Formability curves of AZ31 alloy sheet at high temperatures

Nowadays, the AZ31 magnesium alloy sheet has received great attention due to its mechanical properties, notably its low density and high specific strength, and its potential for thin-walled components and sheet parts in the automotive industry. The present work examines the influence of forming process temperature on the formability curves of AZ31 magnesium alloy sheet, using the strain gradient evolution model that predicts the onset of local necking, i.e., the forming limit curve (FLC) from material plastic properties and initial thickness imperfections. The effect of plasticity parameters such as work-hardening coefficient, strain rate sensitivity coefficient and normal anisotropy for various temperatures are investigated in AZ31 alloy sheet formability curve. The theoretical analyses for forming limit curve predictions at high temperatures are compared with the experimental results available in the literature for various temperatures ranging from 100°C up to 300°C. The correlation is reasonably good. The forming limit curve depends greatly upon the strain rate sensitivity, M-value, and the work hardening coefficient, n-value. Other relevant aspects of the mechanics of sheet metal forming modeling are also discussed.