Microstructure evolution and its effect on the corrosion of dissimilar aluminum alloys friction stir welding joint

• Published in: Corrosion science 2023-08, Vol.220, p.111249, Article 111249
• Main Authors: Lu, Hongjian, Xu, Weifeng, Wang, Huan, Wang, Xian-Zong
• Format: Article
• Language: English
• Subjects: Corrosion; Dissimilar aluminum alloys joint; Friction stir welding; Galvanic corrosion; Microstructure evolution
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2023.111249

Microstructural heterogeneity in weld nugget zone (WNZ) of dissimilar AA7050-AA2024 friction stir welding joint and its effect on galvanic corrosion (GC) were explored. The increase in solid-solutioned Zn content and the number of intergranular MgZn2 greatly worsens the corrosion resistance of local AA7050-WNZ, while the grain refinement and fragmented Al2Cu slightly improves that of local AA2024-WNZ. The heterogeneous microstructure evolution lowers the GC resistance of global WNZ, causing the severest GC at WNZ-bottom with lowest resistance. The GC and intergranular corrosion synergistically promote the dissolution process. This work provides an insight on GC of dissimilar joint from microstructural heterogeneity. •More Zn-rich SSSS and MgZn2 GBPs deteriorate the corrosion resistance of AA7050 WNZ.•Grains refinement and fragment of Al2Cu improve the corrosion resistance of AA2024 WNZ.•The heterogeneous microstructure evolution promotes the galvanic corrosion in global WNZ.•Galvanic corrosion and intergranular corrosion synergistically accelerate the dissolution of joint.