Optimizing Process Parameters of As-Homogenized Mg-Gd-Y-Zn-Zr Alloy in Isothermal Uniaxial Compression on the Basis of Processing Maps via Prasad Criterion and Murty Criterion

Isothermal compression experiments of as-homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy are conducted at temperature range of 673-773 K (400-500 °C) and strain rate range of 0.001-1 s⁻¹ in order to identify the optimized processing parameters. Results show that flow stress decreases with the decreasing strain rate at a given temperature and increases with the decreasing temperature at a specific strain rate. Based on the obtained true stress-strain curves, processing maps based on the Prasad criterion and the Murty criterion are separately constructed. Obviously, distributions of power dissipation and the instability regime in the case of the Prasad criterion are different from the corresponding ones in the case of the Murty criterion during hot deformation. Microstructure observations on deformed samples confirm that kink band and dynamic recrystallization, rather than microcrack and flow localization, occur at 698 K and 0.01 s⁻¹. This issue verifies the accuracy of instability regions determined on the base of the Murty criterion. Consequently, the processing window determined on the base of the Murty criterion is more reliable than that identified on the base of the Prasad criterion. The optimized processing parameters are finally ascertained to be 698-748 K, 0.001-0.01 s⁻¹, and 748-773 K, 0.01-0.1 s⁻¹.