Development of constitutive material models to predict high-temperature flow stress in a Mg-13Gd-3.5Y-2Zn-0.5Zr alloy

The true stress–true strain curves of a Mg-13Gd-3.5Y-2Zn-0.5Zr alloy were obtained by isothermal uniaxial compression test using a thermo-mechanical simulator at various deformation temperatures of 350–500°C and strain rates of 0.001–1 s^–1. Three constitutive material equations, the modified Johnson-Cook model, the strain-compensated Arrhenius-type model, and the microstructure-based constitutive model, were developed and compared on the experimental data. The modified Johnson-Cook model and the microstructure-based constitutive model were further modified to improve the prediction accuracy. The determination coefficient and the average absolute relative error were 0.9380, 10.67% for the modified Johnson-Cook model, 0.9536, 6.38% for the strain-compensated Arrhenius-type model, and 0.9813, 3.37% for the microstructure-based model, respectively. As a result, the modified Johnson-Cook model and the Arrhenius-type model could not correctly predict the high-temperature flow stress of this alloy. The microstructure-based constitutive model is best suited for the prediction of high-temperature flow stress, although the calculation process is very complex. The proposed constitutive material equations are of great importance in the simulation and design of hot working processes of Mg-13Gd-3.5Y-2Zn-0.5Zr alloys.