Superplastic Process and Deformation Mechanism of Asymmetrically Rolled AZ31 Magnesium Alloy

AZ31 magnesium alloy sheet was prepared by asynchronous rolling process.From 300℃ to 450℃,tensile test was conducted with different strain rates of 5×10-3,1×10-3s-1 and 5×10-4s-1respectively to investigate the superplastic deformation behavior of AZ31 magnesium alloy.The value of the strain rate sensitive index m,the superplastic deformation activation energy Qand the threshold stress σ0 were also calculated.The superplastic deformation mechanism of AZ31 was investigated through observation of the fracture morphology of the tensile specimens by EBSD and SEM.The results show that the plastic deformation capacity of AZ31 magnesium alloy enhances with increasing deformation temperature and decreasing strain rate.AZ31 magnesium alloy exhibits good superplasticity,and maximum elongation-to-failure of 206% at 400℃ when the strain rate is 5×10-4s-1,and the m value is 0.72.Furthermore,the superplastic deformation of the asynchronous rolled AZ31 magnesium alloy at 400℃relies on the joint effects of grain boundary sliding(GBS)controlled by lattice diffusion and basal slip.