Abstract
The corrosion properties of friction-stir-welded (FSW) AA7050-T7651 have been investigated. Immersion in a modified exfoliation corrosion (EXCO) solution showed that the grain boundaries in the nugget, partially recrystallized zone (PRZ), and heat-affected zone (HAZ) were sensitized. The most heavily sensitized region was the nugget/PRZ interface. Pitting potentials were determined potentiodynamically in 0.6 M sodium chloride (NaCl). The nugget had the lowest pitting potential, which was 75 mV less than the parent material. The pitting potential of the HAZ was 50 mV less than the parent material. In results from the slow strain rate test, the percent elongation in 0.6 M NaCl for the slowest strain rate used was ∼20% that in air, indicating susceptibility to stress corrosion cracking. Metallography showed that the fracture was intergranular and that the crack path was on the nugget side of the nugget/PRZ interface. Analytical electron transmission microscopy (ATEM) does not conclusively identify a grain boundary, precipitate-free zone, or precipitate chemistry, which correlates with sensitization. These chemistries are complex and vary with distance from the center line of the weld.
