Material behavior and formability of magnesium AZ31 sheet alloy under warm hydroforming conditions

In this study, a hydraulic bulge test setup was developed to conduct biaxial material tests with continuous and in-line pressure and non-contact dome height measurement capabilities. Several hydraulic bulge tests were performed to investigate the material behavior of Mg AZ31B-O sheet alloy at elevated temperature levels of 100, 200, and 300°C, and at two different strain rate levels of 0.0013 and 0.013 s-1. Based on the bulge test results, flow curves as a function of strain, strain rate and temperature were then established. The flow curves were found to decrease significantly with increasing temperature and decreasing strain rate. In the second stage of this study, closed-die warm hydroforming experiments were conducted to determine the forming limits in terms of achievable smallest corner radii, highest strain, and part height without failure. The 2D and 3D profiles of the hydroformed parts were measured using stereoscopic CCD cameras. The formability (i.e., die filling, part height, and corner radii) of the magnesium sheet was found to be significantly increased with increasing temperature.