Microstructure of Mg₉₆Zn₂Y₂ alloy joint formed by resistance spot welding

Mg 96 Zn 2 Y 2 alloy sheets were welded by employing a resistance spot welding technique. The microstructures of the joint were observed and analyzed using scanning electron microscopy and transmission electron microscopy to investigate the difference between it and those of the base material. The joint comprises a base metal zone, heat-affected zone, fusion zone, and nugget. In the heat-affected zone, the dissolution of secondary phases occurred locally. In the fusion zone, the α -Mg grains were coarsened; and the secondary phase was transformed into a network distribution. In the nugget, the α -Mg grains were approximately 30 μ m in diameter; and most of the secondary phase possessed a long-period stacking-ordered structure of 18 periods rhombohedral lattice. The results reveal that the number of secondary phases and Mg 3 Zn 3 Y 2 compounds formed in the nugget were smaller than those observed in the base metal.