High Temperature Fatigue of Mild Steel under Varying Temperatures (2nd. Report)

Strained electrode reactions of 5083 aluminum alloy in 5.3% NaCl + 0.3% H_2O_2 aqueous solutions were studied as a function of tensile stress, strain, electrode potential, solution pH and grain boundary β precipitate by means of a constant strain rate method. An increase in rate of anodic dissolution was observed on application of plastic strain. The shape of the current / strain curves suggested that the anodic dissolution was controlled by the rate of oxide film rupture and by the subsequent rate of repassivation. The grain boundary with β precipitates was readily attacked at lower potential and by smaller strain than those when grain began to be attacked. Only at potentials higher than the breakdown potential, corresponding to oxide film rupture, of grain boundary stress corrosion cracking could occur. It was suggested that the susceptibility to stress corrosion cracking would depend on the difference in breakdown potential between grain boundary and grain.