Friction Stir Welding of Dissimilar Al 5052 to Ti-6Al-4V Alloy with WC-Co Tool

The joining of dissimilar Al 5052 H32 and Ti-6Al-4V alloys was carried out by the friction stir welding (FSW) process using WC-Co and SKD61 tools. The microstructure, hardness distribution and tensile properties of those dissimilar joints have been investigated depending on welding variables and offset distance. The microstructures of base materials, weld nugget, heat affected zone (HAZ) and thermo-mechanical affected zone (TMAZ) were investigated by optical microscopy and scanning electron microscope. The effects of the rotation speed, welding speed, offset distance and rotation direction of the pin on the microstructure and tensile properties were investigated. The compositional microanalysis of the interface between Al and Ti was performed by electron probe micro analyzer (EPMA). The defects of dissimilar joints were evaluated by X-ray computed tomography (X-ray CT). The tensile strength and of the friction stir welded titanium and aluminium joints reached 212MPa representing 88% of the Al 5052 H32 alloy. The elongation of the FSW joint reached 9.1%. With increase in offset distance of the pin, tensile strength was decreased, and defects, Ti fragments and Ti oxide film were increased.