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 mo re homogeneous slip mode and a smaller size of grain boundary precipit ates (GBPs) to influence the stress corrosion cracking (SCC) resistanc e. The more homogeneous slip mode is always beneficial for improving t he SCC resistance. However, if the GBPs size was smaller than a critic al precipitate size for nucleating hydrogen bubbles, the improvement o f SCC resistance due to grain refinement, resulting from a more homoge neous slip mode, could not be obtained. The correlation of SCC suscept ibility and hydrogen embrittlement susceptibility has been evaluated. The SCC susceptibility of the 7475 aluminum alloys is mainly controlle d by hydrogen induced cracking mechanism. (C) 1997 Elsevier Science S. A.