Abstract
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.
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