Microstructure evolution and unified constitutive equations for the elevated temperature deformation of SAE 52100 bearing steel

Microstructure evolution and hot deformation behaviors of bearing steel SAE 52100 were investigated by hot compression test at temperatures from 950°C to 1160 °C and strain rates from 0.1s−1 to 10.0s−1. The effects of process parameters (strains, strain rates and temperatures) on recrystallization behavior and plastic flow behavior were discussed. A set of unified visco-plastic constitutive model was built using internal state variables modeling method to predict microstructure evolution and flow stress of bearing steel SAE 52100 during hot deformation. Material parameters within constitutive model were determined using genetic algorithm (GA) optimization technology. The developed model was validated using experimental average grain size, recrystallized fraction and effective stress. Good agreements have been obtained for the predicted and experimental results. It indicates that the derived constitutive model is reliable. Microstructure evolution of SAE 52100 steel in hot metal forming was analyzed using the derived model.