Comparisons of Modified Constitutive Models to Predict Flow Stress of Mg-13Gd-3.5Y-2Zn-0.5Zr Alloy in Hot Compression

The true stress-true strain curves of a Mg-13Gd-3.5Y-2Zn-0.5Zr alloy were acquired by isothermal compression tests at various deformation temperatures of 350–500°C and strain rates of 0.001–1 s–1. The Johnson-Cook, strain-compensated Arrhenius-type and microstructure-based models were developed and further modified to improve a prediction accuracy. The determination coefficient and 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. Meanwhile, the microstructure-based model is best suited for the prediction of high-temperature flow stress due to its very high prediction accuracy, although the calculation process is very complex. The proposed constitutive material models are of great importance in the simulation and optimization of hot working processes of Mg-13Gd-3.5Y-2Zn-0.5Zr alloys.