Examples of metal alloys include stainless steel which is an alloy of iron, nickel,
7、and chromium; and gold jewelry which usually contains an alloy of gold and nickel.合金包含不止一种金属元素。合金性质能通过改变其中存在元素而改变。金属合金例子有：不锈钢是一种铁、镍、铬合金，以及金饰品通常含有金镍合金。 Why are metals and alloys used Many metals and alloys have high densities and are used in applications which require a high mass-to-volume ratio. 为什么
8、要使用金属和合金？许多金属和合金具有高密度，因此被用在需要较高质量体积比场合。Some metal alloys, such as those based on aluminum, have low densities and are used in aerospace applications for fuel economy. Many alloys also have high fracture toughness, which means they can withstand impact and are durable.某些金属合金，例如铝基合金，其密度低，可用于航空航天以节约燃料。
9、许多合金还具有高断裂韧性，这意味着它们能经得起冲击并且是耐用。 What are some important properties of metals Density is defined as a materials mass divided by its volume. Most metals have relatively high densities, especially compared to polymers. 金属有哪些重要特性？ 密度定义为材料质量与其体积之比。大多数金属密度相对较高，尤其是和聚合物相比拟而言。Materials with high densities of
10、ten contain atoms with high atomic numbers, such as gold or lead. However, some metals such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight.高密度材料通常由较大原子序数原子构成，例如金和铅。然而，诸如铝和镁之类一些金属那么具有低密度，并被用于既需要金属特性又要求重量轻场合。
11、 Fracture toughness can be described as a materials ability to avoid fracture, especially when a flaw is introduced. Metals can generally contain nicks and dents without weakening very much, and are impact resistant. A football player counts on this when he trusts that his facemask wont shatter. 断裂韧
12、性可以描述为材料防止断裂特别是出现缺陷时不断裂能力。金属一般能在有缺口和凹痕情况下不显著削弱，并且能抵抗冲击。橄榄球运发动据此相信他面罩不会裂成碎片。 Plastic deformation is the ability of bend or deform before breaking. As engineers, we usually design materials so that they dont deform under normal conditions. You dont want your car to lean to the east after a strong west
13、 wind. 塑性变形就是在断裂前弯曲或变形能力。作为工程师，设计时通常要使材料在正常条件下不变形。没有人愿意一阵强烈西风过后自己汽车向东倾斜。However, sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before they break.然而，有时我们也能利用塑性变形。汽车上压皱区域在它们断裂前通过经历塑性变形来吸收能量。 The atomic bonding of meta
14、ls also affects their properties. In metals, the outer valence electrons are shared among all atoms, and are free to travel everywhere. Since electrons conduct heat and electricity, metals make good cooking pans and electrical wires. 金属原子连结对它们特性也有影响。在金属内部，原子外层阶电子由所有原子共享并能到处自由移动。由于电子能导热和导电，所以用金属可以制造好
15、烹饪锅和电线。It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the metal. No photons pass through.因为这些阶电子吸收到达金属光子，所以透过金属不可能看得见。没有光子能通过金属。 Alloys are compounds consisting of more than one metal. Adding other metals can affect the density, strength
16、, fracture toughness, plastic deformation, electrical conductivity and environmental degradation. 合金是由一种以上金属组成混合物。加一些其它金属能影响密度、强度、断裂韧性、塑性变形、导电性以及环境侵蚀。For example, adding a small amount of iron to aluminum will make it stronger. Also, adding some chromium to steel will slow the rusting process, but w
17、ill make it more brittle.例如，往铝里加少量铁可使其更强。同样，在钢里加一些铬能减缓它生锈过程，但也将使它更脆。Ceramics and Glasses陶瓷和玻璃 A ceramic is often broadly defined as any inorganic nonmetallic material By this definition, ceramic materials would also include glasses; however, many materials scientists add the stipulation that “cerami
18、c must also be crystalline. 陶瓷通常被概括地定义为无机非金属材料。照此定义，陶瓷材料也应包括玻璃；然而许多材料科学家添加了“陶瓷必须同时是晶体物组成约定。 A glass is an inorganic nonmetallic material that does not have a crystalline structure. Such materials are said to be amorphous. 玻璃是没有晶体状构造无机非金属材料。这种材料被称为非结晶质材料。Properties of Ceramics and Glasses Some of the
19、 useful properties of ceramics and glasses include high melting temperature, low density, high strength, stiffness, hardness, wear resistance, and corrosion resistance.陶瓷和玻璃特性 高熔点、低密度、高强度、高刚度、高硬度、高耐磨性和抗腐蚀性是陶瓷和玻璃一些有用特性。Many ceramics are good electrical and thermal insulators. Some ceramics have speci
20、al properties: some ceramics are magnetic materials; some are piezoelectric materials; and a few special ceramics are superconductors at very low temperatures. Ceramics and glasses have one major drawback: they are brittle.许多陶瓷都是电和热良绝缘体。某些陶瓷还具有一些特殊性能：有些是磁性材料，有些是压电材料，还有些特殊陶瓷在极低温度下是超导体。陶瓷和玻璃都有一个主要缺点：它
21、们容易破碎。 Ceramics are not typically formed from the melt. This is because most ceramics will crack extensively (i.e. form a powder) upon cooling from the liquid state. 陶瓷一般不是由熔化形成。因为大多数陶瓷在从液态冷却时将会完全破碎(即形成粉末)。Hence, all the simple and efficient manufacturing techniques used for glass production such as
22、 casting and blowing, which involve the molten state, cannot be used for the production of crystalline ceramics. Instead, “sintering or “firing is the process typically used. 因此，所有用于玻璃生产简单有效诸如浇铸和吹制这些涉及熔化技术都不能用于由晶体物组成陶瓷生产。作为替代，一般采用“烧结或“焙烧工艺。In sintering, ceramic powders are processed into compacted s
23、hapes and then heated to temperatures just below the melting point. At such temperatures, the powders react internally to remove porosity and fully dense articles can be obtained.在烧结过程中，陶瓷粉末先挤压成型然后加热到略低于熔点温度。在这样温度下，粉末内部起反响去除孔隙并得到十分致密物品。 An optical fiber contains three layers: a core made of highly p
24、ure glass with a high refractive index for the light to travel, a middle layer of glass with a lower refractive index known as the cladding which protects the core glass from scratches and other surface imperfections, and an out polymer jacket to protect the fiber from damage. 光导纤维有三层：核心由高折射指数高纯光传输玻
25、璃制成，中间层为低折射指数玻璃，是保护核心玻璃外表不被擦伤和完整性不被破坏所谓覆层，外层是聚合物护套，用于保护光导纤维不受损。In order for the core glass to have a higher refractive index than the cladding, the core glass is doped with a small, controlled amount of an impurity, or dopant, which causes light to travel slower, but does not absorb the light. 为了使核心
26、玻璃有比覆层大折射指数，在其中掺入微小、可控数量能减缓光速而不会吸收光线杂质或搀杂剂。Because the refractive index of the core glass is greater than that of the cladding, light traveling in the core glass will remain in the core glass due to total internal reflection as long as the light strikes the core/cladding interface at an angle greate
27、r than the critical angle. 由于核心玻璃折射指数比覆层大，只要在全内反射过程中光线照射核心/覆层分界面角度比临界角大，在核心玻璃中传送光线将仍保存在核心玻璃中。The total internal reflection phenomenon, as well as the high purity of the core glass, enables light to travel long distances with little loss of intensity.全内反射现象与核心玻璃高纯度一样，使光线几乎无强度损耗传递长距离成为可能。Composites 复合
28、材料 Composites are formed from two or more types of materials. Examples include polymer/ceramic and metal/ceramic composites. Composites are used because overall properties of the composites are superior to those of the individual components. 复合材料由两种或更多材料构成。例子有聚合物/陶瓷和金属/陶瓷复合材料。之所以使用复合材料是因为其全面性能优于组成局部
29、单独性能。For example: polymer/ceramic composites have a greater modulus than the polymer component, but arent as brittle as ceramics. Two types of composites are: fiber-reinforced composites and particle-reinforced composites.例如：聚合物/陶瓷复合材料具有比聚合物成分更大模量，但又不像陶瓷那样易碎。 复合材料有两种：纤维加强型复合材料和微粒加强型复合材料。Fiber-reinfo
30、rced Composites Reinforcing fibers can be made of metals, ceramics, glasses, or polymers that have been turned into graphite and known as carbon fibers. Fibers increase the modulus of the matrix material. 纤维加强型复合材料 加强纤维可以是金属、陶瓷、玻璃或是已变成石墨被称为碳纤维聚合物。纤维能加强基材模量。The strong covalent bonds along the fibers
31、length give them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved.沿着纤维长度有很强结合力共价结合在这个方向上给予复合材料很高模量，因为要损坏或拉伸纤维就必须破坏或移除这种结合。 Fibers are difficult to process into composites, making fiber-reinforced composites relatively expensive. 把纤维放入复
32、合材料较困难，这使得制造纤维加强型复合材料相对昂贵。Fiber-reinforced composites are used in some of the most advanced, and therefore most expensive sports equipment, such as a time-trial racing bicycle frame which consists of carbon fibers in a thermoset polymer matrix. 纤维加强型复合材料用于某些最先进也是最昂贵运动设备，例如计时赛竞赛用自行车骨架就是用含碳纤维热固塑料基材制成。
33、Body parts of race cars and some automobiles are composites made of glass fibers (or fiberglass) in a thermoset matrix. 竞赛用汽车和某些机动车车体部件是由含玻璃纤维(或玻璃丝)热固塑料基材制成。 Fibers have a very high modulus along their axis, but have a low modulus perpendicular to their axis. Fiber composite manufacturers often rota
34、te layers of fibers to avoid directional variations in the modulus. 纤维在沿着其轴向有很高模量，但垂直于其轴向模量却较低。纤维复合材料制造者往往旋转纤维层以防模量产生方向变化。Particle-reinforced composites Particles used for reinforcing include ceramics and glasses such as small mineral particles, metal particles such as aluminum, and amorphous materi
35、als, including polymers and carbon black.微粒加强型复合材料 用于加强微粒包含了陶瓷和玻璃之类矿物微粒，铝之类金属微粒以及包括聚合物和碳黑非结晶质微粒。 Particles are used to increase the modulus of the matrix, to decrease the permeability of the matrix, to decrease the ductility of the matrix. An example of particle-reinforced composites is an automobil
36、e tire which has carbon black particles in a matrix of polyisobutylene elastomeric polymer. 微粒用于增加基材模量、减少基材渗透性和延展性。微粒加强型复合材料一个例子是机动车胎，它就是在聚异丁烯人造橡胶聚合物基材中参加了碳黑微粒。Polymers 聚合材料 A polymer has a repeating structure, usually based on a carbon backbone. The repeating structure results in large chainlike mo
37、lecules. Polymers are useful because they are lightweight, corrosion resistant, easy to process at low temperatures and generally inexpensive. 聚合物具有一般是基于碳链重复构造。这种重复构造产生链状大分子。由于重量轻、耐腐蚀、容易在较低温度下加工并且通常较廉价，聚合物是很有用。 Some important characteristics of polymers include their size (or molecular weight), soft
38、ening and melting points, crystallinity, and structure. The mechanical properties of polymers generally include low strength and high toughness. Their strength is often improved using reinforced composite structures. 聚合材料具有一些重要特性，包括尺寸(或分子量)、软化及熔化点、结晶度和构造。聚合材料机械性能一般表现为低强度和高韧性。它们强度通常可采用加强复合构造来改善。Impor
39、tant Characteristics of Polymers Size. Single polymer molecules typically have molecular weights between 10,000 and 1,000,000g/molthat can be more than 2,000 repeating units depending on the polymer structure! 聚合材料重要特性 尺寸：单个聚合物分子一般分子量为10,000到1,000,000g/mol之间，具体取决于聚合物构造这可以比2,000个重复单元还多。The mechanical
40、 properties of a polymer are significantly affected by the molecular weight, with better engineering properties at higher molecular weights.聚合物分子量极大地影响其机械性能，分子量越大，工程性能也越好。 Thermal transitions. The softening point (glass transition temperature) and the melting point of a polymer will determine which
41、it will be suitable for applications. These temperatures usually determine the upper limit for which a polymer can be used. 热转换性：聚合物软化点(玻璃状转化温度)和熔化点决定了它是否适合应用。这些温度通常决定聚合物能否使用上限。For example, many industrially important polymers have glass transition temperatures near the boiling point of water (100,
42、212), and they are most useful for room temperature applications. Some specially engineered polymers can withstand temperatures as high as 300(572).例如，许多工业上重要聚合物其玻璃状转化温度接近水沸点(100, 212)，它们被广泛用于室温下。而某些特别制造聚合物能经受住高达300(572)温度。 Crystallinity. Polymers can be crystalline or amorphous, but they usually ha
43、ve a combination of crystalline and amorphous structures (semi-crystalline). 结晶度：聚合物可以是晶体状或非结晶质，但它们通常是晶体状和非结晶质构造结合物(半晶体)。 Interchain interactions. The polymer chains can be free to slide past one another (thermo-plastic) or they can be connected to each other with crosslinks (thermoset or elastomer)
44、. Thermo-plastics can be reformed and recycled, while thermosets and elastomers are not reworkable. 原子链间相互作用：聚合物原子链可以自由地彼此滑动(热可塑性)或通过交键互相连接(热固性或弹性)。热可塑性材料可以重新形成和循环使用，而热固性与弹性材料那么是不能再使用。 Intrachain structure. The chemical structure of the chains also has a tremendous effect on the properties. Dependin
45、g on the structure the polymer may be hydrophilic or hydrophobic (likes or hates water), stiff or flexible, crystalline or amorphous, reactive or unreactive. 链内构造：原子链化学构造对性能也有很大影响。根据各自构造不同，聚合物可以是亲水或憎水(喜欢或讨厌水)、硬或软、晶体状或非结晶质、易起反响或不易起反响。第二单元 The understanding of heat treatment is embraced by the broader
46、 study of metallurgy. Metallurgy is the physics, chemistry, and engineering related to metals from ore extraction to the final product. 对热处理理解包含于对冶金学较广泛研究。冶金学是物理学、化学和涉及金属从矿石提炼到最后产物工程学。Heat treatment is the operation of heating and cooling a metal in its solid state to change its physical properties.
47、 According to the procedure used, steel can be hardened to resist cutting action and abrasion, or it can be softened to permit machining. 热处理是将金属在固态加热和冷却以改变其物理性能操作。按所采用步骤，钢可以通过硬化来抵抗切削和磨损，也可以通过软化来允许机加工。With the proper heat treatment internal stresses may be removed, grain size reduced, toughness increased, or a hard surface produced on a ductile interior. The analysis of the steel must be known because small percentages of certai