A realization of Al/Ti dissimilar friction stir welding via bottom dynamic support using a Co-based alloy welding tool

The dissimilar Al/Ti joints were tentatively welded under different welding tools via dynamic support friction stir welding (FSW). The joint formation, intermetallic compounds (IMCs) layer, and mechanical properties of Al/Ti joint were investigated. The results showed that a Co-based alloy welding tool with a 15-mm shoulder diameter achieved the good external appearance and internal tissue. A diffusion layer with ~ 4 μm existed at the upper interface, while the diffusion layer at the lower layer was ~ 3 μm. Detrimental and continuous IMC layers were not generated at the Al/Ti interface, and root defects were avoided. This joint had the largest tensile strength of 189 MPa and fractured at the heat-affected zone (HAZ). The interface bonding, Ti fragments and hole defects in stirring zone, and the HAZ softening determined the ultimate fracture location. The dynamic support FSW offered a novel approach to achieve high-quality joining of Al/Ti dissimilar metals.