Improving the corrosion resistance of friction stir welding joint of 7050 Al alloy via optimizing the process route

The macro-galvanic effect in friction stir welding (FSW) joints is contributive for accelerating the localized corrosion of 7xxx aluminum alloy weldment. A process route, solid solution treating->FSW->T76 ageing (SSW-T76), was developed to weak the macrogalvanic effect. The microstructure and corrosion of joints prepared from SSW-T76 route and the conventional route (T76->FSW, T76W) were comparatively investigated. It was found that both precipitate coarsening and solute segregation were effectively suppressed when the route was changed from T76W to SSW-T76. The discrepancy in microstructure, micochemistry and corrosion potential between the base material (BM), the heat-affected zone (HAZ) and the nugget zone (NZ) was narrowed, leading to suppressed macrogalvanic effect and thereafter to decreased pitting and IGC.& COPY; 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The macro-galvanic effect in friction stir welding joints of 7xxx aluminum alloy promotes localized corrosion. A new process route, SSW-T76, was developed to weaken this effect. The microstructure, chemistry, and corrosion behavior of joints prepared via SSW-T76 were compared to those prepared via the conventional route (T76W->FSW, T76W). It was found that the SSW-T76 route effectively suppressed precipitate coarsening and solute segregation, leading to decreased macrogalvanic effect and reduced pitting and IGC.