Hot tensile deformation behaviors and a fracture damage model of the Mg-Gd-Y-Zn-Zr alloy

Abstract

In this study, the hot deformation of Mg-9Gd-4Y-2Zn-0.5Zr alloy was studied by the hot tensile test conducted at various temperatures (350°C–500 °C) and strain rates (0.0001–0.1s−1). Furthermore, the relationship among the peak stress, the fracture strain, fracture morphology and soften behavior was discussed, and a fracture damage model was proposed to predict the fracture failure. The results were as follows. The soften behaviors, including the twin being replaced by multi-slip and the occurrence of DRX become more obvious with the decrease of Z (Z=ε˙exp(QRT)) value, which leads to the decrease of the strain hardening exponent n determining the peak stress and the increase of the strain-rate hardening exponent m determining the fracture strain. The greater the n, the greater the peak stress; the greater the m, the greater the fracture strain. The transformation of the fracture morphology with the decreasing Z value is cleavage surfaces→ coexistence of cleavage surfaces and dimple→ dimple. The proposed fracture damage model is in good agreement with the experimental results.

Keywords

• Mg-Gd-Y-Zn-Zr alloy
• Hot tensile deformation
• Soften behavior
• Fracture damage model