Exploring the probe offset window for dynamic support friction stir welding of Al/Ti dissimilar alloys

The probe offset window of dynamic support friction stir welding of AA6061 and TA2 dissimilar alloys was explored. Microstructures, interface formation, and mechanical properties of different Al/Ti joints were investigated. The defect-free joints were obtained at the positive probe offset from 0 to 0.4 mm, but a Ti-fragments group was formed in the SZ at the 0.4 mm offset distance. The diffusion layer was formed at the bonding interface but the IMCs layer was only formed over 0.2 mm probe offset, both TiAl and TiAl₃ phases were detected. The probe offset mainly affected interface temperature and interface formation mode, and hot extrusion and hot stirring models were proposed for interface formation. The hot extrusion model was suitable for the − 0.4 mm offset, while the hot stirring model was available for the other offsets. The minimum microhardness in the Al-HAZ had a similar value in the different probe offset distances. The range of 0–0.2 mm probe offset was more suitable for the Al/Ti DSFSW, and these joints had the HAZ fracture mode, which had average tensile strength values of 187 MPa and 188 MPa.