Achieving Superplasticity in AZ31 Magnesium Alloy Processed by Hot Extrusion and Rolling

Abstract

Experiments were conducted on ultrafine-grained AZ31 magnesium alloy sheet which was prepared through nano-grained powders processed by hot extrusion at 300 °C plus hot-rolling for four passes at 200. The superplastic behavior had been evaluated in a low-temperature range of 423-523 K and strain rates varied from 5 × 10−4 to 5 × 10−3 s−1. The experiment results showed that tensile testing revealed the superplastic elongations with a maximum measured elongation of 227% when tested at 523 K and strain rate of 5 × 10−4 s−1. The superplastic deformation behavior was attributed to the ultrafine-grained microstructures. The measured elongations mainly depended upon the initial strain rate and temperature, and the strain rate sensitivity m was ~0.5 for this condition. The results indicated that powder metallurgy and subsequent hot extrusion plus rolling were promising approaches to produce the ultrafine-grained magnesium alloy sheet with superplasticity.