Modeling of temperature- and stress state-dependent yield and fracture behaviors for Mg-Gd-Y alloy

The research aims at characterizing and modeling the influence of temperature and stress state on the yield and fracture behaviors of an Mg-Gd-Y alloy. The mechanical experiments at 25∼300 ℃ were carried out by various designed specimens, including tension, compression and shear. The experimental result indicates that the strength of the Mg-Gd-Y alloy presents a monotonous and non-uniform downward trend as the temperature increases. The mechanical behavior at 100 ℃ and 150 ℃ are very similar, and the strength rapidly declines when the temperature is higher than 250 ℃. The tension-compression asymmetry presents the obvious nonlinear variation with the temperature and strain, which is weakened at elevated temperature. The fracture behavior belongs to the ductile fracture with tension and shear mechanisms, showing a coupling effect of temperature and stress state. A modified Zerilli-Armstrong model is proposed to characterize the plastic flow behavior with the coefficient of determination about 0.99, which is prior to the Johnson-Cook and Zerilli-Armstrong models. The Cazacu-Barlat2004 yield function is established to describe the temperature- and strain-related non-uniform evolution characteristic, and capture the fracture-related variables of all fracture tests with the acceptable prediction accuracy. The temperature-dependent parameter is introduced into the DF2016 fracture criterion to predict the onset of fracture under various temperatures and stress states with a small prediction error. The numerical simulation is conducted to validate the reliability and practicability of the established model.