What is the structure of interstitial alloys and how does it differ from substitutional alloys?

Interstitial alloys have small atoms occupying the spaces between the larger atoms in the crystal lattice.

In interstitial alloys, small atoms such as carbon, nitrogen, and hydrogen occupy the interstitial sites between the larger atoms in the crystal lattice. These small atoms do not replace the larger atoms, but rather fit into the gaps between them. This results in a distortion of the crystal lattice, making the alloy harder and stronger than the pure metal. Examples of interstitial alloys include steel, which is made by adding carbon to iron.

In contrast, substitutional alloys have atoms of a different element replacing some of the atoms of the original metal in the crystal lattice. This results in a change in the properties of the alloy, such as its melting point, density, and electrical conductivity. Examples of substitutional alloys include brass, which is made by adding zinc to copper.

Overall, the structure of interstitial alloys differs from substitutional alloys in that small atoms occupy the interstitial sites between the larger atoms in the crystal lattice, rather than replacing them. This results in a distortion of the crystal lattice and an increase in the strength and hardness of the alloy.