Temperature and strain rate dependent deformation induced martensitic transformation and flow behavior of quenching and partitioning steels

The quenching and partitioning steels have received much attention because of the material's high strength and good ductility, which results from deformation-induced martensitic transformation. To investigate the strain rate and temperature dependence of martensitic transformation and flow behavior, we conducted interrupted uniaxial tension tests and X-ray diffraction. The experiments covered a wide range of strain rate and six ambient temperatures conditions, which are in accordance with conditions encountered in sheet metal forming and car crash process. Based on the martensitic phase transformation behavior and newly proposed heat balance equation, a modified transformation kinetics law was proposed to describe both the thermal effect and positive effect of strain rate on deformation-induced martensitic transformation. The new model reproduces the martensitic phase transformation behavior of quenching and partitioning sheet steels for a wide range of strain rate and temperature conditions well.