Influence of oxygen on microstructure, mechanical properties and deformation mechanism of spark plasma sintered Ti–Nb–Zr–Mn alloys

Herein, Oxygen-bearing Ti-Nb-Zr-Mn β titanium alloys were fabricated using a process that integrates mechanical ball milling with spark plasma sintering. A comprehensive analysis was performed to assess the influence of oxygen on the material’s microstructure, phase composition, mechanical properties, as well as deformation mechanisms. The incorporation of TiO 2 introduces oxygen atoms, which induce phase transformation and affect the mechanical behavior. With increasing oxygen levels, the elastic modulus and hardness exhibit an initial gradual rise, followed by a steep increase after reaching a certain level. Compared to the pristine alloy, higher oxygen levels lead to an increase in hardness and modulus but simultaneously reduce ductility and promote brittle fracture behavior. Meanwhile, the presence of oxygen inhibits deformation twinning and stress-induced martensitic transformation, while also modifying ω/α phase precipitation, resulting in a transition of the dominant deformation mechanism. To achieve an optimal balance among low elastic modulus, high strength, and acceptable plasticity in metastable β-Ti alloys, precise control of oxygen content is crucial. As a result, the optimized 0.2O alloy achieves a yield strength of 1056 ± 17 MPa, with only a slight reduction in plasticity to 14.8 ± 1.5%. This study offers valuable insights for designing novel metastable β Ti alloys that achieve an optimal balance between high strength and considerable ductility.