Tham khảo tài liệu 'material science_ vol 1 of 2 - us doe (1993) ww part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Structure of Metals DOE-HDBK-1017 1-93 ALLOYS ALLOYS Most of the materials used in structural engineering or component fabrication are metals. Alloying is a common practice because metallic bonds allow joining of different types of metals. EO DEFINE the term alloy. EO DESCRIBE an alloy as to the three possible microstructures and the two general characteristics as compared to pure metals. EO IDENTIFY the two desirable properties of type 304 stainless steel. Alloys An alloy is a mixture of two or more materials at least one of which is a metal. Alloys can have a microstructure consisting of solid solutions where secondary atoms are introduced as substitutionals or interstitials discussed further in the next chapter and Module 5 Plant Materials in a crystal lattice. An alloy might also be a crystal with a metallic compound at each lattice point. In addition alloys may be composed of secondary crystals imbedded in a primary polycrystalline matrix. This type of alloy is called a composite although the term composite does not necessarily imply that the component materials are metals . Module 2 Properties of Metals discusses how different elements change the physical properties of a metal. Common Characteristics of Alloys Alloys are usually stronger than pure metals although they generally offer reduced electrical and thermal conductivity. Strength is the most important criterion by which many structural materials are judged. Therefore alloys are used for engineering construction. Steel probably the most common structural metal is a good example of an alloy. It is an alloy of iron and carbon with other elements to give it certain desirable properties. As mentioned in the previous chapter it is sometimes possible for a material to be composed of several solid phases. The strengths of these materials are enhanced by allowing a solid structure to become a form composed of two interspersed phases. When the material in question is an alloy it is possible to .
