Joint characteristics of magnesium/steel dissimilar metals during bypass-current MIG welding-brazing

Bypass-current MIG welding-brazing of AZ31 magnesium alloy and Q235 galvanized steel was carried out. The results show that the technology could obtain stable welding process and good bead appearance. The optical microscopy, high-speed cameras and tensile testing machine were applied to observe and analyze the joint morphology, droplet transfer process and mechanical properties. It was found that the repelled transfer of droplet in the welding process prolonged the droplet transfer time,resulting in more uniformly wetting and spreading of droplet and integration of alloying elements in the interface. The tensile strength reached 133 MPa,about 70% of the base material. The joint fracture occurred in the magnesium weld, displaying ductile fracture features.