Abstract：Al-Zn-Mg-Cu alloys were prepared by the traditional melt casting method. The effects of recrystallization and crystalline phase on the corrosion behavior of Al-Zn-Mg-Cu alloys were investigated through intergranular, exfoliation, stress, and electrochemical corrosion experiments, combined with characterization means such as metallurgical microscopy, scanning electron microscopy, and transmission electron microscopy. The results show that the Al-Zn-Mg-Cu-Zr alloy with lower degree of recrystallization and fewer residual crystalline phases has better corrosion resistance, the grade of exfoliation corrosion after 48 h of corrosion is EB, the time of stress corrosion crack initiation with bending tensile stress of 522 MPa is 30 min, and the rate of electrochemical corrosion becomes slower. The corrosion of ultra-high-strength aluminum alloy has three stages: at the early stage, pitting corrosion occurs around the residual crystalline phase (S phase) and the grain boundary precipitate phase (η phase); at the middle stage, pitting corrosion develops into intergranular corrosion along the high-angle grain boundary, and cracks are formed in the vicinity of the S phase and expand along the high-angle grain boundaries, leading to stress corrosion cracking; at the late stage, the expansion of corrosion products as well as the combined effect of intergranular corrosion and stress corrosion cracking trigger the exfoliation corrosion. The residual crystalline phase and recrystallization have a detrimental effect on its corrosion performance, the residual S phase in the matrix provides a site for corrosion to occur, and the η phase is continuously distributed on the high-angle grain boundaries formed by recrystallization, which provides a continuous channel for the expansion of intergranular corrosion and stress corrosion cracking.
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2024, Vol. 29 
