There are two types of alloys:
Element with similar chemical properties and size. Atoms of another element kind of “replaces” some of the cations in the metallic lattice.
Atoms with a large difference in size. The smaller atom is kind of squished in to the metallic lattice. This is the type of lattice that carbon and iron forms.
Carbon and Iron alloys:
Components: Iron, carbon (0.5%)
Properties: Strong, easily worked and welded
Uses: Girders, car bodies
Components: Iron carbon (1%)
Properties: Strong, hard, brittle
Uses: Tools, knives, cast iron
Kind of hard to explain without diagrams if you still don’t get it try searching for: