Experimental investigations on the material behavior and formability of magnesium AZ31 sheet under warm hydroforming conditions

Use of magnesium alloys for automotives components is wildly accepted as one of the major keys for improving fuel economy. However, with the poor formability of these alloys at ambient temperature, fabrication processes at elevated temperatures of magnesium alloys are required. In this study, the material behavior and forming limits of MgAZ31 sheets are investigated at elevated temperatures and hydroforming loading conditions. Specifically, hydraulic bulge tests were carried out at elevated temperatures (room-300°C) and strain rates (0.0013 and 0.013s^-1) to determine the material flow stress curves and the maximum elongation. The bulge test results showed a significant decrease in flow stress and a large increase in maximum elongation with increasing temperature and/or decreasing strain rate. In addition to the bulge tests, a set of closed-die hydroforming experiments were conducted at similar temperature range in order to determine the formability of the sheets (e.g., die filling, thinning, and corner filling). The closed-die experimental results had confirmed the significant increase in sheet formability with increasing temperature.