Corrosion Control of Friction Stir Welded Aluminium Airframe Alloy

摘要

In the present study, microstructure and its influence on corrosion behaviour of friction stir welded aluminium airframe alloy have been investigated. Further, the effect of laser surface treatment on the microstructure and the corrosion behaviour was also assessed. The welded AA2024 alloy showed the expected zones associated with friction stir welding. Corrosion testing showed that modified microstructure reduced its corrosion resistance to localized corrosion, with the regions immediately outside TMAZ being most susceptible to corrosion. Laser treatment resulted in a melted near-surface layer, up to 5 (m thick, where normal constituent particles are absent. Scrutiny of the melted near-surface layer revealed continuous segregation bands, approximately 10 nm thick, containing mainly copper. Corrosion testing showed that laser treatment increases the short term resistance to localized corrosion due to the removal constituent particles. However, prolonged testing revealed corrosion within the melted near-surface layer and delamination of the melted near-surface layer from underlying bulk alloy. The corrosion is associated with copper rich segregation bands that promote local microgalvanic action.