INCUBATION EFFECTS IN PRECRACKED STRESS-CORROSION SPECIMENS FROM AL-ZN-MG-CU ALLOY 7075

Corrosion tests in a buffered salt-chromate solution showed that crack growth in precracked double-cantilever beam (DCB) specimens from overaged 7075 alloy plate is subject to an initial incubation period. It is suggested that this effect is related to a transition barrier in which an intergranular stress corrosion crack develops from a predominantly transgranular precrack. This process involves a mixed mode of stress corrosion and mechanical rupturing of remaining ligaments. Evidence for transgranular stress corrosion was also found in the transition region between the precrack and the stress corrosion crack. © 1979.