Without adding any interlayers or coatings, the lap welding experiment of AZ31B magnesium alloy and DP980 high-strength steel was performed with the laser-induced tungsten inert gas welding (TIG) arc technology. Through optimizing the process parameters, a high-quality lap weld joint was obtained. The effect of TIG arc current on the forming and mechanical properties of the joint was studied significantly. The results indicate that the wetting and spreading ability of magnesium alloy in high-strength steel is improved with the increase of arc current, which increases the weld width and reduces the wetting angle. Additionally, the maximum tensile load of magnesium alloy/steel welded joints increases first and then decreases with the increase of arc current and the fracture mode of the joint is changed from fracture along the interface to fracture along the weld. When the TIG current is 80 A and the laser power is 350 W, the maximum average tensile load of the welded joint reaches 279 N/mm.The increase of weld width, thickness of interfacial layer and pinning of laser keyholes together enhance the performance of magnesium alloy/steel joints.
Fig.8 不同电流下界面线扫描 (a)扫描方向示意图；(b)70 A；(c)80 A；(d)90 A
Fig.9 断裂模式示意图 (a)界面反应过程；(b)焊接接头；(c)拉剪后断裂；(1)50~70 A；(2)80, 90 A
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