考试复习笔记-材料概论(上)

Chromium additions produce stainless steels for corrosion resistance .
加入铬添加剂可以生产耐腐蚀的不锈钢。
Additions such as tungsten lead to high-hardness alloy used as tool steels .
加入钨之类的添加剂可以生产用做工具刚的高硬度合金。
superalloys include many stainless steels that combine corrosion resistance with high strength at elevated temperatures .
超合金包括多种不锈钢，这些不锈钢在高温下即耐腐蚀同时又具有高强度。
超过90%重量的工程材料是铁基合金，包括刚（含0.05～2.0 wt% C）和铸铁（含2.0～4.5 wt% C）。
Most steels involve a minimum of alloy additions to maintain moderate costs .
大多数的刚只含有少量的合金添加剂使材料的成本适中。
要理解这各种材料的性能需要从微观或亚微观尺度上研究材料的结构。
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The relative ductility of certain metal alloys is related to atomic-scale "architecture".
某些金属合金的延展性的相对大小与其原子尺度上的“构造有关。
当我们了解了材料的性能，材料的实际选择就可以在两个层次上进行。
First ,there is competition among the various categories of materials .
首先，在材料的各种类之间存在竞争。
Second ,there is competition within the most appropriate category for the optimum ,specified material .
白铁和灰铁是典型的脆性材料，而软铁和可锻铁的特征是其良好的延展性。
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Nonferrous alloys include a wide range of materials with individual attributes .
非铁合金包括很多种材料，这些材料具有各自性能特性。
Aluminium ,magnesium ,and titanium alloys have found wide use as lightweight structure members .
通过拉伸实验可以获得最基本的设计数据，包括弹性模量、屈服强度、拉伸强度、延展性和韧性。
Closely related elastic properties are Poisson's ratio and the shear modulus .
与弹性密切相关的是泊松比和剪切模量。
The hardness test is asimple alternative to the tensile test that provides an indication of alloy strength .
硬度试验是拉伸试验的简单替代方法，可以获得合金强度方面的指示。
The impact test provides a measure of energy to fracture and correlates with toughness as determined by tensile testing .
The first four categories comprise the structural materials .
前四类材料构成了结构材料。
The fifth type (semiconductor) is a separate category of clectronic materials distinguished by its unique ,intermediate electrical conductivity.
可以被工程师使用的材料的范围很广泛，这些材料可以划分为5类：金属、陶瓷（玻璃）、聚合物、复合材料和半导体材料。
The first three categories can be associated with distinct tyres of atomic bending .
前三类材料的分类与他们独特的化学键的类型相关。
通过冲击实验可以进行断裂能的测量，而且该实验与韧性相关，类似于通过拉伸实验进行的测量。
A special consideration of this test is the ductile-to-brittle transition temperature for bcc alloys such as structural steels .
Virtually every major property of the five materials' categories just outlined will be shown to result directly from mechanisms occurring at either the atomic or the microscopic scale .
These are plain-carbon or low-alloy (＜5 wt% total noncarbon additions) steels .
这些钢是普碳钢或低合金钢（非碳添加剂的总加入量＜5 wt%）
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Special care in alloy selection and processing can result in high-strength low-alloy (HSLA) steels .
对合金选择和加工处理的特别关注导致了高强度低合金钢的出现。
For demanding design specifications high-alloy (＞5 wt% total noncarbon additions ) steels are required .
对于要求苛刻的设计师需要高合金刚（非碳添加剂的总加入量＞5 wt%）来满足要求。
其次，在合适的材料种类中还存在究竟哪种材料最适合的竞争。
In addition ,new developments can lead to the rejection of an alternate material for a given design .
另外，对于某些特定的设计，新研制出来的材料还带来替代材料选择的问题。
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To understand the properties of engineering materials ,it is necessary to understand their structure on the atomic and microscopic scale .
为了理解工程材料的性能，必须理解它们在原子尺度和微观尺度上的结构。
铜合金和镍合金因其良好的耐化学和高温性能以及在电子和磁性材料方面的应用而具有特别的吸引力。
Other important nonferrous alloys include the zinc and lead and the refractory and precious metals .
其他重要的非铁合金包括锌合金、铝合金以及高温合金和贵金属。
Over 90% by weight of the materials used for engineering are iron-based or ferrous allows ,which include the steels (containing 0.05 to 2.0 wt% C) and the cart irons (with 2.0 to 4.5 wt% C).
The cast irons exhibit a wide range of behavior depending on composition and processing history .
铸铁的性能变化比较大，这取决于其化学组成和加工处理过程。
White and gray irons are typically brittle ,whereas ductile and malleable irons are characteristically ductile .
实际上，前面列出的五类材料中每一种材料的主要性能都直接取决于它们发生在原子或微观尺度上的机制。
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Metals play amajor sole in engineering design ,especially as structural element.
在工程设计中，金属材料起主要作用，特别是对于结构组元的设计更是如此。
铝合金、镁合金和钛合金作为轻质结构材料而得到广泛应用。
Copper and nickel alloys are especial attractive for chemical and temperature resistance and electrical and magnetic applications .
Similarly ,the development of transparent ceramics has required careful control of microscopic-scale "architecture".
与此类似，透明陶瓷的研制也需要严格控制其微观尺度上的“构造”。