Welding pressure–controlled microstructural response at the TC17/TA19 friction-welded interface: insights from β reconstruction

Rotary friction welding (RFW) was employed to join dissimilar compressor alloys TC17 and TA19. To quantify how axial pressure governs the interfacial microstructure, Electron Backscatter Diffraction (EBSD) was combined with a parent-β reconstruction algorithm grounded in the Burgers orientation relationship. Tubular joints were produced at ~ 80, 120, and 160 MPa under fixed linear speed and burn-off. Increasing pressure refined dynamically recrystallized prior-β grains on both sides of the interface (TC17: ~ 3.40 → 3.27 → 3.01 µm; TA19: ~ 2.86 → 2.80 → 2.33 µm). In contrast, the TA19 α′-lamella thickness after cooling displayed a non-monotonic trend, peaking at ~ 0.73 µm at 120 MPa (vs ~ 0.54 µm at 80 MPa and ~ 0.49 µm at 160 MPa), due to the interplay between prior-β grain size and high-temperature dwell/cooling history. The intermediate pressure resulted in the best interfacial microstructural matching. Uniform equiaxed β grains were formed across the interface, while the α′ colonies on the TA19 side were moderately coarsened. This improved matching led to better tensile behavior, with a UTS of about 750–765 MPa and an elongation approximately 50% higher than that at 160 MPa. These results show that welding pressure can be used as an effective single-parameter approach to regulate interfacial microstructural matching in dissimilar titanium welds. In addition, β reconstruction provides a useful method for quantitative process–structure–property optimization in integrated TC17/TA19 rotors.