The influence of external stresses on the transformation behaviour in a Fe-Mn-Si alloy

The influence of external stresses on the transformation behaviour has been studied for a polycrystalline Fe-31Mn-5Si alloy exhibiting the gamma-->epsilon martensitic transformation. Samples have been loaded at temperatures above the M-s temperature, cooled with a constant external load to a temperature below the M-s temperature and subsequently heated without load to a temperature above the A(s) temperature of the alloy. Stress, strain and temperature have been continuously measured and transformation temperatures and strains have been determined from the change in strain during the transformation. It has been found that the M-s temperature during cooling with load is influenced by 0.3-2 % plastic pre-deformation of the austenite whereas there is a substantial increase in the transformation strain, i.e. variants with a favourable orientation are enhanced by pre-strain of austenite.