材料科学与工程第四版部分翻译

1、精选优质文档-倾情为你奉上精选优质文档-倾情为你奉上专心-专注-专业专心-专注-专业精选优质文档-倾情为你奉上专心-专注-专业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 invest

2、igating the relationships that exist between the structures 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 propert

3、ies. 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 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 impu

4、rity atoms, which concentrations may be controlled 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

5、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 formed 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

6、 each of the component materials. With composites 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

7、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 microsco

8、pes.In many alloy, microstructure is characterized 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

9、 alloyP36 In addition to pearlite,other microconstituents 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 nee

10、dles or plates, depending on the temperature of the 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 tempe

11、rature. Martensite is a nonequilibrium single phase 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

12、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 decre

13、ases to the eventual fracture,point F . The tensile 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

14、to this point is uniform throughout the narrow region 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 phenomeno

15、n is termed “necking,”and fracture ultimately occurs 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

16、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 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.

17、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 as easily as low-carbon steels. Because of their higher carbon content, they can be heat treated. Successful welding of the

18、se steels often requires special electrodes, but even then greater care must be taken to prevent formation of cracks around the weld area.这类钢的碳含量从0.30%到0.45%。他们强度和硬度很高，但不能像低碳钢一样容易被加工和焊接。因为他们有更高的碳含量他们可以进行热处理。通常需要采用特殊焊条才能成功地焊接这类钢材P74 The addition of manganese to steel produces a fine grain structure w

19、hich has greater toughness and ductility. Manganese always presents in a steel to some extent because it is used as a deoxidiser. 在钢中加入锰会生成使金属有很好的韧性和塑性的细晶组织。锰总是一定程度出现在钢中因为它被用作脱氧剂。P74 Always present to some extent, because it is used with manganese as a deoxidiser. 总是一定程度的存在因为它和锰共同作为脱氧剂。P74 When quan

20、tities of chromium are added to steel the resulting product is a metal having extreme hardness and resistance to wear without making it brittle. Chromium also tends to refine the grain structure of steel, thereby increasing its toughness. It is used either alone in carbon steel or in combination wit

21、h other elements such as nickel, vanadium, molybdenum, or tungsten钢中加入大量的铬以后，硬度变得非常高，非常耐磨而又不脆。铬也能改善钢的晶粒组织，从而提高它的韧性。铬既可以单独使用在钢中，也可以和镍、钒、钼、钨等元素联合使用P117 It has for many years been one of the most common techniques applied to the fabrication of steels. The process uses an arc as the heat source and shie

22、lding is provided by gases generated by the decomposition of the electrode coating material and by the slag produced by the melting of mineral constituents of the coating.In addition to heating and melting the parent material the arc also melts the core of the electrode and thereby provides filler m

23、aterial for the joint .The electrode coating may also be used as a source of alloying elements and additional filler material. The flux and electrode chemistry may be formulated to deposit wearand corrosion resistant layers for surface protection.Significant features of the process are:(1)equipment

24、requirements are simple;(2)a large range of consumables are available;(3)the process is extremely portable;(3)the operating efficiency is low;(4)it is labour intensive很多年以来，手工电弧焊都是应用于钢的装配的最普通的技术之一。该工艺采用电弧作为热源，由焊条药皮分解产生的气体和药皮中的矿物质成分熔化形成的熔渣提供保护。除了加热和熔化母材，电弧也能熔化焊条的芯部，从而向接头处提供填充金属。焊条涂层可能也会被用来作为合金成分和其他的填

25、充材料的来源。为了保护（金属）表面，焊剂和焊条的化学相互作用可以被制定用来去形成抗磨损抗腐蚀的沉积物。手工电弧焊具有以下几个特点：1：设备简单。2：有大量的焊丝可供选用。3：这种方法非常的简单。4：操作效率低。5：劳动密集型技术P121 In the gas tungsten arc welding process the the heat generated by an arc which is maintained between the workpiece and a non-consumable tungsten electrode is used to fuse the joint

26、area . The arc is sustained in an inert gas which serves to protect the weld pool and the electrode from atmospheric contamination.The principle of operation is illustrated in Figure 3.8. (员)it is conducted in a chemically inert atmosphere;(1)the arc energy density is relatively high;(2)the process is very controllable;(3)joint quality is usually high;(4)deposition rates and joint completion rates are l