Investigation of grain boundary segregation evolution and corrosion behavior in 7050 aluminum alloy under oscillating laser melting

The weld structures of 7xxx series aluminum alloy have been applied on aerospace, rail transport, petrochemical engineering, and other fields. However, the corrosion resistance of welded joint is usually reduced due to the microstructure morphology of fusion zone (FZ). In this study, five oscillating modes were used to melt 7050 aluminum alloy, and the relationship between the microstructure and corrosion properties of different modes of FZ was analyzed. In particular, morphology observation, electron backscattered scattering detection (EBSD) test and phase analysis were carried out by SEM and TEM, and the grain boundary segregation, element distribution and grain characteristics under different modes were analyzed and compared. The relationship between laser beam oscillation mode, microstructure of FZ and corrosion resistance was established. It is concluded that the potential disparity between the precipitated phase and the grain, engendered by the variance in the concentration of the precipitated phase and the content of low-potential elements within the phase, exerts a decisive impact on the corrosion resistance of the material. The purpose of this study is to provide a new way to improve the corrosion resistance of 7050 aluminum alloy laser machined parts, and to meet the industrial needs of aerospace and other fields to the maximum extent. •Five laser modes were used to remelt 7050 aluminum alloy, and the macro and micro morphologies were compared.•The addition of oscillation mode effectively inhibited the generation of intergranular corrosion cracks.•The fusion zone of the circular oscillating laser sample has the best corrosion resistance.•The higher the content of low potential elements and their compounds in the phase, the more obvious the corrosion phenomenon.