Intrinsic crystallographic tuning: origin of superior plasticity in an oxygen-doped near-α titanium alloy

This study investigates an as-cast oxygen-doped near-α titanium alloy, developed via a kinetics-driven materials design strategy, that successfully overcomes the long-standing strength-ductility trade-off. Compared with the base alloy, the doped variant achieves a simultaneous enhancement in ultimate tensile strength (1178 MPa) and elongation (6.4%). Microstructurally, Oxygen doping induced the formation of a basketweave structure with significant hard-oriented microgeometry, where preferentially grown α-variants align their c-axes parallel to the tensile direction. The superior ductility is attributed to a dual-mechanism synergy. Intrinsically, inferred oxygen occupancy in tetrahedral sites triggers anomalous a-axis expansion and a significantly reduced c/a ratio , as macroscopically corroborated by systematic peak shifts and lattice parameter calculations in X-ray diffraction (XRD) analysis. This lattice distortion fundamentally lowers the Peierls barrier, activating pyramidal wavy slip. Extrinsically, The dislocation slip propagation behavior observed in adjacent α phases indicates that the addition of oxygen provides the interface with extremely high geometric compatibility(m'>0.7). This favorable interface matching can effectively alleviate local stress concentration and delay premature fracture, offering a novel pathway for designing high-performance titanium alloys.