Martensitic transformation in Fe-Mn-Si based alloys

The stacking fault energy (SFE) or the stacking fault probability plays an important role in the determination of the critical driving force Delta G(gamma-->epsilon) for the martensitic transformation fcc(gamma)-->hcp(epsilon) in ternary Fe-Mn-Si alloys, Delta G(gamma-->epsilon) increases with the content of Mn and decreases with that of Si. Thermodynamical prediction of M-s in ternary Fe-Mn-Si alloys is established. The fcc(gamma) --> hcp(epsilon) martensitic transformation in Fe-Mn-Si is semi-thermoelastic and the nucleation process does not strongly depend on soft modes. Nucleation of epsilon-martensite is not dominated by a pole mechanism. Based on the phenomenological theory of martensite crystallography, a shuffle on (0001)(hep) planes is required when d(111) not equal d(0002). The derived principal strains for the Bain distortion are smaller. i.e. more reasonable than the values given by Christian. Alloying elements which strengthen the austenite, lower the SFE of the gamma phase and reduce the T-N(gamma) temperature may be beneficial to the shape memory effect (SME) of Fe-Mn-Si based alloys. (C) 1999 Elsevier Science S.A. All rights reserved.