Microstructure and mechanical properties of AZ31 magnesium alloy prepared using wire arc additive manufacturing

AZ31 magnesium alloy structural parts were formed using the wire arc additive manufacturing technology (WAAM), and the microstructure and mechanical properties of the additive–substrate interface bonding zone and the additive zone were studied. Due to the repeated heating under the heat source during the additive manufacturing process, the longitudinal section of the additive zone had obvious non-uniform features. The grain size of the longitudinal section of the additive zone increased from 4.27 µm to 9.51 µm from the bottom zone to the top zone. The average fraction of "hard" grains in cross section was higher than that in longitudinal section, indicating that the cross section showed less plastic strain accumulation, resulting in lower plastic than the longitudinal section. The mechanical property anisotropy of the cross section was stronger because of its higher fiber texture strength. At the same time, the longitudinal section microhardness of the additive zone increased from 74.22 HV to 81.46 HV from the top zone to the bottom zone. The tensile strength of the WAAM AZ31 magnesium alloy in the vertical direction was 286.47 MPa, and its elongation rate was 15.89 %, which was considerably greater than the ultimate tensile strength of the cast and the extruded AZ31 magnesium alloy.