Superplastic Instability and Damage Evolution of AZ31B Magnesium Alloy Shee

Abstract

Superplastic instability and damage evolution of AZ31B magnesium alloy sheet were investigated in this paper. Maximum elongation of 216% and strain rate sensitivity of 0.36 were obtained at 723k and a strain rate of 1×10-3s-1, whose fracture was due to the growth and interlinkage of cavities that nucleated at grain boundary. After superplastic tensile tests and quantitative analysis of cavity volume fraction, A cavity growth model were established, and the damage evolution equation based on the law of the micro-damage evolution and statistical mechanics was derived out, and damage characteristic parameters as well as the critical value of damage variable were identified so as to provide a theoretical ground on which the plastic forming technology of magnesium alloy sheet can be optimized.