Phase Diagrams

· Important thermodynamic equilibrium micro-structures are produced by the all solid state eutectoid phase transformation from austenite to ferrite and iron carbide at the 727 C eutectoid invariant temperature:
γ -> α + Fe₃ C
· The transition is illustrated for the eutectoid alloy: Fe- 0.77 wt % C
· The lever rule can be applied to this 1080 steel just below the eutectoid temperature to give the ferrite (α-Fe) and cementite (Fe₃C) weight percents at 727 C.

From: Callister, "Materials Science and Engineering," Wiley (1994)