Correlations between stress corrosion cracking susceptibility and grain boundary microstructures for an Al-Zn-Mg alloy

The correlations between grain boundary precipitates (GBPs) area fraction and stress corrosion cracking (SCC) susceptibility for an Al-Zn-Mg alloy have been studied using TEM statistical investigations and image analysis. The results reveal that SCC susceptibility of the Al-Zn-Mg alloy first decreases and then increases with the increase of GBPs area fraction, which does not agree with Dix's anodic dissolution theory, suggesting that SCC of the Al-Zn-Mg alloy is dominated by hydrogen induced cracking when GBPs area fraction is relatively low and is dominated by anodic dissolution when GBPs area fraction is relatively high.