Investigation of Microstructure, Mechanical Properties, and Numerical Modeling of Ti6Al4V Joints Produced by Friction Stir Spot Welding

In this work, lap-joined titanium alloy sheets have been successfully spot welded using friction stir spot welding (FSSW). Fully consolidated spot welds of thin Ti6Al4V sheets were obtained with a convex scrolled polycrystalline cubic boron nitride probe. The influence of processing parameters on FSSW was evaluated through a finite element analysis (FEA). Numerical results showed that von Mises stress and strain distributions were non-symmetric in the stir zone, whereas higher temperatures were observed in the region next to the tool pin. The welding microstructures showed different effects due to temperature gradients and material flow. The tool configuration played a significant role when determining the spot weld quality, since it directly influences the flow behavior of FSSW. It was observed that, in the stir zone, the microstructure suffered a transformation from α to β. The effect of welding parameters and the development of a FEA for the friction stir spot process were explored in the current investigation.