Hot tensile deformation behavior and a fracture damage model of the wrought Mg–Gd−Y–Zn–Zr alloy

Abstract

The hot deformation behavior of the wrought Mg–Gd−Y–Zn–Zr alloy was studied by uniaxial tensile tests conducted at various temperatures (350–500 °C) and strain rates (0.1–0.0001s−1). Furthermore, the effects of the deformation parameter on the true stress−strain curves, microstructure, fracture characteristics, and fracture mechanisms were discussed, and a damage model for predicting fracture strain was established. The results are as follows. The increasing temperature or the decreasing strain rate reduce the peak stress and increase the fracture strain, except for 500 °C/0.0001s−1. The increasing in the fracture strain is attributed to the easier activation of multi−slip, the smaller size of broken 14H−LPSO during deformation, the higher fraction of fine grain generated by DRX. The β phase around the grain boundary will gradually disappear with the decrease of strain rate at high temperature (450 °C and 500 °C), which will cause DRXed−grain coarsening. Especially the alloy deformed at 500 °C/0.0001s−1, the grains are significantly coarsened. Thus, the fracture strain of the alloy deformed at 500 °C/0.0001s−1 is not greater than that of the alloy deformed at 500 °C/0.001s−1. The fracture morphology changes from the coexistence of cleavage surfaces and dimple to dimple with increasing deformation temperature and decreasing strain rate. In addition, the fracture damage predicted using the fracture damage model agreed well with the experimental results, with a maximum relative error of only 8.8%.