Modeling of Flow Stress Considering Dynamic Recrystallization for Magnesium Alloy ZK60

Hot compressive deformation behavior of ZK60 magnesium alloy was investigated at the temperature range from 523 to 673K and strain rate range from 0.001 to 1s-1 on Gleeble-1500 thermal simulator. The results show that flow stress of ZK60 magnesium alloy decreases with the increase of deformation temperature and the decrease of strain rate. The flow stress curves obtained from experiments are composed of four different stages, i.e., work hardening stage, transition stage, softening stage, and steady stage, while for the relative high temperature and low strain rate, transition and softening stages are not very obvious. The onset of dynamic recrystallization (DRX) occurred before the stress peak in true stress-true strain curve. The critical stress characterizing the onset of DRX rises with the increase of strain rate and the decrease of deformation temperature. A method to predict flow stress considering the effect of true strain was presented. Flow stress model is expressed by nine independent parameters, and they are obtained by the least-square method. The predicted stress-strain curves are in good agreement with the experimental results, which confirmed that the proposed model can give an accurate and precise estimate of the flow stress for ZK60 magnesium alloy.