A model was proposed for the evaluation of the stacking fault energy in Fe–Mn–C austenitic alloys at various temperatures. It accounted for the variation of the Gibbs energy of each element during the austenite to ε-martensite transformation, plus their interaction. The Gibbs energy due to the antiferromagnetic to paramagnetic transition was also taken into account. The results revealed a decrease in the stacking fault energy with temperature, with saturation below the austenite Néel temperature. The results agreed with mechanical and thermal martensitic transformation limits proposed by Schumann. The plasticity mechanisms depended upon the stacking fault energy. The mechanical martensitic transformation occurred below 18mJ/m2, and twinning between 12 and 35mJ/m2; in agreement with tensile tests and with the deformation microstructures observed in an Fe–22Mn–0.6wt%C alloy at 77, 293 and 693K.

Correlations between the Calculated Stacking Fault Energy and the Plasticity Mechanisms in Fe–Mn–C Alloys. S.Allain, J.P.Chateau, O.Bouaziz, S.Migot, N.Guelton: Materials Science and Engineering A, 2004, 387-389, 158-62