Evaluation of the stress corrosion cracking behaviour of damage-tolerant AlLi sheet using the slow strain rate testing technique

Slow strain rate tests were performed on longitudinal tensile specimens of 8090-T81 sheet under permanent immersion conditions in various synthetic environments. Strain rates were in the range 10−7−10−4 s−1. Environmentally assisted cracking is observed in aqueous chloride-carbonate-hydrogencarbonate solutions. Near neutral 3.5% NaCl solution and also 3% NaCl solution with hydrogen peroxide added do not promote stress corrosion cracking with 8090-T81 alloy sheet. The degradation of ductility found with tensile specimens immersed in the latter corrosive environments is caused by localized corrosion independent of stress. Fracture energy data obtained from slow strain rate tests in substitute ocean water reveal a large scatter. Again, the deterioration observed is not related to stress corrosion cracking. Slow strain rate tests were also carried out with longitudinal tensile specimens of 2091-T8X and 2091 CPHK-T8X alloy sheet using an aqueous solution of 3% NaCl + 0.3% H2O2. For the alloy 2091 CPHK-T8X, similar results were obtained to those with 8090-T81, whereas 2091-T8X sheet is prone to environment-induced cracking in the aqueous chloride-peroxide solution.