Formability of AZ31B magnesium alloy extruded tube under internal high pressure

Tension test and hydrobulging test at different temperatures were used to investigate the formability of AZ31B magnesium alloy tube manufactured by bridge die extrusion. The results show that the tension formability along the extrusion direction increases significantly with the increase of temperature, while the maximum hydrobulging ratio does not change accordingly. The difference of properties in axial direction and hoop direction induced by extrusion process is one of the main reasons for the anisotropy character of the tube. In addition, for the tube manufactured by bridge die extrusion, there exists several weld lines along the extrusion direction, which will become the weakest positions at elevated temperature where fracture will first occur, consequently resulting in the decrease of the tube formability during hydrobulging.