济南大学材料概论(上)

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 .
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。
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The wide use of metals as structural elements lead us to concentrate on their mechanical properties .
金属材料作为结构组元的广泛应用使得我们特别关注其力学性能。
The tensile test gives the most basic design data including modulus of elasticity ,yield strength ,tensile strength ,ductility ,and toughness .
The fourth category (composites) involves combination of two or more materials from the previous three categories .
第四类材料（复合材料）是由前三类材料中的2种或2种以上的材料复合而成。
材料作为结构组分得到广泛使用，这使我们更加关注这些材料的机械性能。我们从拉伸试验中获知材料最基本的设计数据，这些数据包括弹性模量、屈服强度、拉伸强度、延展性和韧性。泊松比和剪切模量与材料的弹性性质密切相关。弹性形变最基本的机制是原子键的滑移。在晶体材料的塑性变形过程中，位错起着关键作用，它在原子最紧密堆积面上沿着原子最紧密堆积方向运动使原子发生取代。
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 .
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 .
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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。
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 .
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 .
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.
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The wide range of materials available to engineers can be divided into five categories :metals ,ceramics and glasses ,polymers ,composites ,and semiconductors .
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).
第五类材料（半导体材料）是单独的一类材料，即电子材料，它与其他材料的显著区别是其独特的中等大小的导电能力。
Understanding the properties of these various material requires examination of structure at either amicroscopic or submicroscopic scale .
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”。
Once the properties of material are understood ,the practical selection of materials is done at two levels .
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。
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。
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。
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 .
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 .
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 .