Study on the initiation stage of stress corrosion of an aluminum alloy using the subjective speckle technique

The aim of this paper is to investigate the initiation stage of stress corrosion of an aluminum alloy. Three-point bending experiments are carried out under displacement-controlled mode. The tested specimens are Al2024-T3 alloy with thickness of 2 mm which are immersed in the 3.5% sodium chloride solution in the experiments. The solution temperature was controlled from 20 to 80 °C and the exerted stresses were 0, 174 and 348 MPa, respectively, to study the influences of the temperature and the stress in the stress corrosion process. The subjective speckle method has been employed to observe the processes of the stress corrosion in microregions by means of measuring the local surface roughness of the specimens. Treatments of employing both average intensity and an autocorrelation coefficient of the subject speckle fields confirmed that the subjective speckle method is effective to characterize the stress corrosion initiation process of the tested aluminum alloy. The experimental results show that the temperature influences the rate of corrosion distinctly and meanwhile the rate of the corrosion also depends on the stress state considerably.