(1. 湖南大学 汽车车身先进设计制造国家重点实验室，长沙 410082；
2. 湖南大学 材料科学与工程学院，长沙 410082)
摘 要: 通过双相钢/铝合金有无添加Mn粉激光焊接的对比，揭示钢上、铝下激光搭接焊时Mn粉的作用。对焊接过程进行金属蒸气/等离子体形貌分析及光谱采集，发现添加Mn粉激光焊接时，金属蒸气/等离子体颜色明亮，光谱相对强度和金属蒸气/等离子体的电子密度增加；焊缝EDS分析发现，添加Mn粉时，熔池内部Fe、Al混合宽度减小，铝侧熔池两侧的Al含量增多；剪切试验发现，添加Mn粉焊接接头的平均抗剪强度提高，断口呈现混合断裂特征。由于添加Mn粉加快钢/铝层间热量传递，受热分解产生的金属蒸气在排出过程中，产生强烈向下的反冲作用力，使下层铝合金板材中的焊接匙孔加深，同时，金属蒸气改善下层铝合金的高反射率状况，促进铝合金吸收激光能量，导致焊接熔深增加。此外，熔池流动行为发生改变，下层Al向上层钢侧的扩散受到抑制，熔融态Al向熔宽两侧迁移，在减弱熔池内部Fe、Al混合程度、降低钢/铝界面Fe-Al化合物层厚度的同时，上、下板结合处的焊接熔宽加大，因此添加Mn粉改善钢/铝焊接接头的力学性能。
关键字: 激光搭接焊；钢/铝异种金属；Mn粉；焊缝成形
（1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,
Hunan University, Changsha 410082, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:Through comparison analysis of the laser welding of dual phase steel to aluminum alloy with and without Mn powder addition, Mn powder effect on dissimilar metals in steel-on-aluminum overlap configuration were discussed. By collecting and analyzing the metallic vapor/plasma shape and welding spectra, it is found that the color of metallic vapor/plasma induced by laser welding with Mn powder addition is bright, the relative intensity of spectra and electron density of metallic vapor/plasma increases. In addition, the mixing of Fe and Al in the molten pool decreases based on EDS analysis of joints, however, the content of Al on both sides of weld width increases. The results of the shearing experiments show that the average shear strength of welded joint increases compared to that without powder addition, and the failure mode is a mixed fracture. The welding keyhole of the lower Al plates becomes deeper by the reversed impact during the discharge of steam due to the decompose of Mn powder. Meanwhile, heat transfer between steel and aluminum is speeded up, the metallic vapor can decrease the reflectivity and increase the laser energy absorption of the lower aluminum alloy, thus, increasing the depth of the welding joints. What’s more, the flow behavior of the molten pool changes, the molten Al removes to both side of the welding joint, which leads to the width increase of the welding joints, thus the diffusion from the lower Al to the upper steel side is suppressed, and the size of Fe-Al intermetallic compound in aluminum/steel interface is reduced. Therefore, it can improve the mechanical properties of steel/aluminum welding joint with Mn powder addition.
Key words: laser lap welding; steel/l alloy dissimilar metal; Mn powder; weld molding
