Study on Flow Stress Model and Processing Map of Homogenized Mg-Gd-Y-Zn-Zr Alloy During Thermomechanical Processes

Quantities of billets were compressed with 50% height reduction on a hot process simulator to study the plastic flow behaviors of homogenized as-cast Mg-13Gd-4Y-2Zn-0.6Zr alloy. The test alloy was heat treated at 520 °C for 12 h before thermomechanical experiments. The temperature of the processes ranged from 300 to 480 °C. The strain rate was varied between 0.001 and 0.5 s⁻¹. According to the Arrhenius type equation, a flow stress model was established. In this model, flow stress was regarded as the function of the stress peak, strain peak, and the strain. A softening factor was used to characterize the dynamic softening phenomenon that occurred in the deformation process. Meanwhile, the processing maps based on the dynamic material modeling were constructed. The optimum temperature and strain rate for hot working of the test alloy were 480 °C and 0.01 s⁻¹, respectively. Furthermore, the flow instability occurred in the two areas where the temperature ranged from 350 to 480 °C at strain rate of 0.01-0.1 s⁻¹, and the temperature ranged from 450 to 480 °C with a strain rate of 0.1 s⁻¹. According to the determined hot deformation parameters, four components were successfully formed, and the ultimate tensile strength, yield strength, and elongation of the component were 386 MPa, 331 MPa, and 6.3%, respectively.