Iron-carbon alloy phase diagram: In a sense, iron-carbon alloy phase diagram is a tool for studying iron-carbon alloy, a theoretical basis for studying the relationship between composition, temperature, microstructure and properties of carbon steel and cast iron, and a basis for formulating various hot working processes.

The phase diagram of iron-carbon alloy is actually the phase diagram of iron and iron carbide. The basic components of iron-carbon alloy should also be pure iron and iron carbide. Iron has isomorphic transformation, that is, it has different structures in solid state. Iron and carbon with different structures can form different solid solutions, and the solid solution on the phase diagram of iron and iron carbide is interstitial solid solution. Because of the different pore characteristics in the crystal lattice, their carbon solubility is also different.