Solid solution

A solid metal in which an alloying element is dissolved, for example carbon dissolved in iron.

A solid solution behaves in a similar way to a liquid solution except that the reactions are generally much slower and are therefore carried out at higher temperatures to speed them up.

In general, as the temperature is increased, more of the alloying element can be dissolved. As the temperature is reduced, the solid solution can not hold as much alloying element and it is ejected from the solution as a precipitate. The precipitate can be the pure alloying element but is more often a compound of the alloying element and the base metal.

In iron-carbon alloys, the precipitate is cementite or iron carbide (Fe3C).