Variation of stacking fault energy with austenite grain size and its effect on the MS temperature of γ→ε martensitic transformation in Fe–Mn alloy

The change in MS temperature of γ→ε martensitic transformation with austenite grain size (AGS) has been investigated in relation to the stacking fault energy (SFE) in an Fe–18%Mn alloy. With increasing AGS, the MS temperature increases steeply up to 35 μm, and gradually increases in larger grains. The SFE, on the other hand, decreases abruptly until 35 μm, over which it is slightly lowered. A good linear relationship is established between MS temperature and inverse of SFE, i.e. stacking fault probability (SFP). This result suggests that the variation of MS temperature with AGS depends strongly on the change in SFE.