Using Optimization Method to Determine the Dynamic Recrystallization Kinetics of Q235

A coupled mathematical model based on dislocation theory is presented in the paper. It is applied to evaluation of the dynamic recrystallization kinetics using optimization method. The model does not distinguish different kinds of recrystallization, which are considered as the same process rooted in nucleation and grain growth. And the dynamic recrystallization fraction is related to the flow stress by formulations, which includes dislocation density. Flow stress is calculated by the dislocation density. The dislocation density formula takes into accounts hardening, recovery and recrystallization during the hot deformation process. In the model the variables changes are introduced by ordinary differential equations. Model parameters are defined from comparison of the calculated curves with the measured flow stress curves. That is finished through solving the nonlinear least-squares problem. Finally, in order to validate the obtained parameters, the kinetics for dynamic recrystallization obtained by the proposed model were compared with that in the literature obtained using another approach.