Iron–Carbon Phase Diagram

A geometric figure, in which temperature is indicated by the y-coordinate and carbon content by the x-coordinate, that indicates the phases of the binary alloy with constituent elements iron and carbon and the equilibrium relation between these phases under near-equilibrium conditions (iron–graphite) and metastable conditions (iron–iron carbide) in various temperatures. It is also known as iron–carbon equilibrium diagram or iron–carbon state diagram.

Brief History

Advent of iron–carbon phase diagram was closely related to the concept of phase transition critical point of steel. In 1868, the Russian metallurgist D. K. Chernoff, by drawing on a great deal of practical work in forging, quenching, tempering, and fracture inspection of gun barrel, concluded that steel must be heated to above the temperature “a” so that it can be hardened after quenching, and quenching under this temperature will make the steel soft instead of hard. Therefore, he explicitly proposed the concept of “critical...