Effect of Ni Foil on Laser Fusion Welding Microstructure and Mechanical Properties of SUS301L / 6061 dissimilar joints

The presence of brittle Fe-Al intermetallic compounds (IMC) limits the performance of steel / aluminum joints. In this paper, Ni foil will be used as an intermediate layer in SUS301L (Fe) / 6061 aluminum (Al) dissimilar overlap laser welding to suppress the generation of IMC at the Fe-Al interface. Explored the influence of Ni interlayer on joint strength, joint microstructure composition, and element distribution, and analyzed the effect of Ni foil in the welding process. The results of the composition and distribution of various elements in the weld microstructure indicate that the introduction of Ni foil significantly improves the phase composition of the brittle layer at the weld interface, forming NiAl/NiAl3 ductile phase compounds, indicating that the reaction between Fe and Al is suppressed. In addition, it was found that the thickness of Ni foil has a significant impact on the formation of Fe-Al IMC. After adding Ni foil with a thickness of 0.05mm, the maximum load value reached 498.03N. Compared to the situation without Ni foil, which one has increased by 47.45%. Through EDS testing of tensile fractures, it was found that the mechanical properties of the joint largely depend on the ductility/brittleness of IMCs.