Role of grain size on the stress corrosion cracking of 7475 aluminum alloys

The effect of grain size upon the stress corrosion cracking of 7475 Al-alloy plates has been investigated. Grain refinement resulted in a more homogeneous slip mode and a smaller size of grain boundary precipitates (GBPs) to influence the stress corrosion cracking (SCC) resistance. The more homogeneous slip mode is always beneficial for improving the SCC resistance. However, if the GBPs size was smaller than a critical precipitate size for nucleating hydrogen bubbles, the improvement of SCC resistance due to grain refinement, resulting from a more homogeneous slip mode, could not be obtained. The correlation of SCC susceptibility and hydrogen embrittlement susceptibility has been evaluated. The SCC susceptibility of the 7475 aluminum alloys is mainly controlled by hydrogen induced cracking mechanism.