The mechanism of localized corrosion in 2A97 aluminium alloy has been investigated. Electron backscatter diffraction analysis was performed at the localized corrosion site to determine the grain-stored energy. The relationship between the grain-stored energy, namely the population density of crystallographic defects, and the corrosion susceptibility of the alloy has been established. It was revealed that the grain boundaries that surrounded grains of relatively high stored energy were preferentially attacked. Intergranular corrosion could occur at grain boundaries where second phase precipitate was absent. Non-uniform attack of the adjacent grain interior was also observed along the attacked grain boundary, with preferential dissolution of the grains with high stored energy.
A correlation has been revealed between the localised corrosion susceptibility and the grain stored energy in AA2099-T8 aluminium alloy, with grains of higher stored energy being relatively more susceptible to corrosion attack. The grains of high stored energy contain increased crystallographic defects, which could consequently decrease their corrosion resistance. Additionally, since crystallographic defects are preferential sites for the precipitation of T 1 (Al 2 CuLi) phase, it is suggested that grains of high stored energy could also contain increased volume fraction of T 1 phase after aging, which might further increase corrosion susceptibility due to the electrochemically high activity of lithium rich T 1 phase.
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