Microstructure characteristics in TIG welded joint of Mg/Al dissimilar materials

The microstructure performance of Mg/Al TIG welded joint was studied by means of metallography, micro-hardness test and SEM. The test results indicate that the structure close to weld metal is columnar crystals, which grow into the weld metal. The weld metal was mainly composed of dendrite crystal. The micro-hardness near the fusion zone of Mg side is about HM 275–300. The brittleness phase with high hardness may be formed near the fusion zone. The fracture surface of Mg side shows a river pattern, which is a typical cleavage morphology. There are some hydrogen (H2) air holes in the fracture of Mg side.