Effect of Ni/Si interlayer on microstructure and properties of laser welded aluminum/steel joints

The laser welding behavior of aluminum/steel dissimilar metal with Ni foil and Ni foil with Si powder as intermediate layer has been studied. The effect of Ni foil interlayer with Si powder at different power on the microstructure and properties of aluminum/steel dissimilar metals laser welded joints was investigated systematically. The results show that the tensile strength of the welded joint is obviously improved when the Ni foil with Si powder is added as the composite interlayer, the tensile strength of welded joint is increased to 1 307.96 N when the laser power is 2 150 W. The addition of Si powder increases the flowability of the molten pool, and changes the phase composition, element distribution and microstructure morphology of the aluminum/steel interface. Fe-Si and Al-Si binary phases were formed in the weld zone, which effectively suppressed the formation of Fe-Al binary brittle intermetallic compounds and improved the weldability of aluminum/steel. Therefore, the addition of Ni foil composite interlayer with Si powder can effectively improve the metallurgical reaction in the process of dissimilar metals laser welding of aluminum/steel, and then improve the mechanical properties of welded joints.