Effect of Pre-Ageing Temperature on Microstructure Evolution, Mechanical and Corrosion Behavior of Rra Treated 7068 Aluminum Alloy

Mechanical and corrosion behavior of high-strength, high-zinc (> 7 wt%) containing 7068 aluminum alloy is investigated after employing different retrogression and re-ageing (RRA) treatments. Microstructural evolution after different RRA treatments is studied using DSC, STEM and SEM, and microstructural features are correlated with hardness and corrosion performance. Localized attack is manifested in the dissolution of second phase precipitates which occurs from selective leaching of magnesium and aluminum. Al 2 MgCu phase corroded severely as compared to Al 7 Cu 2 Fe precipitates. The combination of two opposite effects i.e., presence of nobler, high-copper grain boundary precipitates and micro-galvanic effect of precipitate-free zones govern the electrochemical behavior of RRA treated 7068 alloy