Gas-Pressure Bulge Forming of Mg AZ31 Sheet at 450°C

Magnesium (Mg) sheet materials, such as wrought AZ31, possess low densities and high strength- and stiffness-to-weight ratios. These properties suggest that the use of Mg sheet is viable for reducing vehicle weight, an important goal of the automotive industry. Magnesium exhibits poor ductility at room temperature, but high-temperature forming processes may be used to manufacture complex vehicle closure panels. Tensile tests are the most common method of characterizing the plastic deformation of sheet materials. However, gas-pressure bulge tests may be more representative of the stress states that occur during the manufacture of sheet metal components. This study investigates the plastic deformation of AZ31 sheet during both biaxial and plane-strain gas-pressure bulge forming at 450°C. The heights and thicknesses of formed specimens are measured and compared. The deformation behaviors of the AZ31 sheet are related to observations of grain growth and cavitation that occur during forming.