铜/镍箔中间层对铝/钢激光焊接接头组织与力学性能的影响

研究以Ni、Ni/Cu箔片为中间层的铝/钢异种金属激光焊接行为,系统考察Cu/Ni箔片复合中间层的添加对铝/钢异种激光焊接接头组织与性能的影响。利用扫描电子显微镜和能谱仪对焊缝横截面的组织形貌和各区域的元素分布进行观察分析,利用X射线衍射仪对焊接接头的主要物相进行分析,并利用电子万能试验机对焊接接头进行拉伸实验以表征其力学性能,结果表明:Cu/Ni箔片做复合中间层加入时,其中加入0.02 mm厚Cu箔片时焊接接头的最大剪切力提高至1754.72 N;加入0.05 mm厚Cu箔片时的最大剪切力为734.97 N,相比只添加Ni箔片时焊接接头的最大剪切力反而下降。Cu箔片的添加使得铝/钢界面的物相组成、元素分布和微观组织形态发生改变,同时增加了熔池的流动性。在靠近不锈钢侧的Fe-Al脆性相中的部分Fe原子被Cu原子取代生成新的二元韧性相,从而抑制Fe-Al二元脆性金属间化合物的生成,有效改善铝/钢的焊接性。因此,Cu/Ni箔片复合中间层的加入,可以有效地改善铝/钢异种激光焊接过程中的冶金反应,进而提高焊接接头的力学性能。

Effect of Cu/Ni foil interlayer on microstructure and mechanical properties of laser welded aluminum/steel joints

Laser welding of aluminum/steel dissimilar metals with Ni and Ni/Cu foils as intermediate layers was studied in this paper. The effect of Cu/Ni foil on microstructure and properties of dissimilar laser welded aluminum/steel joints was systematically investigated. Scanning electron microscope(SEM) and its own energy dispersive spectrometer(EDS) were used to observe and analyze the microstructure of the weld cross section and the element distribution in each area. X-ray diffractometer(XRD) was used to analyze the main phase of the welded joint, and tensile testing of welded joints using an electronic universal testing machine to characterize its mechanical properties. The results show that the tensile strength of the welded joint is greatly improved when Cu/Ni foil is added, compared with Ni foil as the interlayer only. The most obvious effect is that Cu foil with a thickness of 0.02 mm is added. The addition of Cu foil changes the phase composition, element distribution and microstructure of the aluminum/steel interface, and increases the fluidity of the molten pool. In the brittle phase of Fe-Al near the stainless steel side, some Fe atoms are replaced by Cu and Ni to form a new ternary ductile phase, which inhibits the generation of Fe-Al binary brittle intermetallic compounds and effectively improves the weldability of aluminum/steel. Therefore, the addition of Cu/Ni foil can effectively improve the metallurgical reaction in the process of aluminum/steel dissimilar laser welding, so as to improve the mechanical properties of welded joints.