An alloy is a mixture or metallic solid solution composed of two or more elements. An alloy will contain one or more of the three: a solid solution of the elements (a single phase); a mixture of metallic phases (two or more solutions); an intermetallic compound with no distinct boundary between the phases. Solid solution alloys give a single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on the thermal (heat treatment) history of the material. An intermetallic compound will have another alloy or pure metal embedded within another pure metal. Alloys are used as their properties are superior to those of the pure component elements.