Phase Diagrams

· At (723 - ε) C, the 50% γFe with the eutectoid composition transforms to pearlite with 88 % αFe and 12 % Fe₃C.
· The 50 % αFe on the Austenite grain boundaries is thermodynamically stable both above and below 723 C and does not change during the eutectoid decomposition so that: Total wt % αFe = 50% + (50% x 88%) = 94% in the final equilibrium state.

· The room temperature microstructure of the equilibrium hypo-eutectoid alloy is shown. The pro-eutectoid ferrite is white.
· Ferrite is solid-solution hardened by interstitial carbon and is ductile. The hypo-eutectoid alloy is, therefore, a relatively ductile steel.

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