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。
1、
The wide range of materials available to engineers can be divided into five categories :metals ,ceramics and glasses ,polymers ,composites ,and semiconductors .
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。
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。
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.
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 .
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。
2、
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。
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 .
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 .
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。
3、
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。
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 .
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。
4、
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。
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).
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。
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%）
5、
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。
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。
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 .
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。
6、
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 structu
re members .
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 .
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。
7、
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 .
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 .
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 .
对于这个实验需要特别考虑的是bcc 结构的合金（如结构钢）的延展性-脆性转变温度。
8、
Fracture toughness testing measures the stress intensification caused by a crack responsible for the catastrophic failure of the alloy .
断裂韧性实验测量的是由裂纹引起的应力集中情况，这些裂纹可能会引起合金的灾难性破坏。
This is a microscopic statement of tendency toward brittleness or ductility .
这个实验是对材料的脆性或延展性趋势的微观描述。
Fatigue testing demonstrates that the failure stress of an alloy drops off dramatically with prolonged cyclic loading .
疲劳实验表明，合金破坏应力随循环载荷的延展而显著下降。
The creep test indicates that above a temperature of about one-half time the absolute melting point ,an alloy has sufficient atomic mobility to deform plastically at stresses below the room-temperature yield stress .
蠕变实验表明，在材料的绝对熔点一半以上的温度下，合金的原子具有足够的迁移能力而使得合金在低于室温屈服应力的条件下发生塑性形变。
9、
Steel generally contains between 0.05 and 2.0 wt% C .
钢一般还有0.05～2.0%的
C。
The cast iron generally contain between 2.0 and 4.5 wt% C .
铸铁一般含有2.0～4.5%的C。
Within the steel category ,we shall distinguish whether or not a significant amount of allowing elements other than carbon is used .
在钢这类材料中，必须清楚它是否使用了显著含量的非碳合金元素。
A composition of 5 wt% total noncarbon additions will serve as an arbitrary boundary between low-alloy and high-alloy steels .
在化学组成中总量5%的非碳添加剂是人为设定的低合金钢和高合金钢的划分界限。
These alloy additions are chosen carefully because they invariably bring with them sharply increased material costs .
这些合金添加剂的选择是谨慎的，因为他们的加入总是会显著增加材料成本。
They are justified only by essential improvements in properties such as higher strength or improved corrosion resistance .
只有确实能够改进材料的性能，如提高材料强度或改善材料的耐腐蚀性，这些添加剂的加入才能是正确的。
10、
Ceramics and glasses represent a diverse family of engineering materials.
陶瓷与玻璃代表的是品种繁多的一个工程材料体系。
The term ceramics is associated with predominantly crystalline materials .
陶瓷主要是指多晶材料。
Silicates are abundant and economical examples finding uses in numerous consumer and industrial products .
硅酸盐材料的原料资源丰富且成本低廉，在各个领域中获得广泛应用。
Nonsilicate oxides such as MgO are widely used in such areas as refractories ,nuclear fuels ,and electronic material .
非硅酸盐氧化物材料，如MgO，广泛应用与耐火材料、核燃料以及电子材料领域。
Partially stabilised zirconia (PSZ) is aprimary candidate for high-temperature engine components .
部分稳定的氧化锆PSZ 材料是高温发动机部件的首选替代品。
Nonoxide ceramics include silicon nitride another candidate for engine components .
非氧化物陶瓷还包括氧化硅，这是发动机部件的另一个替代品。
11、
Glasses are noncrystalline solids chemically similar to the crystalline ceramics.
玻璃是在化学组成上与多晶陶瓷相似的非晶固体材料。
The predominant category is the silicates,which include materials from the expensive,high-temperature vitreous silica to common soda lime silica window glass.
玻璃中最重要的是硅酸盐玻璃，从昂贵的高温石英玻璃，到普通的钠钙硅酸盐窗玻璃。
Protective and decorative glass coating on ceramics and metals are termed glazes amdenamels,respectively.
陶瓷和金属表面的保护性和装饰性的玻璃质涂层分别被称为釉和搪瓷。
Many silicate glasses contain substantial amount of other oxide component,although there is little commercial use for completely nonsilicate oxide glasses.
许多硅酸盐玻璃含有相当量的其它氧化物组分，尽管完全的非硅酸盐氧
化物玻璃的商业应用价值不大。
Some nonoxide glasses have found commercial users(chalcogenide glasses and amorphous semiconductors)
有些非氧化物玻璃已经找到了商业应用（如硫族玻璃用于无定形半导体材料）。
12、
The glass-ceramics are distinctive products that are initially processed as glasses and then carefully crystallized to form a dense , fine-grained ceramic product with excellent mechanical and thermal shock resistance .
玻璃陶瓷是一种很独特的产品，它首先是被加工成玻璃，然后通过严格的控制使它析晶而成为致密细晶的析晶产品，具有优越的力学和抗热震性能。
Most commercial glass-ceramics are in the Li2O-Al2O3-SiO2 system , which is characterized by compounds with exceptionally low thermal expansion coefficients .
应用最多的是 系玻璃陶瓷，其特点是具有特别低的热膨胀系数。
13、
Several mechanical properties play important roles in the structural applications and processing of
ceramics and glasses .
在陶瓷与玻璃的作为结构应用极其加工处理过程中，力学性能起重要的作用。
Both ceramics and glasses are characterized by brittle fracture
陶瓷和玻璃的特征都是脆性断裂。
The low values of fracture toughness of traditional ceramics correlate with low tensile strength , although compressive strength are relatively high .
传统陶瓷的断裂韧性很低，这与其拉伸强度低有关，尽管其抗压强度很高。
A major area of research and development for structure ceramics is in the significant increase of fracture toughness .
对结构陶瓷进行研究与开发的主要领域是显著增加其断裂韧性。
Transformation toughness PSZ is a prime example .
相变增韧PSZ就是很好的例子。
14、
In contract to metal , 26726 and glasses demonstrate a statistic fatigue mechanism due to chemical attack by atmosphere moisture around room temperature .
与金属相比，陶瓷与玻璃具有静态疲劳机制，这是由于室温下大气水分的化学腐蚀造成的。
Creep plays an important role in the application of coral in the high temperature service .
对于陶瓷在高温条件下的应用，瑞变起重要的作用。
Diffusional mechanisms combine with grain boundary sliding to provide the possibility of extensive deformation.
扩散机制再加上晶界滑移使得材料具有很大的可变形性。
The inherent brittleness of ceramics and glasses combined with thermal expansion mismatch or low thermal conduct can lead to thermal shock .
陶瓷和玻璃固有的脆性再加上热膨胀失配或低的热传导率导致材料的热震破坏。
15、
Below the glass transition temperature(Tg) , glasses deform by an elastic mechanism .
在玻璃转变温度（Tg）以下，玻璃通过弹性机制发生变形。
Above Tg they deform by a viscous flow mechanism .
在Tg温度以上，玻璃通过粘
性流动机制发生变形。
The exponential change of viscosity with temperature provides a guided for routine processing of glass products as well as the development of fracture resistant tempest glass .
粘度随温度而指数变化这一特征为玻璃产品的一般加工处理和抗脆断的钢化玻璃的研制提供了指导方针。
16、
The wide use of ceramics and , especially , glasses for optical applications make a knowledge of optical properties important .
陶瓷材料的广泛应用，特别是玻璃在光学方面的应用，使得材料的光学性能非常重要。
The refractive index (n) has a strong effect on the subjective appearance of transparent solid or coating , and n is related to the reflectance of the surface through fresnel formula .
折射率（n）对于透明固体材料或涂层的外观具有重要的影响，并且n通过fresnel公式而与表面反射相关。
Surface roughness determine the relative amount of speculate and diffuse reflection .
表面粗糙度决定镜面反射和漫反射的量的相对大小。
Transparency is limited by the mature of second phase pores or particle , which serve as scatter centers .
透明度受到材料中的气孔或颗粒等作为散射中心的第二相的性质的限制。
Color is produced by the selective absorption of certain wavelength range in the visible light spectrum .
颜色是由于材料对可见光谱中一定波长的光进行选择性吸收而产生。
17、
Having second phase particles of tetragonal zirconia in a matrix of cubic zirconia is the key to improved .
在立方氧化锆的基质中含有第二相四方氧化锆的颗粒，这是材料韧性改善的关键。
A propagating crack create a local stress field that induce a transformation of zirconia particle to the monoclinic structure in that vicinity .
扩展裂纹产生一个局部应立场，进而在该区域引起四方氧化锆颗粒向单斜结构的相变。
The slightly larger specific volume of the monoclinic phase cause an effective compressive load locally and , in turn , the squeeze of the crack shut .
单斜相相对稍大的单位体积产生一个有效的局部压缩载荷，反过来，通过”挤压”作用使裂纹闭合。
18、
Microcracks purposely introduced during process of the ceramics are available to blunt the tip of an advance crack .
在陶瓷加工过程中有目的的引入微裂纹能够钝化扩展裂纹的尖端。
The Griffith expression indicate that the larger tip radius can dramatically reduce the local stress at the crack tip .
Griffith公式表明，裂纹尖端半径的增大可以显著降低裂纹尖端的局部应力。
19、
The glass is first equilibrium above the glass transition temperature Tg ,followed by a surface quench that forms a rigid surface skin at a temperature below Tg .
首先，在玻璃转变温度Tg以上，玻璃达到平衡态，然后，对玻璃进行表面急冷，至Tg
温度以下，则在玻璃表面形成刚硬的表面层。
Because the interior is still above Tg .interior compress stress are largely relaxed ., although a modest tensile stress is present in the surface "skin".
由于玻璃内部依然在Tg温度以上，内部的压应力被大量释放，尽管有一个适度的张应力存在于玻璃表层。
Slow cooling to room temperature allows the interior to contract considerably more than the surface , causing a net compressive residual stress on the surface .
慢速冷却到室温后，玻璃内部发生的收缩显著大于表面层，在玻璃表层产生一个残余的压应力，
Balanced by a smaller tensile residual stress in the interior .
该压应力被玻璃内部的较小残余应力所平衡。
This is an ideal situation for a brittle ceramics .
对于脆性材料来说，这是一种很理想的状况。
20、
The microscopic mechanism of scatter is the scattering of light by small second phase pores or particle .
散射的微观机制是可见光被小的气孔、颗粒等第二相散射。
The degree of opacification caused by the pores or particle depend on their average size and concentration as well as mismatch of indices of refractive .
由气孔过颗粒所产生的乳浊度取决于它们的平均颗粒尺寸和分布浓度以及折射率的失配。
If individual pores or particle are significantly smaller than the wavelength of light （400～700nm ）, they are ineffective scattering centers .
如果单个气孔或颗粒小于可见光的波长（400～700纳米），它们就是无效的散射中心。
The scattering effect is maximized by pores or particle sizes within the range of 400～700nm.
当气孔或颗粒尺寸在400～700纳米范围内时，散射效果最好。