材料毕业设计翻译

1、本科毕业设计（论文）外文参考文献译文及原文 学 院 机电工程学院 专 业 机械设计制造及其自动化 （微电子制造装备及其自动化方向）年级班别 2008级（1）班 学 号 3108000629 学生姓名 杨慧明 指导教师 熊汉伟 2012年6月目 录外文参考文献译文2原 文11外文参考文献译文第三章 材料特性和分析 材料特性是鉴别材料的基础和用在逆向工程评估性能的一部分。其中在逆向工程中最经常被问到的问题是，用什么材料特性评定两种相同的材料。从理论上说，只有当两种材料的特性被对比并找出相同点后，才可以评定他们是相同的。这样的成本可能是非常高的，但在技术上的确是可行的。在工程实践中，当有足够的数据证

2、明两个材料有相关特性的价值时，通常会认为符合了可接受风险的要求。确定相关的材料特性和当量需要全面的了解材料和这种材料制成的部分功能。在逆向工程评估项目中，要想令人信服地解释有关材料的性能、属性、最终拉伸强度，疲劳强度，抗蠕变性，断裂韧性，工程师需要至少提供以下阐述：1、 特性重要性：解释相关的特性对零件的设计功能来说是多么重要。2、 风险评估：解释有关属性将如何影响器件的性能，这种材料的属性如果未能满足设计值会有什么潜在后果。3、 性能保证：说明对比原始材料，需要进行怎样的测试以显示其等效性。 本章的主要目的是讨论和着重于在逆向工程中材料特性与机械冶金的应用，以帮助读者完成这些工作任务。机械性

3、，冶金性能，物理化学特性，是进行逆向工程机械中最相关的材料特性部分。力学性能是与当用力时弹性和塑性的反应有关。主要力学性能包括抗拉强度，屈服强度，延展性，抗疲劳，抗蠕变性，应力断裂强度。他们通常反映的应力和应变之间的关系。许多力学性能与冶金性能和物理化学性质密切相关。 冶金性能是指金属元素和合金的物理和化学特性，如合金的微观结构和化学成分。这些特性是与热力学、动力学过程和通常在这些过程中发生的化学反应密切相关的。热力学的原理决定当两种元素混合在一起时能否被结合成合金成分。动力学过程决定合成的速度。热力学的原理常用于建立平衡相图，这有助于工程师设计新的合金和解释更多的冶金性能和反应。它需要一个很

4、长的时间才能达到平衡状态。因此，大部分的晶粒形貌和合金结构上的动力学过程取决于反应速率，如晶粒的增长速度。 热处理是一个过程，被广泛地使用，通过冶金反应获得最佳的机械性能。热处理应用于固体无机非金属材料，通过加热和冷却操作的反复结合来获得合适的组织形态甚至是理想的特性。最常用的适用于热处理工艺包括退火处理，固溶处理，老化处理。退火是一个过程，在特定温度加热下一段时间，然后再慢慢在特定的速度下降温。它主要用于软化金属，提高其可加工性和机械延展性。适当的退火也将增加材料层面的稳定性。最常见使用的退火工艺是完全退火，制程退火，等温退火，球化。当退火的唯一目的是为减小压力，该退火过程通常被称为消除应力

5、。它减少了由铸造，淬火，正火，加工，冷加工，或焊接引起的内部的残余应力。固溶热处理仅适用于合金，但不适用于纯金属。在这个过程中，合金被加热到特定温度以上，并在此温度下维持足够长的时间，使各组成元素溶合成固溶体，随后迅速冷却，以形成固溶体。结果，这个过程中产生过饱和，当合金冷却到一个较低的温度，其呈热力学不稳定状态，因为组成元素的溶解度随温度升高而降低。固溶热处理往往后续是老化处理以达到沉淀硬化。从热处理角度来看，老化处理描述了某些合金在随着时间，温度变化的特性。这是一个从过饱和固溶体状态变成沉淀的结果。老化硬化是最重要的强化硬化铝合金和镍基合金机制之一。 物理特性通常是指材料的固有特点。它们是

6、与化工，冶金，机械过程无关，如密度，熔融温度，传热系数，比热和电导率。材料的这些特性通常是不用任何的机械力测量。在许多工程应用中，这些属性是至关重要的。例如，比强度（每单位重量的强度）直接取决于合金的密度，当工程师设计飞机和汽车时它是比绝对抗拉强度更重要。然而，大多数的材料特性并不是完全独立的。他们之间会互相影响。因此，有些材料特性根据各自的功能既是机械特性又是物理特性，如杨氏系数和剪切系数。材料的一个准确的杨氏系数通常是由超声波技术测量的，而没有采用任何机械力。然而，杨氏系数通常也被称为应力和应变之间的比率，它们是在机械性能评价的关键要素。冶金和机械特性之间的相互关系，也导致一些材料性质分为

7、两类，如硬度和应力抗裂性能可以被称为冶金或机械性能。3.1合金结构当量3.1.1工程合金结构工程合金是工程应用中的金属物质，已广泛应用于许多行业数百年之久。例如，铝合金在航空业中的利用从一开始一直到今天；在1903年，莱特兄弟飞机的曲轴箱由铝合金铸造而成，两个或两个以上的元素组成的合金是拥有不同的属性的。当它们从液态冷却到固态，大多数合金会形成结晶结构，但没有结晶的将会凝固，像玻璃。金属玻璃的非晶结构，是一种金属元素的随机布局。相比之下，晶体结构根据合金元素有一个反复的样式。例如，铝的晶体结构4%的铜合金是基于铝与铜原子融合的晶体结构。衡量一种合金的性能如硬度，是它性质表现的一部分，和它的晶体

8、结构之下是其独特的通用结构。它们都在逆向工程的金属识别中发挥着关键的作用。纯金属元素，例如，铝、铜、和铁，它们的原子排列具有规律性。这种原子模式的排序顺序最小单位是单元。单个晶体是这些没有晶粒边界的单元在相同方向的聚合。它本质上是一个单一的原子有序排列成的巨大晶粒。这种独特的晶体结构，使单晶的力学性能特别明显，能够特殊应用。单晶镍基高温合金在现代飞机发动机涡轮叶片中得到应用。第一台单晶刃飞机的发动机是惠普jt9d-7r4，并在1982年获得美国联邦航空局的认证。它应用于很多飞机，例如波音767和空中客机a310。与对应的等轴晶粒对比，一个单一晶体的喷气发动机涡轮机翼可以抵抗更多次的腐蚀，和好得

9、多的蠕变强度和抗热疲劳性能。然而，大多数工程合金，有很多种形态。晶粒尺寸和其质地对其合金性能有很深远的影响。细粒工程合金在室温下通常具有较高的拉伸强度。然而，对于高温应用，粗晶粒合金由于其耐蠕变性能更好，为首选。微观结构对于工程合金性能的影响将在后面详细讨论。3.1.2工艺影响及产品材料的等价形式从不同的制造工艺和原材料生产的产品形式计算出结果的部分功能，特别是独特的微观结构，是广泛应用于确认逆向工程材料等效性的特点。传统的工程合金用于制造过程产生了一种特定的产品形式包括铸造，锻造，轧制，以为其他冷热工作。粉末冶金快速凝固，化学气相沉积法，以及许多其他特殊工艺，例如，鱼鹰喷射成形和超塑性成形，

10、也可用于针对特定应用的行业。一些近净型的过程，直接塑造成接近最终产品的形式或几何形状复杂的合金。在具有多个处理步骤的传统铸造和锻造产品中，从原材料到最终产品涉及较少步骤的简单转换往往是更可取的。例如，“鱼鹰”喷射成型过程雾化熔融的合金，形成一个环型的瓶坯硬件或密封的如发动机涡轮。近净型预制棒接着通过热等静压机制成最终的产品。一个鱼鹰喷射成形7a60合金镍基合金产品更具成本效益，它通常有一个约65微米的平均晶粒尺寸。它显示了一个类似的微观结构和可比物业锻造件具有相同的合金成分，并比铸造产品具有更好的性能。制造技术的最新进展中，生产了显微结构和纳米合金。工程合金的力学性能主要取决于两个要素：组成和

11、微观结构。尽管合金成分有特定的结构，但是微观结构在这过程中不断发展。因此，不同产品中工程合金的结构和力学性能是截然不同的。图3.1显示了铝合金铸件的晶粒结构。 （a）（b）图3.1 这在铝合金挤压成型中能观察到很不同的微观结构，如图3.1b所示，尽管这两者有相同的合金成分：铝-3.78%，铜-1.63%，锂-1.40%。不用多说，铸铝和挤压铝箔也一样有非常不同的特性。在逆向工程中，该微观结构在零件的制造过程中提供了重要的信息。3.2 物相的定性与定量 相图是根据相变过程建立起来的。它说明了合金成分，相位和温度之间的关系。它提供了各种制造和热处理工艺的参考指南。从相图中提取的信息对物相鉴定起了重

12、要作用，因此它在逆向工程中对制造工艺和热处理验证也是至关重要的。本节将讨论相图和热力学和动力学的相关理论的基础。3.2.1 相图 合金相图是一个冶金插图，显示熔化和凝固温度以及合金在特定温度下的不同阶段。平衡相图显示了各平衡相的函数成分和温度。根据推定，动力学反应过程在每一步是足够快地达到平衡状态。这本书中，除了另有指明之外，下面所有的相图都指的是平衡相图。图3.2只是是一个部分的铁碳相图（fe-c），因为这个图非常复杂所以无法全部完成。相图的y轴是温度，x轴表示合金元素组成量。二元fe-c相图中，铁是主要的基本元素，碳是合金元素。最左边的y轴代表纯铁，也就是100的铁。温度铁 碳的百分含量图

13、3.2 部分的fe-c相示意图。图的横坐标从左到右增加含碳量。合金元素的单位通常是百分比含量，但偶尔使用原子百分比含量。有时在图的底部或顶部标记百分点符号。图3.2中显示的碳含量范围从0到6.7。含碳量6.7的 fe是一种金属互化物，碳化铁。合金的各构成要素可能由范围固定的或窄的成分合并成一个独特的复合合金。这些化合物是金属化合物。大多数金属化合物有自己的特性，有特定的成分和独特的晶体结构及性能。碳化铁fe3c，是有色铁碳合金中最常见的金属化合物。大多数的fe-c二元相图是fe-fe3c相图，用fe3c而不是100纯碳作基线图。j.威拉德吉布斯相律和热力学法例相律指导金属相变相关知识。吉布斯相

14、律通过数学公式3.1描述，其中f是自由或独立变量，c是元素数量，而p是在热力学平衡系统中的相数。 f = c p + 2 (3.1)典型的独立变量是温度和压力。大多数相图假设在大气压力下。当合金熔化，固体和液体并存，因此，p =2。吉布斯相律只允许在纯金属中有一个独立变量，其中c= 1。这说明，在大气压力下，纯金属在一个特定的熔融温度下熔化以及一个固定的沸点下沸腾。例如，在图3.2中纯铁的熔化温度标记为1534c。然而，二元合金，其中c= 2，吉布斯相律允许更多的独立变量。对于一个给定的组成，二元合金的液固相变温度是在一定的温度范围内，而不是某一个固定的温度。图3.2所示，在1,400c，fe

15、-3c二元合金是均匀的液体状态。当温度降低到液相温度以下（1300c左右）它会开始凝固。在相图中液相是存在于液体开始凝固的温度边界内。换句话说，液相开始与各种成分的合金熔化温度。在图3.2中，液相表示由1534c时的纯液态铁融化温度曲线持续到1147c时的fe-4.3c熔融温度曲线之间. fe-4.3c被定义为共晶成分。尽管这是一个二元合金，但是它是在1147c这个固定的温度融化，因为这两个不同的固相能在同一温度凝固。如图3.2所示，共晶温度是最低的铁碳合金熔化温度。完成凝固温度的曲线被定义为固相线。上述合金的液相是均匀的液体状态，它通常被称为液相或液体溶液，并在许多相图中标记为l。下面的合金

16、固相线是一个均匀的固态，这通常被称为作为固相或固溶体。各种合金的固相通常用指定的希腊字母，从左边开始表示相，继续由相图右移，按顺序地表示，相。对于 fe3 %c合金，新形成的固相和剩余的液体，在1147c的固相和液相之间共存。fe3% c合金随着温度的不断降低相继被转化成不同固相，由相向混合了fe3c的相转化。因此，熔融合金将从均匀相液体状态凝固成多种固相状态，在凝固过程中每种形态的转变是一步步连续地进行的。在特定温度下的每种相可以根据杠杆原理进行定量分析。相图上说明了一切相变，并给工程师们提供了宝贵的“足迹”，让他们回溯在进行逆向工程中的一部分原始经历。热力学的原理可以从理论上推测的平衡相图

17、中的相的存在。然而，它可能需要很长时间来解释相变原理。相的形成速度和机制是由动力学原理指出和解释的，动力学原理也解释了许多非平衡相变原理。各种非平衡相变图被用于许多工程应用中，通过控制温度的变化率以创建特定的非平衡相。例如，铁合金持续的冷却曲线被广泛应用于热处理工业。从逆向工程的角度来看，这些持续的冷却曲线往往比平衡相图提供更实用的信息。大多数工程合金中含有两个以上的合金元素。如果有三个组成元素，它则被称为三元体系。三元相图是一个三维空间棱镜，温度轴被垂直地建立在组成的三角基面之上，每一面代表一个元素。这是立体相图，由三个二元相图建成，每面一个二元相图。3.2.2 等效晶粒形态 最常见的三种金

18、属的微观结构晶粒形貌是等轴晶，与树突状铸件结构混合的柱状，和单晶。在等轴晶微观结构中，如图3.1a所示，在所有轴的方向上具有大致相当的尺寸。在铸件凝固过程中，柱状结构通常从寒冷的模具表面开始成形，并逐渐向内部移动，形成粗大的柱状晶粒形貌。柱状结构通常在最后会被混合在树突状铸件结构中。单晶没有相邻的形态和没有晶粒边界；整个晶体在一个晶体方向对齐。图3.3然而，这些基本晶粒的形态将通过动力学过程演变成更复杂的结构。例如，再晶粒和晶粒的变化。其他衍生的微观结构是在成形制品的具体工艺中体现出来的。例如，冷或热的图纸可以产生颗粒在一个方向上一字排开的高度定向质感的微观结构。图3.3显示了高方向的钨丝质感

19、的微观结构。在逆向工程中，复制的部分晶粒形貌至关重要的两个原因如下：首先，材料的性能和部分功能很大程度上取决于微观结构；其次，晶体的形态给制造工艺和热处理工艺提供了关键的信息。不同的热处理工艺，有不同的制造工艺呈现出不同的晶粒形貌，并具有不同的力学性能。原 文3. material characteristics and analysis material characteristics are the cornerstone for material identification and performance evaluation of a part made using reverse

20、engineering. one of the most frequently asked questions in reverse engineering is what material characteristics should be evaluated to ensure the equivalency of two materi-als. theoretically speaking, we can claim two materials are “the same” only when all their characteristics have been compared an

21、d found equivalent. this can be prohibitively expensive, and might be technically impossible. in engineering practice, when sufficient data have demonstrated that both the materials having equivalent values of relevant characteristics will usually deem having met the requirements with acceptable ris

22、k. the determination of relevant material characteristics and their equivalency requires a comprehensive understanding of the material and the functionality of the part that was made of this material. to convincingly argue which properties, ultimate tensile strength, fatigue strength, creep resistan

23、ce, or fracture toughness, are relevant material properties that need to be evaluated in a reverse engineering project, the engineer needs at least to provide the following elaboration: 1. property criticality: explain how critical this relevant property is to the parts design functionality. 2. risk

24、 assessment: explain how this relevant property will affect the part performance, and what will be the potential consequence if this material property fails to meet the design value. 3. performance assurance: explain what tests are required to show the equivalency to the original material. the prima

25、ry objective of this chapter is to discuss the material characteristics with a focus on mechanical metallurgy applicable in reverse engineering to help readers accomplish these tasks. the mechanical, metallurgical, and physical properties are the most relevant material properties to reverse engineer

26、 a mechanical part. the mechanical properties are associated with the elastic and plastic reactions that occur when force is applied. the primary mechanical properties include ultimate tensile strength, yield strength, ductility, fatigue endurance, creep resistance, and stress rupture strength. they

27、 usually reflect the relationship between stress and strain. many mechanical properties are closely related to the metallurgical and physical properties. the metallurgical properties refer to the physical and chemical characteristics of metallic elements and alloys, such as the alloy microstructure

28、and chemical composition.these characteristics are closely related to the thermodynamic and kinetic processes, and chemical reactions usually occur during these processes. the principles of thermodynamics determine whether a constituent phase in an alloy will ever be formulated from two elements whe

29、n they are mixed together. the kinetic process determines how quickly this constituent phase can be formulated. the principles of thermodynamics are used to establish the equilibrium phase diagram that helps engineers to design new alloys and interpret many metallurgical properties and reactions. it

30、 takes a very long time to reach the equilibrium condition. therefore, most grain morphologies and alloy structures depend on a kinetic process that determines reaction rate, such as grain growth rate.heat treatment is a process that is widely used to obtain the optimal mechanical properties through

31、 metallurgical reactions. it is a combination of heating and cooling operations applied to solid metallic materials to obtain proper microstructure morphology, and therefore desired properties. the most commonly applied heat treatment processes include annealing, solution heat treatment, and aging t

32、reatment. annealing is a process consisting of heating to and holding at a specified temperature for a period of time, and then slowly cooling down at a specific rate. it is used primarily to soften the metals to improve machinability, workability, and mechanical ductility. proper annealing will als

33、o increase the stability of part dimensions. the most frequently utilized annealing processes are full annealing, process annealing, isother-mal annealing, and spheroidizing. when the only purpose of annealing is for the relief of stress, the annealing process is usually referred to as stress reliev

34、ing. it reduces the internal residual stresses in a part induced by casting, quenching, normalizing, machining, cold working, or welding. solution heat treatment only applies to alloys, but not pure metals. in this process an alloy is heated to above a specific temperature and held at this temperatu

35、re for a sufficiently long period of time to allow a constituent element to dissolve into the solid solution, followed by rapid cooling to keep the constituent element in solution. consequently, this process produces a supersaturated, thermodynamically unstable state when the alloy is cooled down to

36、 a lower temperature because the solubility of the constituent element decreases with temperature. the solution heat treatment is often followed by a subsequent age treatment for precipitation hardening. from the heat treatment perspective, aging describes a time-temperature-dependent change in the

37、properties of certain alloys. it is a result of precipitation from a supersaturated solid solution. age hardening is one of the most important strengthening mechanismsfor precipitation-hardenable aluminum alloys and nickel-base superalloys.physical properties usually refer to the inherent characteri

38、stics of a material. they are independent of the chemical, metallurgical, and mechanical processes, such as the density, melting temperature, heat transfer coefficient, specific heat, and electrical conductivity. these properties are usually measured without applying any mechanical force to the mate

39、rial. these properties are crucial in many engineering applications. for example, the specific tensile strength (strength per unit weight) directly depends on alloy density, and it is more important than the absolute tensile strength when engineers design the aircraft and automobile. however, most m

40、aterial characteristics do not stand alone. they will either affect or be affected by other properties. as a result, some material properties fall into both mechanical and physical property categories, depending on their functionality, such as youngs modulus and shear modulus. an accurate youngs mod

41、ulus is usually measured by an ultrasonic technology without applying any mechanical force to the material. however, youngs modulus is also commonly referred as a ratio between the stress and strain, and they are the key elements in mechanical property evaluation. the interrelationships between meta

42、llurgical and mechanical behaviors also cause some material properties to fall into both categories, such as hardness and stress corrosion cracking resistance can be referred to as either metallurgical or mechanical properties.3.1 alloy structure equivalency 3.1.1 structure of engineering alloys eng

43、ineering alloys are metallic substances for engineering applications, and have been widely used in many industries for centuries. for example, the utilization of aluminum alloys in the aviation industry started from the beginning and continues to today; the crankcase of the wright brothers airplane

44、was made of cast aluminum alloy in 1903. alloys are composed of two or more elements that possess properties different from those of their constituents. when they are cooled from the liquid state into the solid state, most alloys will form a crystalline structure, but others will solidify without cr

45、ystallization to stay amorphous, like glass. the amorphous structure of metallic glass is a random layout of alloying elements. in contrast, a crystalline structure has a repetitive pattern based on the alloying elements. for instance, the crystalline structure of an aluminum4% copper alloy is based

46、 on the crystal structure of aluminum with copper atoms blended in. the measurable properties of an alloy such as hardness are part of its apparent character, and the underneath crystallographic structure is its distinctive generic structure. both play their respective critical roles in alloy identi

47、fication in reverse engineering. pure metallic elements, for example, aluminum, copper, or iron, usually have atoms that fit in a few symmetric patterns. the smallest repetitive unit of this atomic pattern is the unit cell. a single crystal is an aggregate of these unit cells that have the same orie

48、ntation and no grain boundary. it is essentially a single giant grain with an orderly array of atoms. this uniquecrystallographic structure gives a single crystal exceptional mechanical strength, and special applications. the single-crystal ni-base superalloy has been developed for turbine blades an

49、d vanes in modern aircraft engines. the first single-crystal-bladed aircraft engine was the pratt & whitney jt9d-7r4, which received faa certification in 1982. it powers many aircraft, such as the boeing 767 and the airbus a310. compared to the counterpart with equiaxed grains, a single-crystal jet

50、engine turbine airfoil can have multiple times better corrosion resistance, and much better creep strength and thermal fatigue resistance. most engineering alloys, however, have a multigrain morphology. the grain size and its texture have profound effects on alloy properties. fine grain engineering

51、alloys usually have higher tensile strength at ambient temperature. however, for high-temperature applications, coarse grain alloys are preferred due to their better creep resistance. the effects of microstructure on the properties of engineering alloys will be discussed in detail later.3.1.2 effect

52、s of process and product form on material equivalency the part features, distinctive microstructure in particular, resulted from dif- ferent manufacturing processes, and product forms thereby produced from raw materials are the characteristics widely used to identify material equivalency in reverse

53、engineering. conventional manufacturing processes used on engineering alloys to produce a specific product form include casting, forging, and rolling, as well as other hot and cold work. power metallurgy, rapid solidification, chemical vapor deposition, and many other special processes, for example,

54、 osprey spray forming and superplastic forming, are also used in industries for specific applications. some near-net-shape processes directly shape the alloy into the near-final product form or complex geometry. in comparison to traditional cast and wrought products with multiple processing steps, a

55、 simpler conversion from raw material to the final product that involves fewer steps is often more desirable. for example, the osprey spray forming process first atomizes a molten alloy, which is then sprayed onto a rotating mendrel to form a ring-shape preform hardware like an engine turbine case o

56、r seal. the near-net-shape preform is subsequently made into the final product using a hot isostatic press. an osprey sprayformed ni-base superalloy product is more cost effective, and typically has an average grain size of about 65 m. it shows a similar microstructure and comparable properties to a

57、 wrought piece with the same alloy composition, and has better properties than a cast product. recent advances in manufacturing technologies have also produced alloys with nano-microstructure. the mechanical properties of engineering alloys are primarily determined by two factors: composition and microstructure. though the alloy composition is intrinsic by design, the microstructure evolves during manufacturing. the microstructure and consequently the mechanical properties of an eng