Stress corrosion cracking behaviour of excimer laser treated aluminium alloy 6013

The effect of excimer laser surface melting on the stress corrosion cracking behaviour of aluminium alloy 6013 has been investigated by means of a slow strain rate test at the open circuit potential, and at a constant anodic potential. After the laser treatment, a relatively thin non-dentritic re-solidified layer, of the order of a few micrometres, and largely free of coarse constituent particles, has been produced. At the top surface of the re-solidified layer, an oxide-nitride bearing film, having a thickness of a couple of hundred nanometres, is present. The results of the slow strain rate test in a 3.5%NaCl solution showed that, in terms of total displacement to failure and corrosion current density, the stress corrosion resistance of the alloy was greatly increased by excimer laser melting. The superior stress corrosion resistance of the laser-treated material is attributed to the laser-formed oxide-nitride top film acting as a barrier and retarding the initiation of cracks.