胶层-镍箔辅助激光焊钢/镁接头组织与性能

采用钢板在上、镁板在下且添加胶层-镍箔辅助的激光焊接技术，对厚度1.4 mm的DP590双相钢和厚度1.5 mm的AZ31B镁合金进行焊接， 基于热力学计算选择添加箔片元素，分析接头焊缝形貌、显微组织与力学性能，并对接头熔池温度场和流场进行数值模拟. 结果表明，激光功率1 800 W，焊接速度30 mm/s，离焦量为 + 2 mm，流量为15 L/min的氩气保护的工艺条件下，添加镍箔实现了镁/钢冶金连接，同时添加胶层和镍箔，与单一添加镍箔相比，接头平均抗剪强度提高1.73倍；添加胶层，焊缝连续光滑， 镁侧熔池的熔化宽度增大，钢/镁横向结合面积增加，熔池温度梯度降低，熔池流动速度提高，促进了界面元素相互扩散和冶金反应，因此钢/镁接头性能得到大幅提升.

Microstructure and properties of steel/magnesium joint for adhesive layer-Ni foil assisted laser welding

DP590 dual-phase steel with thickness of 1.4 mm and AZ31B magnesium alloy with thickness of 1.5 mm were welded by adhesive layer-Ni foil assisted laser welding technology in an overlap steel-on-Mg configuration. Foil elements were selected based on thermodynamic calculation, weld morphology, microstructure and mechanical properties of the joint were analyzed, and the temperature field and flow field of molten pool were simulated. The results show that under the conditions of laser power of 1 800 W, welding speed of 30 mm/s, defocusing amount of + 2 mm and flow rate of 15 L/min, the metallurgical connection between magnesium and steel can be realized by adding Ni foil. While adding adhesive layer and Ni foil, the average shear strength of the joint is increased by 1.73 times compared with that of single Ni foil. The weld is continuous and smooth with the addition of adhesive layer, the melt width of magnesium side molten pool increases, the transverse bonding area of steel/magnesium increases, the transverse and longitudinal temperature gradient at interface decreases, the flow velocity of molten pool increases, and the element distribution uniformity is improved, which promotes the diffusion and metallurgical reaction of interfacial elements. Hence, the performance of the steel/magnesium joint is improved greatly.