Perhaps the most common classifying distinction among engineering materials is whether the material is metallic or nonmetallic. The common metallic include iron, copper, aluminium, magnesium, nickel, titanium, lead, tin, zinc, as well as the alloy of these metals, such as steel, brass, and bronze.
They posses the metalic properties of luster, high thermal conductivity, and high electrical conductivity. They are relatively ductile and some have good magnetic properties. Some common nonmetal are wood, brick, concrete, glass, rubber, and plastic. Their properties very widely, but they generally tend to be less ductile, weaker, and less dense thn the metals and have poor electrical and thermal conductivities.
Although metals have traditionally been the more important of the two groups, the nonmetallic group has made great strides and new nonmetallic materials are continuosly being developed. Advanced ceramics, composite materials, and engineered plastic are receiving considerable attention. In many case, metals and nonmetal are viewed as competing materials, with selection being based on how well each is capable of providing the required properties. Where both perform adequately ,total cost often becomes the deciding factor, where total cost includes both the cost of the material and the cost of fabricating the desired component.
Reference : DeGarmo, Paul.2002.Materials and processes in manufacturing
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