专业外语英语加汉语Unit1MaterialsScienceandEngineering.doc

Unit1Materials Science and EngineeringMaterials are properly more deep-seated in our culture than most of us realize. 材料可能比我们大部分人所意识到的更加深入地存在于我们的文化当中。Transportation, housing, clothing, communication, recreation and food productionvirtually every segment of our lives is influenced to one degree or another by materials.运输、住房、衣饰、通讯、娱乐，还有食品生产实际上我们日常生活的每个部分都或多或少地受到材料的影响。Historically, the development and advancement of societies have been intimately tied to the members abilities to produce and manipulate materials to fill their needs. 从历史上看，社会的发展和进步已经与社会成员生产和利用材料来满足自身需求的能力紧密地联系在一起。In fact, early civilizations have been designated by the level of their materials development.事实上，早期文明是以当时材料的发展水平来命名的。（也就是石器时代，青铜器时代）The earliest humans has access to only a very limited number of materials, those that occur naturally stone, wood, clay, skins, and so on. 最早的人类只能利用非常有限数量的材料，象那些自然界的石头，木头，黏土和毛皮等等。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. 随着时间的推延，人类发现了性能优于自然材料的制造新材料的技术：这些新材料包括陶器，各种金属。Furthermore, it was discovered that the properties of a material could be altered by heat treatments and by the addition of other substances. 而且，人类发现通过对这些材料进行热处理和添加新的元素可以改变材料的性能。At this point, materials utilization was totally a selection process, that is, deciding from a given, rather limited set of materials the one that was best suited for an application by virtue of its characteristic. 从这一点来说，材料利用完全地是一个选择过程，也就是说，在给定的相当有些限的一批材料中根据材料的特性,为某种具体的应用选择最适合的材料。It was not until relatively recent times that scientists came to understand the relationships between the structural elements of materials and their properties.直到前不久的一段时间里，科学家们才开始了解材料的组成元素与其性质之间的关系。This knowledge, acquired in the past 60 years or so, has empowered them to fashion, to a large degree, the characteristics of materials.这个在过去60年左右的时间里得到的结论已经促使科学家们更广泛地运用材料的这些特性。Thus, tens of thousands of different materials have evolved with rather, 因此，数以万计的具有专门特性的不同材料应运而生。specialized characteristics that meet the needs of our modern and complex society.它们满足了现代复杂社会的需要.The development of many technologies that make our existence so comfortable has been intimately associated with the accessibility of suitable materials. 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 possible without the availability of inexpensive steel or some other comparable substitutes. In our contemporary era, sophisticated electronic devices rely on components that are made from what are called semiconducting materials.许多使我们的生活如此舒适的技术的发展都 与（人类）能够获得合适的材料密切相关。往往对一种材料类型的理解的进步会成为某一技术发展历程的第一步。 比方说，没有那些廉价的钢铁或其他类似的代用品，就不可能有汽车。在我国当代，一些精密电子仪器就依赖于那些由我们称做半导体材料制作而成的零部件。Materials Science and Engineering Materials science is an interdisciplinary study that combines chemistry, physics, metallurgy, engineering and very recently life sciences. One aspect of materials science involves studying and designing materials to make them useful and reliable in the service of human-kind. 材料科学是一门结合了化学，物理，冶金，工程以及最近结合的生命科学的跨专业研究科学。材料科学研究的一个方面是研究开发服务于人类使用的可靠的材料。It strives for basic understanding of how structures and processes on the atomic scale result in the properties and functions familiar at the engineering level. 它力争对原子层次上物质的结构及加工对我们熟悉的工程上材料的性能和功能的影响有一个基本的认识。Materials scientists are interested in physical and chemical phenomena acting across large magnitudes of space and time scales. 材料科学家们感兴趣的是大跨度空间与时间上发生的物理化学现象。In this regard it differs from physics or chemistry where the emphasis is more on explaining the properties of pure substances. 在这一点，它不同于把重点更多的放在解释纯粹物质特征现象的物理和化学专业。 In materials science there is also an emphasis on developing and using knowledge to understand how the properties of materials can be controllably designed by the varying the compositions, structures, and the way in which the bulk and surfaces phase materials are processed. 材料科学还有一个重点是发展使用知识来了解如何通过更改材料的成分，结构和大量表面相材料的处理方法来控制设计材料的性能。In contrast, materials engineering is, on the basis of those structure properties correlations, designing or engineering the structure of a material to produce a predetermined set of properties. 相反，材料工程是在（材料）结构和性能相互联系的基础上，设计策划一种材料的结构来实现一系列预知的性能。In other words, material engineering mainly deals with the use of materials in design and how materials are manufactured.换句话讲，材料工程主要涉及材料设计方面的用途和生产方案的问题。“structure” is a nebulous term that deserves some explanation. “结构”是一个应当予以解释的模糊概念。In brief, the structure of a material usually relates to the arrangement of its internal components. 简言之，一种材料的结构通常与其内部成分的排列有关。Subatomic structure involves electrons within the individual atoms and interactions with their nuclei. 亚原子结构包括单个原子内部的电子以及它们和原子核之间的相互作用。On anatomic level, structure encompasses the organization of atoms or molecules relative to another. The next large structural realm, which contains large groups of atoms that are normally agglomerated together, is termed “microscopic” meaning that which is subject to direct observation using some type of microscope.在原子水平上，结构包括与另外的原子或分子相对的原子或分子的组织，更高层次的结构领域包含我们称作“微观的”结构，该结构是凝聚成一团的使用某种显微镜才能直接观察的原子群（簇，团）。 Finally, structural elements that may be, viewed with naked eye are termed “macroscopic”.最后，可直接用肉眼观察到的结构要素被称为“宏观型”。The notion of “property” deserves elaboration. 性能的概念需要特别解释一下。While in service use, all materials are exposed to external stimuli that evoke some type of response. For example, a specimen subject to forces will experience deformation; or a polished metal surface will reflect light. 在应用中，所有的材料受到外部刺激会产生某种反应。比如：样本材料受到压力会产生变形，光滑金属表面会反光。 Property is a material trait in terms of the kind and magnitude of response to a specific imposed stimulus. 性能是一种材料的特性，它由特殊的刺激所引起的反应的种类和大小决定。Generally, definitions of properties are made independent of material shape and size. 一般来说，性能的定义与材料本身的形状和大小无关。Virtually all important properties of solid Material may be grouped into six different categories: mechanical, electrical, thermal, magnetic, optical, and deteriorative. 事实上，所有固体材料的重要性能可以分为6个不同的类别：机械性能、电学性能、热学性能、磁性、光学性能以及腐蚀性。For each there is a characteristic type of stimulus capable of provoking different responses. 对于每一种性能都有一种特殊类型的激励源能够引起不同的反应。 Mechanical properties relate deformation to an applied load or force: examples include elastic modulus and strength. 机械性能是关于对外加载荷和外加力的变形，比如：弹性模量和弹性强度。For electrical properties, such as electrical conductivity and dielectric constant, the stimulus is an electric filed. 对于力学性能，有电导率和介电常数，它的激励源是一个电场。 The thermal behavior of solids can be represented in terms of heat capacity and thermal conductivity. 固体的热学性能可以用热容和热导率来表示。 Magnetic properties demonstrate the response of a material to the application of a magnetic field. 磁性表明了材料对外加磁场的反应。For optical properties, the stimulus is electromagnetic or light radiation: index of refraction and reflectivity are representative optical properties. 对于光学性能，激励源是电磁场或是光辐射。折射率和反射率便代表了这种光学性能。 Finally, deteriorative characteristics indicate the chemical reactivity of materials. 最后，腐蚀性则指示了材料的化学反应。In addition to structure and properties, two other important components are involved in the science and engineering of materials, namely “processing” and “performance”.除了结构和性质以外,还有两个重要的因素也是材料科学与工程要考虑的,那就是“加工”和“使用性能”With regard to the relationships of these four components, the structure of a material will depend on how it is processed. Furthermore, a materials performance will be a function of its properties. Thus, the interrelationship between processing, structure, properties, and performance is linear as follows:就这四个方面的关系来说，材料的结构取决于它的加工方法。进一步说，材料的使用性能是加工结构性能使用性能性质的表现。因此，热处理、结构、性质、性能之间的关系可以列出如下：Processing-Structure-Properties-Performance Why Study Materials Science and EngineeringWhy do we study materials? 为什么我们要学习材料科学呢？Many an applied scientists or engineers, whether mechanical, civil, chemical, or electrical, will be exposed to a design problem involving materials at one time or another. 许多应用科学家和工程师，无论机械，民事，化学，或者电气方面，在某些情况下都遇到涉及材料的设计问题Examples might include a transmission gear, the superstructure for a building, an oil refinery component, or an integrated circuit chip. 实例有传动装置，建筑顶层结构，炼油的零部件或集成电路板。 Of course, materials scientists and engineers are specialists who are totally involved in the investigation and design of materials. 当然，材料科学家和工程师是在材料的研究和设计中全程参与的专家。 Many times, a materials problem is to select the right material from many thousands available ones. 许多时候,材料学的一个问题是从成千上万种材料中选出最合适的那一种.There are several criteria on which the final decision is normally based. 作出最后的决定往往需要依据几项准则. First of all, the in-service conditions must be characterized. 首先,必须确定适用的条件. On only rare occasion does a material possess the maximum or ideal combination of properties. 只有在很少的情况下,一种材料才拥有最大或理想的综合性能.Thus, it may be necessary to tradeoff one characteristic for another. 所以,有必要把它的一种性能替换成另一种.The classic example involves strength and ductility.；normally, a material having a high strength will have a only limited ductility. 有一个经典的例子是涉及强度和延展性的,正常的情况下,有很高的强度的材料仅有有限的延展性. In such cases a reasonable compromise between two or more properties may be necessary. 在这些情况下,两种或两种以上性能之间的合理折衷是很有必要的。 A second selection consideration is any deterioration of ma