Microstructures of laser–tungsten inert gas hybrid welding of dissimilar AZ31 Mg alloy and Q235 steel with Ni as interlayer

Abstract

Microstructures of a laser–tungsten inert gas (TIG) hybrid welding joint of dissimilar Mg alloy and steel with and without Ni interlayer are studied comparatively by SEM. The results show that there are a lot of precipitates of Mg17Al12 with mesh structures in the molten pool of Mg to steel dissimilar joints of laser–TIG hybrid welding without Ni interlayer, leading to the reduction in the mechanical properties of the welded joints. However, the addition of the Ni interlayer improves the microstructures of Mg to steel joints by laser–TIG hybrid welding. The precipitates in the molten pool are mainly composed of Mg2Ni and Mg17Al12 in the form of dispersive particles with the size of <5 μm. The shear strength of Mg to steel joints by laser–TIG hybrid welding with Ni interlayer is higher than that without Ni interlayer.