Papers by Keyword: MIG Arc Welding

Abstract: The microstructure and cracking characteristics of MIG welded magnesium alloy (AZ91D) joint, and the effect of welding speed on cracking susceptibility have been investigated. The result indicates the welded joint consists of primary α-Mg and divorced phases (eutectic α-Mg + eutectic β-Mg₁₇Al₁₂), the latter mainly distributing along the α-Mg grain boundaries. The weld of the magnesium alloy displays a high cracking susceptibility. The cracks are mainly formed in the arc crater at the end of the weld. These cracks propagate along the α-Mg grain boundary, and they belong to the solidification cracking. These solidification cracks are resulted by the joint function of the low melting point liquid film in the weld and the tensile stress suffered by the weld metal during the solidification process. The low melting point liquid film is the internal cause to form the solidification cracks, while the tensile stress is a necessary condition. Limiting the amount of the low melting point eutectic and decreasing the tensile stress of the welding joint are two effective methods to improve the solidification cracking susceptibility of the magnesium alloy weld.

Abstract: Through the metal inert gas welding (MIG) experiment, the effects of the different welding parameters on the microstructure, the weld configuration and the mechanical properties of the joint of the magnesium (Mg) alloy AZ31B were analyzed. The results indicate that with the increase in the welding current, the microstructure change of the weld is characterized by the grain coarsening, and the microstructure change of the heat affected zone is characterized by the grain coarsening and the broadening of the heat affected zone. An exorbitant welding current is inimical to the weld configuration. With the increase in the welding speed, the welding linear energy decreases, inducing the formation of the finer equiaxed grains in the weld. Moreover, the grains in the heat affected zone are also with the trend of the refinement, and thus the mechanical properties of the joint increase. The optimal welding current and speed in our experiment are 160-170A and 400-450mm/min, respectively.