Mitigation Effects of Over-Aging (T73) Induced Intergranular Corrosion on Stress Corrosion Cracking of AA7075 Aluminum Alloy and Behaviors of Η Phase Grain Boundary Precipitates During the Intergranular Corrosion Formation

The stress corrosion cracking (SCC) behaviors of over-aged and peak-aged AA7075 aluminum alloys in a 5 wt% NaCl solution were compared. Even though the over-aging process induced intergranular corrosion (IGC), it decreased the SCC susceptibility of the material. Grain boundaries (GBs) with misorientation angles less than 30 degrees and the grain matrix were considered factors that reduced the IGC propagation rate, thereby preventing the development of SCC in the over-aged material. eta phase grain boundary precipitates (GBPs) underwent de-alloying, forming Cu-enriched particles during the IGC formation. However, the cathodic properties of these particles are not the key factors determining whether the IGC will occur or not.