Stress corrosion cracking behaviour of laser treated aluminium alloy 7075 using a slow strain rate test

Abstract

The effect of excimer laser surface treatment on the stress corrosion cracking (SCC) behaviour of 7075 aluminium alloy was studied in a 3·5%NaCl solution using a slow strain rate test (SSRT). The test was conducted at the open circuit potential, a constant anodic or cathodic potential. The results of the SSRT and examination of the fracture surface of the specimens showed that the laser treatment can significantly increase the SCC initiation resistance of 7075 aluminium alloy, and reduce the degree of intergranular attack. This was due to the absence of coarse constituent particles and precipitate free grain boundaries in the laser melted layer. Moreover, the thin compact Al2O3 layer with nanocrystalline structures formed at the top surface of the laser melted layer serves as a barrier to retard corrosion attack.