Influence of Retrogression and Reaging Treatment on Intergranular Corrosion Resistance and Exfoliation Corrosion Resistance in AA7010 Aluminum Alloy
Abstract
The aluminum alloys with zinc as the primary alloying element (AA7XXX series) exhibit high strength and are widely used as aircraft structural materials. These categories of aluminum alloys in their peak aging condition (T6) are known to be highly susceptible to general as well as stress corrosion cracking (SCC). Retrogression and reaging (RRA) treatment of this category of alloys leads to improvement in the corrosion resistance without significant compromise in strength. SCC was found to be improving in general in these alloys, but the intergranular corrosion (IGC) and exfoliation corrosion (EXCO) need to be evaluated. The effect of RRA heat treatment on the IGC and exfoliation of AA7010 aluminum alloy has been investigated and compared with T6 and T73 temper conditions of the alloy. The results indicate that the corrosion susceptibility of AA7010 aluminum alloy decreased by subjecting the alloy to multistage (RRA) heat treatment. It is attributed to the grain boundary precipitate coarsening and is also the major factor responsible for reducing the susceptibility to IGC and EXCO.