Phase Diagrams of the Iron - Carbon System

Below, the phase diagram of Fe - Fe₃C, as we already know it, is contrasted with the phase diagram of Fe- C

Only the latter is a "true" phase diagram showing stable equilibrium phases. The former, however, is simply more important in a practical sense because it governs what we usually call "plain carbon steels".

Phase diagram iron - cementite	Phase diagram iron - carbon

As stated in the text, the difference is rather small.

Mit Frame

8.4.1 Plain Carbon Steels