Research On Microstructure And Properties Of Laser Welding Brazing Joints Of Aluminum/Galvanized Steel Based On Different Al-based Filler Wires

Under the general trend of advocating"energy conservation and emission reduction",the automobile industry has proposed the concept of lightweight vehicles,using aluminum alloys to replace low-carbon steel and high-strength steel becomes more familiar.Laser welding is considered to be the safest and the most effective method to achieve aluminum-steel connection in the industrial field due to its high efficiency,low heat input,good welding shape,and more features.At the same time,a lot of researches show that using filler wires has a significant impact on the welding performance of the joint of aluminum and steel.However,few research has been done on the effect of Al-Si filler wires on the formation of various intermetallic compounds at the aluminum-steel welding interface.Therefore,this article will mainly illustrate these,and analyze the influence mechanism of Si on the Fe-Al interface layer.In this paper,ER1050,AlSi₅,Al Si₁₀ and AlSi₁₅ filler wires with a diameter of1.2mm are selected.Firstly,several sets of single-factor experiments are performed to establish a welding process window,and a set of optimal process parameters is determined for repeatable experiments.Weld formations,microstructures and mechanical properties of laser welding of aluminum alloy and galvanized steel are all studied in details.As the Si content in the wire increases,the layered IMC structure becomes thinner first and then thicker,and the continuous Fe Al structure at the bottom is broken into particles,in the meanwhile,the number of needle-like IMCs increases,and the growth directions gradually parallel the brazing interface.The Si atoms are mainly concentrated at the bottom of the layered IMC,and are enriched at the edge of the needle-shaped IMC in the form of?₅-Al_7.2Fe_1.8Si.For different types of IMC,combined with the thermal cycle curves and thermodynamic analysis of the welding process,the effect mechanism of Si on the growth of IMC is expounded,and the correlation between the atomic diffusion of aluminum-steel dissimilar joints and the growth process of intermetallic compounds is clarified.Finally,the influence mechanism of Si on the mechanical properties of joints is analyzed:The first is to improve the Fe Al phase that is originally harmful to welded joints by providing a heterogeneous core.The second is to form Fe₂(Al,Si)₅ by occupying the Fe₂Al₅lattice so that soften the layered IMC.The third is to produce?₅-Al_7.2Fe_1.8Si by peritectic reaction,and the acicular IMC is hardened by solid solution formation of Fe(Al,Si)₃.The fourth is to increase crystallization and the homogeneity of the two-phase particles to change the fracture mechanism of the joint during stretching process.Among them,the tensile performance of the joint under AlSi₁₀ is the best,and the tensile force is 1.622k N,which is 72.9%higher than that of ER1050 filler wire.