High Temperature Creep and Superplasticity in a Mg-Zn-Zr Alloy

Creep and superplasticity were investigated by testing a fine-grained extruded Mg-Zn-Zr magnesium alloy under a wide range of applied stress in the temperature range between 100 and 300 °C. Grain boundary sliding became the dominating mechanism at 200 °C, leading to a true superplastic behaviour at 300 °C, where superplasticity was attained even under relatively high strain rates (5×10 -3 s -1). By contrast, for lower temperatures, the straining process was controlled by dislocation climb. A comprehensive model, taking into account the simultaneous operation of the different mechanisms, was developed to describe the strain rate dependence on applied stress. © 2012 The Chinese Society for Metals.