Formability of AZ31 magnesium alloy sheets during magnetic pulse bulging

Electromagnetic forming (EMF), i.e., magnetic pulse forming, with and without an Al driver sheet is experimentally performed to investigate the formability of an AZ31 magnesium alloy sheet during high speed forming. The formability of the magnesium alloy AZ31 during EMF is compared with that during traditional quasi-static tests. The results show that the formability of the magnesium alloy sheet undergoing the EMF process without the driver sheet is increased compared with that during quasi-static tests. To improve the energy efficiency of and to accelerate the AZ31 sheet, an Al driver sheet was used. The energy efficiency increases from 0.2% (no driver) to 1.8% (with a 2 mm driver sheet). The forming limits of the magnesium alloy samples with the 2 mm driver sheet are dramatically higher than those during quasi-static tests. The major and minor principal strains with the 2 mm Al driver sheet increase by approximately 148% and 184%. The forming limits with 0.5 and 1 mm driver sheets are similar to those during the EMF process without the driver sheet, enabling the AZ31 sheet to be formed at a higher strain. Increases in the major and minor principal strains with the 0.5 mm driver sheet of approximately 68% and 72%, respectively, are achieved. According to the analysis of the crack fracture observations of the samples with the driver sheets, the fracture surfaces have obvious plastic dimples, which exhibit typical ductile rupture. The test results indicate that the formability could be significantly improved. The EMF process could be used in the manufacturing of AZ31 magnesium alloy sheet parts at room temperature.