Effects of temperature and strain rate on deformation behaviors of an extruded Mg-5Zn-2.5Y-1Ce-0.5Mn alloy

Abstract

An extruded Mg-5Zn-2.5Y-1Ce-0.5Mn alloy with uniform fine α-Mg grains, dispersed W-phase and T-phase and weak basal texture was prepared by the semi-continuous casting and one-pass extrusion methods. The deformation behaviors of the extruded alloy were tested at a temperature range from room temperature (RT) to 350 °C and a strain rate range from 1×10−2s−1 to 4×10−4s−1. The results and relevant mechanisms were analyzed by using the measured data of the strain rate sensitivity (m) and the activation energy (Q) and the observations of the morphologies of deformation and fracture surfaces. It was demonstrated that the tensile strengths decrease, while the elongation to failure tends to increase with increasing temperature or decreasing strain rate. The variation in mechanical properties with increasing temperature mainly arises from a change in opening deformation mechanisms from the dislocation slip at RT to the dislocation climb at 250 °C to the grain boundary (GB) sliding at 350 °C. At RT, the slightly decreased tensile strengths and slightly increased elongation to failure with decreasing strain rate are mainly attributed to the weak sensitivity of the dislocation slip to strain rate. At 250 °C, the lower tensile strengths and the larger elongation to failure at 4×10−4s−1 than that at 1×10−2s−1 are mainly attributed to the occurrence of the dynamic recrystallization (DRX) at lower strain rate, while such DRX does not occur at higher strain rate. At 350 °C, the lower tensile strengths and the much larger elongation to failure at 4×10−4s−1 than that at 1×10−2s−1 are attributed to the GB sliding accommodated by the lattice diffusion at lower strain rate, while the GB sliding at higher strain rate is accommodated by the GB diffusion.