Consumable-free dissimilar joining of Mg to steel using a laser-arc hybrid heat source

Abstract

Laser-arc hybrid direct lap welding offers an effective method for achieving high-performance welding of magnesium (Mg) alloys to steel. In this study, we optimized the mechanical properties of dissimilarly joined Mg and steel by controlling the offset of the laser heat source which directly affected the power delivered to the workpiece. We analyzed the variation of wetting angle and the mechanism of strengthening and tensile failure of the joints, with the results showing that under ideal processing conditions, the tensile strength of the direct lap welded joint without filler wire or any interlayers reached 295.7 N/mm, which is approximately 80% of the Mg alloy's nominal strength – an improvement that has not been previously reported in the literature. The laser improved the wettability of the joint and the laser keyhole played a critical role in pinning the weld seam, increasing the area of the interfacial reaction layer, and transferring the location of the crack source to strengthen the joint performance.