Synergistic Effects of Strength and Plasticity on the Wear Behavior of Thermomechanically Processed Ti–Nb Alloy

This work systematically investigates the tribological behaviors of a metastable β-type Ti–25Nb–3Zr–3Mo–2Sn alloy modified by multi-pass equal-channel angular pressing (ECAP) and subsequent aging treatment. The results demonstrate that multi-pass ECAP induces significant grain refinement, which synergistically enhances the strength, microhardness, and wear resistance of the alloy. With an increase in ECAP passes, the average COF and wear rate decrease progressively, accompanied by a distinct transition in the dominant wear mechanism—from severe adhesive and fatigue wear to mild abrasive wear. Short-term aging treatment (10 min) on the 1-pass ECAP sample achieves an optimal balance between strength and ductility, resulting in the lowest COF and wear rate among all tested conditions. Moreover, the wear behavior of the alloy is closely related to its ductility: when the elongation exceeds 10% (critical threshold), the wear process conforms to Archard’s law, with the wear rate showing a negative correlation with the alloy’s strength/hardness. In contrast, when the elongation falls below this critical value, brittle fracture dominates the wear process, leading to a sharp increase in the wear rate and a deviation from Archard’s law. This work not only clarifies the intrinsic relationship between mechanical properties and tribological performance of β-type titanium alloys but also provides a feasible thermomechanical processing strategy for the development of high-wear-resistance biomedical titanium alloys.