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1、精选优质文档-倾情为你奉上P2 Material science is the investigation of the relationship among processing, structure, properties, and performance of materials. 材料科学是研究材料的加工，组织性能和功能之间关系的学科（材料与工程之间的关系可以用图一的四面体来表示）P2 The discipline of materials science involves investigating the relationships that exist between the s
2、tructures and properties of materials. 材料科学是研究材料的结构和性能之间的关系的学科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. 而材料加工是在材料组织和性能关系的基础上，对材料的组织进行设计，以获得一系列预定的性能P5
3、 Semiconductors have electrical properties that are intermediate between the electrical conductors and insulators. Furthermore, the electrical characteristics of these materials are extremely sensitive to the presence of minute concentrations of impurity atoms, which concentrations may be controlled
4、 over very small spatial regions. The semiconductors have made possible the advent of integrated circuitry that has totally revolutionized the electronics and computer industries. 半导体有介于电导体和绝缘体之间的性能。此外这些材料做成的仪器对极小浓度的混杂原子特别灵敏这种混杂原子可以在非常小的空间区域控制起来半导体使集成电路有可能到来，集成电路彻底改变了电子行业和计算机行业 P5 Composites are for
5、med from two or more materials, producing properties that cannot be obtained by any single materials. Concrete and fiberglass are typical examples of composite materials. A composite is designed to display a combination of the best characteristics of each of the component materials. With composites
6、we can produce lightweight, strong, ductile, high temperature-resistant materials that are otherwise unobtainable, or produce hard yet shock-resistant cutting tools that would otherwise shatter. 复合材料是由两个或两个以上的材料复合而成生成单一材料得不到的性能。混凝土和玻璃纤维都是复合材料典型的例子。一个合成物是设计用来展现每个材料成分最佳特性的组合。用复合材料我们可以生产出轻质、强度高塑性好，难获得的
7、耐高温材料或者生产出坚硬的、的抗冲击性强而不破碎的切削工具P25 Many time, the physical properties and, in particular,the mechanical behavior of a material depend on the microstructure .Microstructure is subject to direct microscopic observation, using optical or electron microscopes.In many alloy, microstructure is characterized
8、 by the number of phase present, their proportions, and the manner in which they are distributed or arranged.The microstructure of an alloy depends on such variables as the alloying elements present, their concentration, and the heat treatment of the alloyP36 In addition to pearlite,other microconst
9、ituents that are products of the austenitic transformation exist;one of these is called bainite.The microstructure of bainite consists of ferrite and cementite phases, and thus diffusional processes are involved in its formation. Bainite forms as needles or plates, depending on the temperature of th
10、e transforrnation除了珠光体之外，其他的微观结构也是奥氏体转变的产物。其中一个就叫做贝氏体。贝氏体的微观结构是由铁素体和渗碳体所组成，因此在它的形成中包括的扩散的过程。贝氏体的外形是针状还是板条状取决于转变时的温度P37 Another mcroconstituent or phase called is formed when austenitized iron-carbon alloys are rapidly cooled to a relatively low temperature. Martensite is a nonequilibrium single phas
11、e structure that results from a diffusionless transformation of austenite. The martensitic transformation occurs when the quenching rate is rapidenough to prevent carbon diffusion. Any diffusion whatsoever will result in the formation of ferrite and cementite phases.当奥氏体化的铁碳合金被快速的冷却到一个相对低的温度时，另外一个叫做
12、马氏体的微观结构或者说是相就会形成。马氏体是一个非平衡单相组织，它是由奥氏体的非扩散转变而形成的。当淬火时的速度快的足以去阻止碳扩散时，马氏体的转变就会发生。无论什么样的扩散（转变）都会导致铁素体相和渗碳体相的形成 P40 After yielding,the stress necessary to continue plastic deformation in metals increases to a maximum,point M in Figure 1.26,and then decreases to the eventual fracture,point F . The tensil
13、e strength is the stress at the maximum on the engineering stress strain curve. This corresponds to the maximum stress that can be sustained by a structure in tension. If this stress is applied and maintained,fracture will result. All deformation up to this point is uniform throughout the narrow reg
14、ion of the tensile specimen. However,at this maximum stress,a small constriction or neck begins to form at some point, and all subsequent deformation is confined at this neck,as indicated by the schematic specimen insets in Figure1.26. This phenomenon is termed “necking,”and fracture ultimately occu
15、rs at the neck抗拉强度屈服之后，金属持续发生塑性变形的应力会达到一个最大值，图表1.2中的M点，然后减小直到最终断裂F点。抗拉强度b就是工程应力应变曲线上最大值时的应力。这和组织所能维持的拉力的最大应力相一致。如果这应力施加并保持就会引起断裂。在受拉试样的狭小区域整个范围内达到这一点时的所有变形都是均匀的。然而在这个最大应力处，有小的或缩颈开始在某一处形成，随后的变形就限制在缩颈处如插图1.26中的试样，这种现象叫做颈缩，并且断裂基本上就在经缩处。一般的当材料的强度被用以设计时就要利用屈服强度，这是因为当施加的应力达到抗拉强度时，组织会因发生强烈的塑性变形而改变而不能使用P72
16、Steels with a carbon range of 0.05 to .0.30 percent are called low-carbon steels. Steels in this class are tough, ductile, and easily machined, formed, and welded. Most of them do not respond to any heat treating process except case hardening. 碳含量从0.05%到0.30%的钢被称为低碳钢。这类钢韧性好塑性好容易加工形成和焊接。除了表面渗碳硬化大部分对任何热处理没有回应。P72 Those steels have a carbon range from 0.30to0.45 percent. They are strong and hard but cannot be worked or welded
