Alloys:

An alloy is a mixture of two or more materials, at least one of that is a metal.  Alloys could have a microstructure consisting of solid solutions, whereas secondary atoms are introduced as substitutionals or interstitials in a crystal lattice. An alloy might also be a crystal along with a metallic compound at each lattice point. In addition, alloys may be composed of secondary crystals imbedded in a main polycrystalline matrix. That category of alloy is known as a composite (by the term "composite" does not essential imply in which the component materials are metals).  Discusses how various elements change the physical properties of a metal.