Investigation of microstructural match at friction welded TC17/TA19 interface based on β reconstruction under various frictional linear speeds

TC17 (α+β titanium alloy) and TA19 (near-α titanium alloy) are often joined in aerospace compressor rotors by rotary friction welding, but their differing phase transformation behaviors cause a mismatched microstructure at the weld interface. This study produced rotary friction welds at various linear speeds (0.65–2.60 m/s) to investigate how friction speed affects and controls the TC17/TA19 interface microstructure. EBSD mapping combined with β-phase reconstruction revealed the prior β grain structure at the weld interface. Finite element simulations provided interface temperature profiles, which were combined with reconstructed β grain size data to yield an empirical model linking friction speed with recrystallized β grain size at the interface. Increasing friction speed produced finer equiaxed β grains on both sides of the interface but slightly increased the TC17–TA19 microstructural mismatch. All joints exhibited high tensile strength (∼73–81 % of the weaker base metal's strength); however, a better microstructural match at lower friction speeds yielded significantly higher ductility (elongation ∼22–28 % vs ∼17–19 % at high speeds, up to ∼65 % improvement). These findings provide a quantitative basis for optimizing friction welding parameters to improve interface microstructural homogeneity, thereby enhancing the performance of dissimilar titanium alloy joints.