Influence mechanism of cooling strategy on the improvement of corrosion performance of fine-grained Al7075 friction stir welding joint

Abstract

This work examines the microstructure and corrosion properties of fine-grained Al7075 across different regions under varying cooling conditions during friction stir welding. The findings demonstrate that forced cooling significantly improves the corrosion resistance of the welded joints. Specifically, the corrosion resistance was the highest in the stir zone, followed by the thermo-mechanical affected zone, and then the heat affected zone. Forced cooling mitigates grain growth by controlling the welding thermal effects, thereby increasing the proportion of Σ3 grain boundaries. The modification of these microstructural characteristics promotes the formation of a dense oxide layer, thereby enhancing the corrosion resistance. Furthermore, forced cooling mitigates the precipitation and coarsening of the anodic phase in the stir zone, which in turn reduces the susceptibility of the joint to pitting corrosion. Additionally, the lower recrystallization texture content in the joint, resulting from forced cooling, contributes to a reduction in the number of corrosion-active sites, thereby further improving the corrosion performance of the welded joint.

Keywords

friction stir welding / forced cooling methods / microstructure / corrosion performance

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