Microstructure and corrosion resistance of 7075 aluminum alloy welded by TIG

In this paper, the self-developed 7075 aluminum alloy welding wire was used to conduct welding experiments on the 7075 aluminum alloy plate, and the effect of welding current (160-180 A) on the microstructure and corrosion resistance of the weld was studied, and the changes in performance after T6 heat treatment (480 ℃+1 h, 120 ℃+24 h) were observed. The microstructure at the weld is uniform isoaxial crystals, and with the increase of the current, the grain size continues to increase, and the grain boundary narrows after heat treatment, which is obviously seen to be less precipitation; XRD and SEM detection found that the weld is mainly composed of β phase (β-AlCu₃), η phase (MgZn₂) and a small amount of AlCuMg phase, and at the same time, Al₁₃Fe₄ intermetallic compounds and a small amount of Mg₂Si were detected; after heat treatment, the solid solution of alloying elements dissolved into the matrix, and no common reinforced phase was precipitated after aging. Only Al₁₃Fe₄, Mg₂Si and a small amount of Al₅Fe₃ and SiO₂ impurity phases were found. Through heat treatment, the elements are severely segregated before heat treatment to uniform distribution after heat treatment, reducing the self-corrosion potential at the weld; at the same time, the impedance and phase angle are improved, and the best corrosion resistance is the weld under the current 165 A after heat treatment.