Martensitic Phase Transformation from Non-isothermally Deformed Austenite in High Strength Steel 22SiMn2TiB

Non-isothermal compressive deformation was performed on high strength steel 22SiMn2TiB for the study of martensitic phase transformation from deformed austenite. The transformation start temperature M _s decreased with the increase of deformation from 0 to 50 pct, and the variation of deformation rate (0.1 and 10 s⁻¹) and the appearance of deformation-induced ferrite and bainite showed no influence on the change of M _s temperature. The deformation at both the rates increased the volume fraction of retained austenite; however, the carbon content of retained austenite decreased at 10 s⁻¹ and remained basically unchanged at 0.1 s⁻¹. The yield strength of austenite at M _s temperature and the stored energy in deformed austenite were experimentally obtained, with which the relationships between the change of M _s temperature and the thermodynamic driving force for martensitic phase transformation from deformed austenite were established by the use of the Fisher-ADP–Hsu model. And finally, the transformation kinetics was analyzed by the Magee–Koistinen–Marhurger equation.