Effect of Aging Time on Stress Corrosion Cracking Susceptibility of Al-3.88Cu-1.18Mg-0.31Mn Alloy

The stress corrosion cracking( SCC) performance of aluminum alloy Al-3. 88Cu-1. 18Mg-0. 31 Mn in T6 temper was investigated by using slow strain rate tension,optical microscope,scanning electron microscope and transmission electron microscope. The results show that the stress corrosion cracking susceptibility of the alloy reduces gradually with the increase of aging time. Stress corrosion cracking has positive correlation with intergranular corrosion,whose essence is that the potential difference between grain and grain boundaries produces galvanic corrosion and results in continuous grain boundary corrosion under stress.During aging,the S'( S) precipitates of grain boundary changed from continuous distribution gradually to discontinuous distribution,the precipitates of grain changed from GPB zone gradually to S'( S) phase and PFZ produced. These microstructural transformation make the stress corrosion cracking sensitivity of the alloy decreased with aging proceed.