Effect of aging temperature on bimodal α microstructure and strength-ductility balance in TB6 titanium alloy after short-time solution treatment

The strength–ductility balance in Ti-10V-2Fe-3Al (TB6) titanium alloy depends critically on the bimodal α microstructure, which can be regulated by coupled solution and aging (SA) treatments. Here we report the combined effects of SA parameters on microstructural evolution and tensile properties. A short-time solution treatment (ST, 780 °C/0.5 h/WQ) retains a supersaturated β matrix while preserving a stable primary α (α p ) fraction of ~14.78 vol%. During aging, raising the temperature from 510 °C to 550 °C decreases the ultimate tensile strength from 1314.7 to 1124.8 MPa but improves elongation from 13.0% to 19.5%. This trend arises from a monotonic reduction in the secondary α (α s ) volume fraction (from 47.07% to 19.11%), which suppresses microvoid initiation and coalescence at α/β interfaces. The void volume fraction near the fracture surface drops from 0.72% to 0.05% as α s content decreases, indicating that precipitation density controls damage accumulation. At 530 °C, α p particles have the lowest aspect ratio (1.50), which may favor homogeneous strain distribution. The optimal treatment (780 °C/0.5 h/WQ + 530 °C/8 h/AC) therefore achieves a strength-ductility combination of σ UTS ≈ 1224 MPa and ε f ≈ 16.2%. These results link α s fraction and void evolution directly to macroscopic tensile response, which provide practical processing parameters for processing metastable near-β titanium alloys.