Overlap welding of magnesium AZ31B sheets using laser-arc hybrid process

This paper presents the results of recent investigations on the overlap weldability of magnesium alloy AZ31B sheets by laser-arc hybrid welding process. The effects of key welding parameters such as welding speed, defocusing distance, and laser-to-arc distance on overlap weldability of magnesium alloys sheets were analyzed, as well as the microstructure and properties of hybrid lap-welded joint. The results showed that sound overlap-welded joints of magnesium alloy AZ31B sheets without defects can be obtained. Among the welding parameters, defocusing distance and laser-to-arc distance were key factors to affect the penetration depth and bead shape. It also found that the cross-section of hybrid overlap-welded joint appears a “thumb pin” shape due to the characteristics of laser-arc hybrid welding. Hybrid overlap-welded joints can be divided into two parts: one was the zone of laser acting alone, while the other was the zone of laser and arc cooperation. Besides, it was concluded that the tensile shear strength of AZ31B overlap-welded by laser-arc hybrid welding was 80% comparable to those of base metal, and the corrosion resistance of weld bead was equivalent to that of base metal in 5 mol% NaCl solution.