Stress corrosion cracking of a friction stir welded precipitation hardening aluminum alloy

The paper deals on the stress corrosion behavior of an AA 2024-T4 aluminum alloy friction stir welded. The results of previous works were summarized in which the effect of microstructural modification on the corrosion behavior of the alloy is evident. In the nugget, the re-crystallization of the alloy forms fine equiaxial grains, at the same time, the hardening precipitates are solubilized and reprecipitate in micrometric size at the grain border. In this zone stress enhanced intergranular corrosion was observed. Stress corrosion cracking was not detected in NaCl 0,6M solution both in constant load and slow strain rate tests, owing to the high generalized corrosion. In order to evidence stress corrosion effect, according to literature data, slow strain rate tests were carried out in air on specimens pre-corroded in the NaCl solution. These preliminary tests seem to permit to evidence some stress corrosion cracks in the nugget, but the preferential deformation of the heat affected zone, with the consequence of unloading of the most susceptible nugget zone masks the SCC effects.