Magnetic investigation of the effect of α′-martensite on the properties of austenitic stainless steel

In this paper some phase transformations of the AISI 304 austenitic stainless steel are studied. The appearance of the strain induced α′-martensite phase due to cold rolling and elongation was investigated by different magnetic measurement techniques. It was demonstrated that the type of deformation and the rate of deformation strongly influence the amount of α′-martensite phase. It is supposed that the additional stress due to the specific volume change of γ→α′ transformation can improve the plastic deformation of the neighbouring austenite grains in the highly deformed range which has increasing effect on the amount of α′-martensite phase. The reverse transformation of the α′-phase back to γ-phase due to heat treatment is also studied. It was proved that the magnetic and hardness recovery processes started at different temperatures. The paper demonstrates the application possibility of magnetic measurements in case of the investigated metallurgical problem.