Abstract: To address the poor weldability of dissimilar aluminum-steel metals, red-blue composite laser welding technology was employed for butt welding of 1060 aluminum alloy and 316L stainless steel, and the effects of blue laser power on weld formation, interfacial microstructure, and mechanical properties were systematically investigated. The results showed that when no blue laser was applied, due to the significant difference in the absorption rate of infrared laser between aluminum and steel, undercutting and depressions appeared on the weld surface, with coarse needle-like FeAl₃ and layered Fe₂Al₅ formed at the interface. The intermetallic compounds(IMCs) layer had a large thickness and disordered distribution, and the joint tensile strength was only 6.22 MPa. After introducing 100 W blue laser, the aluminum side was fully melted, and the molten pool fluidity was enhanced, resulting in improved weld surface formation. The thickness of the IMCs layer was sharply reduced, and the brittle Fe₂Al₅ transformed from a continuous layered structure into discrete island-like morphology, with the simultaneous formation of continuous Fe₄Al₁₃. Consequently, the tensile strength of the joint increased to 53.22 MPa. However, excessively high blue laser power easily led to excessive melting of the aluminum side, causing shrinkage pores and re-thickening of the IMCs layer. These research results can provide experimental basis and theoretical support for the optimization of laser welding processes for dissimilar aluminum-steel metals.

Key words: aluminum-steel laser welding, blue laser power, intermetallic compounds, mechanical properties