Friction Stir Welding of AA2099-T83 and AA2060-T8E30 Aluminium Alloys with New Cr-Free Surface Treatments and Sealant Application

The feasibility for friction stir welding (FSW) surface-treated AA2099-T83 aluminium extrusions with AA2060-T8E30 aluminium sheets in the overlap configuration and using a sealant at the interface was investigated in this work. New Cr-free surface treatments such as thin film sulphuric acid anodising (TFSAA) and sol-gel were applied to the parent materials, and a sealant was applied before applying the FSW process. FSW welds were produced using several combinations of surface treatments and sealant application with no significant influence on FSW process stability and performance. The metallographic examination of the welds showed that a good protection of the crevice was achieved with some sealant accumulation at the edges of the overlapping region. The microstructural analysis showed no sealant remnants but the presence of some oxide remnants in the stir zone (SZ) of the welds, especially in the TFSAA treated parent material cases. However, these remnants did not show any significant effect in the static pull-out strength of the joints and failures at the most stressed zone of the AA2099-T83 extrusions outside the FSW weld region were consistently obtained.