Mixing Metals Together

Pure metals have limitations. Pure gold is too soft to hold its shape in jewelry. Pure iron rusts quickly and is too soft for many structural uses. Pure aluminum bends too easily for structural use.

An alloy works because the added atoms disrupt the regular arrangement of the base metal's crystal lattice. When atoms of different sizes sit in the lattice, they block the movement of dislocations — the defects that allow metal layers to slide past each other.