Formability testing of AZ31B magnesium alloy tube at elevated temperature

Magnesium alloy is a promising material for reaching the goal of weight reduction in automotive and aerospace industry. The mechanical properties of AZ31B seamless tube were tested by ring hoop tension test and compared with the results by axial tension test. Hydro-bulge test and newly proposed flatten-hydro-bulge test were also carried out to evaluate the formability of the tube. The effect of forming temperature and flattening displacement on the maximum expansion ratio and bursting pressure were measured and discussed. A tubular part with curved axis and different cross-sections was then manufactured successfully. It was found that the changing tendency of total elongation in hoop direction is quite different with that along axial direction. As temperature increased from RT. to 300 °C, two peaks of total elongation in hoop direction occurred at about 150 °C and 300 °C. In hydro-bulge test, the maximum expansion ratio increased as temperature increasing and reached the maximum value about 30% at 170 °C, then decreased quickly at higher temperature until 230 °C. In flatten-hydro-bulge test, flattening deformation has significant effect on the subsequent hydro-bulging process, and both maximum expansion ratio and bursting pressure decreased as flattening displacement increased. This should be taken into account during part design and process determining.