Microstructure and mechanical properties of AZ80 magnesium alloy tube fabricated by hot flow forming

Flow forming is a plastic deformation process to produce thin-walled and high-precision cylindrical components. In this study, the hot flow forming of Mg-8.5Al-0.5Zn-0.2Mn (AZ80) alloy tubes was conducted innovatively. The effects of processing parameters including flow forming temperature, spindle speed, feed ratio and thickness reduction on the microstructures and mechanical properties of AZ80 alloy tubes were investigated. The results show that a more unanimous and raised grain size appeared with deforming temperature from 300 to 420 °C. The variation of spindle speed and feed ratio had a slight influence on the microstructure, but an obvious influence on the tensile properties, particularly the elongation. With increasing the thickness reduction, the grain size decreased while the micro-hardness increased significantly. The electron backscatter diffraction (EBSD) results show that the c-axes of most grains are approximately parallel to the radial direction. And likewise, they have a slight deflection towards the axial direction. Furthermore, ultimate tensile strength (UTS) of 308 MPa and elongation of 9.8% were obtained when the hot flow forming was carried out under a temperature of 420 °C, a spindle speed of 400 rev/min, a feed ratio of 0.1 mm/rev and a thickness reduction of 45%.