The interstitial alloy between carbon and iron has a complex phase diagram. A compound, Fe 3 C with the fixed composition Fe-6.7 wt % C bounds one end of this diagram and pure iron the other end. Pure ...

and the compound Fe3C with the composition Fe - 6.7 wt % C. Austenite is a solid and, in general, will be polycrystalline. The formation of ferrite and iron carbide will start at the austenite grain ...