Alloying Metal

Metals are sometimes used in their pure form; however more often than not, they are alloyed with other metals (or carbon) to give the metal more desirable properties (depending upon role).
Transition metals form a wide range of alloys with each other.
Their atoms are of a similar size and behaviour and so the lattice structure of the metal won’t alter greatly as a result of substituting one atom for another.
Even so, alloying metals modifies the properties of the metal and usually makes it harder and less malleable.

The effect of alloying on metal properties

Metallic bonds are strong but directed between particular atoms.
When a force is applied to a metal crystal, the layers can slide past each other (slipping). After slipping has occurred, the atoms will stay in their new regular close-packed structure.
This is the reason why metals are malleable and ductile.
When an alloy is added to the metal, the orderly arrangement of the lattice is disrupted; this prevents the metal layers from sliding past each other.
Smaller atoms can also be added into the metal lattice (often non-metals such as carbon or nitrogen); these fit into the holes between the atoms.
This has the same effect of distorting the regular structure, thus making slip between the layers more difficult.