Influence of temper and surface condition on the exfoliation behaviour of high strength Al–Zn–Mg–Cu alloys

Exfoliation experiments were performed on two different 7000 series aluminium alloys in two different tempers and two different surface conditions according to ASTM G34 standard (EXCO test). The results of this experiment were evaluated with regard to surface condition, temper and alloy composition.The results after an EXCO test were evaluated according to the specification in the standard (in comparison to reference pictures), by visually ranking the samples, and by metallographic investigation. According to the ASTM standard, almost no changes could be seen with regard to the temper. Ranking and metallography revealed that AA7010 generally is less susceptible to exfoliation compared to AA7349. The differences between the temper conditions are not significant. It could be elaborated that the higher zinc content of AA7349 is detrimental for the exfoliation behaviour.