# Composites of Immiscible Solids - Aluminum and Lead Example

The $\ce{Al}$-$\ce{Pb}$ (aluminium-lead) phase diagram clearly depicts that when cooled from the liquid state, aluminium and lead are not miscible in the solid state, i.e. the crystal structure of only one of the components prevails while the other remains a liquid or does not interact in any way with the other in its own solidification process.

What does this have to do - if anything - with the fact that a solid combination of $\ce{Al}$ and $\ce{Pb}$ is not classified as a composite?