High Strain Rate Superplasticity and Microstructure Study of a Magnesium Alloy

Abstract

Superplastic-like behavior was found in a commercial large-grained Mg-3Al-1Zn alloys (AZ31), at high temperature and high strain rate regime. The creep behavior of this material was studied from RT to 550°C and the strain rates of 0.001 s -1 ∼1 s -1 , and the maximum elongation to failure of 170% was obtained at 0.01 s -1 and at 500°C (or 0.84 T m ), which is much higher than the equivalent temperature of most known superplastic materials. Optical microscopy, transmission electron microscopy (TEM) and scanning electron microscopy with electron backscattering diffraction technique (SEM-EBSD) were used to investigate the microstructure and deformation mechanisms involved. It is evident that high temperature and high rate dislocation creep played a critical role at the early stage deformation in breaking down the initial large grains without fracture, and combined GBS and dislocation creep define the steady-state grain size and control the quasi-superplastic behavior.