Study on DC Double Pulse Metal Inert Gas (MIG) Welding of Magnesium Alloy

This article gives a preliminary research on direct current (DC) double pulse metal inert gas (MIG) welding of magnesium alloys. It will be an effort for broadening the application of this new MIG welding process. The unique parameters of DC double pulse MIG welding are selected to investigate their effects on weld bead geometry size and appearance of AZ31B Mg alloy, and the principles of their effects are summarized. Then, butt joints are produced with optimum and stationary parameters by using the new process, and high quality surfaces without spattering, undercut, or discontinuous beads are obtained. For verifying the reliability of this new process on welding of Mg alloy, microstructure, mechanical property, and fracture characteristics of the butt joint are analyzed in detail. Results show the joint has fine homogenous microstructure and high ultimate tensile strength, which is up to 96% of that of the base metal. The fracture surfaces of the butt joints and base metal show a mixed fracture characteristic with tearing cleavage planes and deformed dimples.