To make an alloy, manufacturers melt the primary metal first. Next, they dissolve the other elements into the liquid metal. As the mixture cools, it forms a solid crystal lattice.
There are two main types of alloys. Substitutional alloys form when the added atoms replace some of the primary metal atoms in the lattice. This replacement requires the different atoms to be roughly the same size.
Interstitial alloys form when very small atoms fit into the tiny spaces between the larger metal atoms. Carbon and nitrogen often fill these small gaps. Mixing different atom sizes disrupts the neat, repeating rows of the metal crystal.
This disruption prevents the atomic layers from sliding past each other easily. This resistance to sliding makes the alloy much harder and stronger than the pure metal. A common student misconception is that alloys are chemical compounds.
In reality, alloys are physical mixtures, so their proportions can be adjusted to change their properties. Alloys can also improve resistance to rust and change how heat or electricity flows through the material.