Comparative study of corrosion susceptibility and microstructural effects on AA7075-T6 aluminum alloys under different heat treatments

Al-Zn-Mg-Cu alloys of the 7xxx series have superior strength in their maximum aging condition (T6) compared to other age-hardenable aluminum alloys. Here, a comparative study of the corrosion susceptibility of AA7075-T6 aluminum alloys was performed under two heat treatments. A 5% NaCl salt solution at a temperature of 40 & DEG;C and neutral pH in the salt spray chamber was used to evaluate the microstructure and corrosion behavior of the aluminum alloy. The samples underwent two heat treatments; one included quenching solution using heat treatment at 475 & DEG;C, and the other included aging for 4 days. Several tests such as Vickers hardness test, optical microscope, SEM, as well as tensile test were used to study the characteristics of this alloy. The surface characteristics, including refined microstructure and residual stresses, were characterized, and their effect on localized corrosion was studied. The maximum strength value of the sample that underwent aging decreased by 24.85%, yet an increase was noticed for elongation of 18%. Pitting was more severe for the quenching treatment than for the aging and control treatments. This could be attributed to the formation of fine & eta;-phase precipitates that are fully coherent or partially coherent; the aging treatment improves the corrosion resistance due to the smaller size of the corrosion product after the specimen was etched in different areas.