The Influence of Deformation Mechanisms on Rupture of AZ31B Magnesium Alloy Sheet at Elevated Temperatures

Gas-pressure bulge tests were conducted on Mg alloy AZ31B wrought sheet until rupture at temperatures from 250 to 450°C. The rupture orientation was observed to change with forming pressure, which controls the forming strain rate, at 350 to 450°C. This phenomenon is a result of associated changes in the mechanisms of plastic deformation. At slow strain rates (≤ 3 × 10−2 s−1), cavity interlinkage associated with grain boundary sliding (GBS) creep induced rupture along the sheet rolling direction (RD). At fast strain rates (≥ 3 × 10−2 s−1), flow localization (necking) associated with dislocation-climb-controlled (DC) creep induced rupture along the long-transverse direction (LTD), a result of mild planar anisotropy. Biaxial bulge specimens tested at 250 to 300°C ruptured explosively, hence preventing any further analysis.