The eutectoid phase transition in the iron carbon system takes place at 727 C. The three components in equilibrium at this temperature are Austenite, g, with the composition Fe - 0.77 wt % C, Ferrite, ...

The diagram illustrates the transition zone (yellow) and also shows two constant cooling rate trajectories (they are curved because the time scale is logarithmic). If the ... Martensite does not start ...