Laser welding-brazing characteristics of AZ31B/TC4 joint based on electroplated Cu interlayer

Electroplated Cu coating was adopted as an interlayer to enhance the welding quality of laser welded-brazed immiscible and nonreactive Mg(AZ31B)/Ti(TC4) dissimilar metals. The influence of laser power on Mg/Ti welding was investigated, and then the interfacial microstructure and joint mechanical properties were analyzed with various welding parameters. The results indicated that Cu coating can significantly promote wetting-spreading ability of molten filler on the base metals. The molten Cu was involved into weld seam and diffused far from the interface. With the laser power inereasing, the tendency of formation of Ti₃Al interfacial reaction layer was improved. At the same time the interfacial bonding between Mg and Ti was enhanced. The maximum tensile load of Mg/Cu coated Ti joint was 3 085 N with the laser power of 1 700 W, representing 76.2% joint efficiency with respect to the Mg base metal. With higher laser power, the fracture mode of joint changed into a partial interfacial fracture from a complete interfacial fracture.