镁合金/钢异种材料激光熔钎焊接头组织及成形调控

采用激光熔钎焊技术对AZ31B镁合金与Q235钢进行异种金属搭接实验。添加Ni中间层协调镁合金与钢的冶金连接，通过外加纵向交变磁场调控接头成形及组织，以期提高接头的力学性能。结果表明：添加Ni中间层后接头类熔焊区IMC层为树枝状或连续纳米级层状AlNi相，实现冶金连接。外加交变磁场后Fe-Ni固溶体厚度减小且延伸进镁侧焊缝中，沟壑状的Fe-Ni固溶体增加了界面的结合面积。通过测量发现接头实际界面连接长度与拉剪线载荷有很大的联系。外加交变磁场后激光熔钎接头实际界面连接长度与拉剪线载荷随着磁场强度的增加呈现先增大后减小的趋势。当激光功率P=1250 W，焊接速度v=20 mm·s^-1，磁场强度B=10 mT，磁场频率f=35 Hz时，添加Ni中间层协调镁合金与钢的冶金连接，外加纵向交变磁场优化接头焊缝成形，接头拉剪线载荷最高，达到163 N/mm。

Microstructure and forming control of laser welding-brazing joint of magnesium alloy and steel dissimilar materials

The laser welding-brazing technology assisted by alternating magnetic field was adapted to AZ31B and Q235. In order to improve the mechanical properties of the joint, Ni interlayer was added to coordinate the metallurgical connection between magnesium alloy and steel, longitudinal alternating magnetic field was applied to optimize the weld forming. The results show that the IMC layer of the joint in fusion welding zone assisted by alternating magnetic field with Ni interlayer is composed of dendrite or continuous nanoscale layered AlNi phase. Magnesium alloy and steel realizes metallurgical connection by laser welding-brazing. The thickness of Fe-Ni solid solution decreases and extends into the weld of magnesium side after the application of alternating magnetic field, and increases the interface bonding area increases by the gully like Fe-Ni solid solution. The actual interface connection length is the main factor affecting the tension shear line load of the joint. The actual interface connection length and the tension shear line load of the welding-brazing joint exhibit first increasing and then decreasing trend as the increase of the magnetic field intensity (B). When the laser power P=1250 W, welding speed v=20 mm·s^-1, B=10 mT, frequency f=35 Hz, magnesium alloy and steel are able to achieve the metallurgical connection by the addition of Ni interlayer and the weld forming of the joint is optimized by applying longitudinal alternating magnetic field, the tension shear line load of the joint is the highest, reaching 163 N/mm.