The use of friction-surface processing as a method of corrosion protection of a friction-stir weld in the AL-LI-CU alloy AA2050-T851

Friction-surface processing (FSP) was explored as a possible method for mitigating corrosion of a friction-stir weld (FSW) in the Al-Li-Cu alloy AA2050-T851. The microstructure, hardness and corrosion behaviour of the base alloy, the FSW and the FSP regions was examined. The base alloy showed susceptibility to pitting parallel to the rolling direction and some intragranular corrosion, but no susceptibility to intergranular corrosion (IGC) or exfoliation corrosion. The FSW showed evidence of IGC in the nugget region and thermomechanically-affected zone (TMAZ), and exfoliation corrosion in the heat-affected zone (HAZ). Regions of the base alloy that had been treated by FSP also showed some IGC. Treatment of the FSW with FSP showed some indication of a reduction of IGC, and there was no evidence of exfoliation corrosion in the FSP-treated FSW-HAZ, but further work needs to be carried out to confirm this