Abstract
High-strength 7068 aluminum alloy containing >7 wt% zinc deserves evaluation of its SCC performance in different ageing conditions, because of reported less effectiveness of over-ageing in newly developed high‑zinc 7xxx series alloys. Microstructural features resulting from different ageing treatments are correlated with mechanical properties, localised corrosion behaviour, and SCC susceptibility. Localised attack manifested in dissolution of second phase precipitates which occurs from selective leaching of magnesium and aluminum. The micro-galvanic effect of iron-containing precipitates on the matrix dissolution is less as compared to Al 2 MgCu phase. Peak and overaged alloy exhibited higher resistance to intergranular corrosion and SCC because of discontinuous grain boundary precipitates and fewer Al 2 MgCu/α-Al micro-galvanic couples. • Differently aged high-Zn 7068 alloy is characterized using DSC, XPS, SEM and TEM. • Peak aged condition showed intermittent distribution of GBPs. • Corrosion of 7068 alloy in different T6 temper conditions is compared. • Over-ageing is not necessary for satisfactory SCC performance in this alloy.
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