Hot deformation behaviors and processing maps of Mg-Zn-Er alloys based on Gleeble-1500 hot compression simulation

The hot deformation behaviors of as-solution Mg-xZn-yEr alloys (x/y=6, x=3.0, 4.5 and 6.0; y=0.50, 0.75 and 1.00) were investigated on Gleeble-1500 thermal simulator in a temperature range of 200-450 °C at a strain rate of 0.001-1 s−1. The true stress-strain curves showed the dynamic competition between the working hardening and working softening mainly due to the dynamic recrystallization (DRX) occurring during hot compression. The constitutive equations were constructed which could accurately predict the peak stress of the alloys. The addition of Zn and/or Er resulted in higher deformation activation energy for Mg-3Zn-0.5Er (alloy A). The processing maps were constructed as function of the temperature and the strain rate, providing the optimum hot working conditions (i.e., at strain of 0.3, Mg-3Zn-0.5Er (alloy A): 380-430 °C, <0.1 s−1; Mg-4.5Zn-0.75Er (alloy B): 380-450 °C, 0.01-0.1 s−1; Mg-6Zn-1Er (alloy C): 390-440 °C, 0.01-0.1 s−1). The as-solution treated Mg-4.5Zn-0.75Er (alloy B) demonstrated more optimum hot working window comparing with Mg-3Zn-0.5Er (alloy A) and Mg-6Zn-1Er (alloy C).