Relations between the lattice parameter and the stability of Austenite against epsilon martensite for the Fe-Mn based alloys

The influences of lattice parameter of austenite, the electron concentration, the yield strength of parent phase on gamma --> epsilon martensite start temperature M-S in the Fe-Mn alloys containing C, Al, Ge and Si have been experimentally investigated. The results show that the lattice parameter of austenite is more important than the electron concentration and the yield strength of parent phase in governing the gamma --> epsilon martensitic transformation in Fe-Mn based alloys. A relation between the M-S and lattice parameter of austenite in Fe-Mn based alloys is suggested. The elements Mn, C, Al, Ge, which increase the lattice parameter of austenite lower the M-S; while the element Si, which decreases the lattice parameter increases the M-S. The depressing effect of antiferromagnetic transition on the gamma --> epsilon martensitic transformation may be related to the increase of lattice parameter due to the positive magnetostriction during the antiferromagnetic transition.