Austenite Stability and Its Effect on the Ductility of the Cold-rolled Medium-Mn Steel

The mechanical and thermal stability of retained austenite in the cold-rolled medium-Mn (Fe-0.1C-5Mn) steel were studied by the tensile deformation at different temperature. The volume fractions of retianed austenite and microstructure of the starting and deformed materials were analyzed by X-ray diffraction, the scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD). It was found that the volume fraction of retained austenite gradually decreased with strain increasing during tensile deformation. It showed high mechanical stability of retained austenite, which resulted in good comprehensive mechanical properties with ultrahigh strength and plasticity. Meanwhile, the tensile results at different temperature showed pretty high plasticity at low temperature (-40 degrees C and -80 degrees C) tensile deformation of the cold-rolled steel, which indicated the retained austenite maintained, certain stability at low temperature. The results of this study indicate that the ductility in the medium-Mn steel with high contents of retained austenite can be altered by control of the austenite stability.