Prediction of phase evolutions during friction stir welding of Ti-grade 5 T-joints using finite element modeling

Friction Stir Welding (FSW) is a solid-state welding technology pioneered by The Welding Institute (TWI) in 1991. Originally used to weld aluminum alloys, it is now effectively utilized to weld high-resistance materials as well. The ultimate mechanical characteristics of the joints are inextricably linked to the microstructural evolutions that occur during the process in terms of phase change. It is then crucial, in order to carry out an effective process engineering, to predict the final material microstructure determined by the thermal history that occurred during the process itself. In the paper, a 3D Finite Element Method (FEM) model for the FSW of T-joints is proposed, based on a thermo-mechanical staggered analysis, able to predict the phase transition of the Ti6Al4V alloy. The model, which has been fine-tuned using experimental data, can predict the phase volume fraction in the different joint zones. The acquired findings allow assessing the effectiveness of the FSW FEM model as a process design tool.