METALS AND ALLOYS

The electrons in a metallic lattice are in a "gas," form, therefore the core electrons and nuclei determine the structure in metals. This will be true of most solids we will describe, regardless of the type of bonding, since the electrons occupy such a small volume compared to the nucleus.

STRUCTURE OF METALS AND ALLOYS

Most metals and alloys crystallize in one of three very common structures: body-centered cubic (bcc), hexagonal close packed (hcp), or cubic close packed (ccp, also called face centered cubic, fcc).

Defects

The crystals structure is not always perfect and in many structures there are some defects (imperfection) .There are several different kinds of defects that can be found in metallic crystals. Non-directional bonding has an important impact on the mechanical properties of metals. Because there is no strong preference for one atomic position over another, the structure is not greatly impaired by the vacancy of a single atom or the dislocation of a group of atoms. These "mistakes" in packing of metal atoms within crystals are called defects. The deformability of metals is the direct result of defects in the crystal structure.

Alloys

An alloy is a mixture of metals or a mixture of a metal and another element. Alloys are defined by metallic bonding character. An alloy may be a solid solution of metal elements (a single phase) or a mixture of metallic phases (two or more solutions). Alloys are used in a wide variety of applications. In some cases, a combination of metals may reduce the overall cost of the material while preserving important properties. In other cases, the combinations of metals represent improving of properties to the constituent metal elements such as corrosion resistance or mechanical strength. Examples such as Fe –Cr, Cu –Al…

In this topic will be the physical and mechanical properties of Ferrous and Nonferrous metals such as Cu, Al, Fe, Pb &Zn discuss