A mixture of two or more metals is called an alloy. Alloys are distinguished from composite metals in that alloys are thoroughly mixed, creating, in effect, a synthetic metal. In metal composites, the introduced metal retains its identity within the matrix in the form of fibers, beads, or other shapes. Alloys can be created by mixing the metals while in a molten state or by bonding metal powders. Various alloys have different desired properties such as strength, visual attractiveness, or malleability. The number of possible alloy combinations is almost endless since any metal can be alloyed in pairs or in multiples. An entire period of human prehistoryis named for the earliest known alloy-- bronze.

During the Bronze Age (c. 3500-1000 b.c.) humans first fashioned tools and weapons from something other than basic materials found in nature. Humans combined copper and tin to form a strong metal that...