Numerical investigation on dissimilar titanium-aluminum T-joints produced by Friction stir welding: process mechanics and material flow

Friction stir welding (FSW) is a renowned joining technology for creating difficult-to-be-welded or non-weldable dissimilar material joints engendering viscoplastic material flow at the interface. The present work compares the evolution of the material flow and properties during FSW of extremely different materials, viz., Aluminum alloy 6156 and commercially pure Ti Grade 2 with the help of numerical simulation and practical. The necessity of the appropriate heat flux to be achieved through balancing parameters was realized through simulation and experimental outcomes. In the paper, a numerical model is presented to predict the main field variables distribution and the resultant material flow during FSW of dissimilar Al-Ti skin stringer joints. Valuable insights relating to material flow patterns observed while altering the mutual skin stringer positions have been elaborated. Macrostructural and microstructural characterizations were carried out to understand the localized material microstructural evolution comprising grain refinement, intermetallic, defects, etc. The parametric influence on grain morphologies, intermittent phases, joint strengths, and hardness are discussed in depth. Interestingly, the joint strength values recorded for prepared T-joints are comparable with the ones found for butt joint configurations reported in the literature.