武汉理工大学研究生--材料科技英语-课文翻译(3)

Ferritic stainless steels contain 12 to 18% chromium and very little carbon. Austenitic stainless steels containenough nickel so that they have a fcc crystal structure at all temperatures below melting. They are more expensivethan ferritic stainless steels and are nonmagnetic. The third main class of stainless steels is martensitic. Martensiticstainless steels have compositions similar to ferritic stainless steels, but with enough carbon so that when heated theytransform to austenite. The hardenability is so high that they form martensite even with slow cooling.

铁素体不锈钢含有12～18%的铬和极少的碳。奥氏体不锈钢中含有足够的镍，使其在低于熔点的所有温度下都具有fcc晶体结构。它们比铁素体不锈钢更贵，并且是非磁性的。第三类不锈钢是马氏体。马氏体不锈钢具有类似于铁素体不锈钢的组成，但含有足够的碳，使得当加热时它们转变为奥氏体。可淬性如此之高，即使在缓慢冷却下也能形成马氏体。

Austenitic stainless steels are significantly more complex in nature than the ferritics and martensitics in that theyhave at least two major alloying elements: chromium and nickel. Austenitic stainless steels have a strong tendency towork harden. The energy of deformation promotes the transformation of the metastable austenite to martensite.Austenitic stainless steels are incontrovertibly austenitic in most commercial forms. The austenite structure is broughtabout by nickel additions or in some cases by nickel and manganese additions. Manganese is also an austenitizer.

奥氏体不锈钢在本质上比铁素体和马氏体显着更复杂，因为它们具有至少两种主要的合金元素：铬和镍。奥氏体不锈钢有较强的可加工性，它的变形能力促进了亚稳态的奥氏体向马氏

体的转变。奥氏体不锈钢在大多数的商业形式中无疑是奥氏体。奥氏体结构是由添加镍元素或在某些情况下添加镍和锰元素带来的。锰也是奥氏体。

Property

We can consider the properties of a material in two categories—mechanical and physical.

The mechanical properties describe how the material responds to an applied force or stress. Stress is defined asthe force divided by the cross-sectional area on which the force acts. The most common mechanical properties are thestrength, ductility, and stiffness of the material. However, we are often interested in how the material behaves when itis exposed to a sudden intense blow (impact), continually cycled through an alternating force (fatigue), exposed tohigh temperatures (stability), or subjected to abrasive conditions (wear). The mechanical properties not only determinehow well the material performs in service, but also determine the ease with which the material can be formed into auseful shape. A metal part formed by forging must withstand the rapid application of a force without breaking andhave a high enough ductility to deform to the proper shape. Often small changes in the structure have a profoundeffect on the mechanical properties of the material.

我们可以将材料的性质分为两类-力学性能和物理性能。 力学性能描述材料如何对施加的力或应力作出反应。应力定义为单位横截面积的力。最常见的机械性能是材料的强度，延展性和刚度。然而，我们经常感兴趣的是当材料受到突然强烈的撞击（冲击），受到交变力作用（疲劳），受到高温作用（稳定性）或受磨料磨损（磨损）等影响时如何反应。力学性能不仅决定了材料在使用中的性能，而且决定了材料能否形成有用的形状。通过锻造形成的金属部件必须承受力的快速施加而不破裂并且具有足够高的延展性使其能改变为适当的形状。通常，结构的细微变化对材料的机械性能具有深远的影响。

Physical properties include electrical, magnetic, optical, thermal, elastic, and chemical behavior. The physicalproperties depend both on structure and processing of the material. Even tiny changes in the composition cause aprofound change in the electrical conductivity of many semiconducting metals and ceramics.

物理性质包括电，磁，光，热，弹性和化学行为。物理性质都取决于材料的结构和加工。甚至成分的微小变化也会导致许多半导体金属和陶瓷的导电性的深奥变化。

High firing temperatures may greatly reduce the thermal insulation characteristics of ceramic brick. Smallamounts of impurities change the color of a glass or polymer.

高烧结温度可大大降低陶瓷砖的隔热特性。少量杂质会改变玻璃或聚合物的颜色。

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