THE INFLUENCE OF EXTERNAL STRESSES ON THE TRANSFORMATION BEHAVIOR 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 g amma-->epsilon martensitic transformation. Samples have been loaded at temperatures above the M-s temperature, cooled with a constant extern al load to a temperature below the M-s temperature and subsequently he ated without load to a temperature above the A(s) temperature of the a lloy. Stress, strain and temperature have been continuously measured a nd transformation temperatures and strains have been determined from t he 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 substantia l increase in the transformation strain, i.e. variants with a favourab le orientation are enhanced by pre-strain of austenite.