Metal alloys are usually formed by mixing two or more metals in their liquid state. The two most common doping methods are the mechanisms substitutions and introducing.
The substitution mechanism involves the simple transfer of atoms from one lattice to another lattice. An example of substitutional alloying is copper-nickel alloys, in which there is an exchange of atoms between the lattices of copper and nickel.
Alloying by introduction
For implantation doping, a large difference in the sizes of the participating atoms is required. The dimensions of the carbon atom in thirty times less the size of the iron atom. Therefore, for iron-carbon alloys, the mechanism of alloying by insertion can proceed quite easily. Under certain conditions, small iron atoms enter into the atomic lattice of iron - in the spaces between the atoms (picture). This simplifies the principle of alloying carbon steels.