Study on microstructure and corrosion resistance of an in situ Al₂O_3(p)/7075 alloy for automotive parts prepared by ultrasonic vibration

SiO₂ was added into 7075 alloys by ultrasonic vibration to form Al₂O₃ particles in situ. The microstructure, phase composition and corrosion resistance of the alloy were studied and analyzed by XRD, SEM, TEM, immersion corrosion tests and electrochemical tests, respectively. The results showed that ultrasonic vibration and in situ formation of Al₂O₃ particles could refine the microstructure of the alloy and disperse the agglomerated Al₂O₃ particles evenly, and Al₂O₃ particles could be used as the core of heterogeneous nucleation to improve the nucleation rate. The Al₂O_3(p)/7075 alloys with ultrasonic vibration are mainly composed of Al, Al₂O₃, Al₇Cu₂Fe, Al₂CuMg and Mg₂Zn phases. Compared with the 7075 alloys, its weight loss corrosion rate and hydrogen evolution corrosion rate decreased, the white corrosion products reduced, and the degree of pitting and intergranular corrosion weakened. The self-corrosion potential (E_corr) and pitting potential (E_p)increased, and the corrosion current density (I_corr) decreased. The improvement in the corrosion resistance of the Al₂O_3(p)/7075 alloy with ultrasonic vibration is due to the coordination of the slowing corrosion rate caused by microstructure refinement and the increase in corrosion potential caused by the in situ formation of Al₂O₃ particles.