Synthesis of nanostructured biomaterials by high-pressure torsion: Effect of niobium content on microstructure and mechanical properties of Ti-Nb alloys

Titanium-niobium alloys with the bcc structure (β-Ti-Nb) are recently investigated for their potential use in biomedical applications; however, improvement of their mechanical properties (particularly hardness and elastic modulus) is still a challenge. In this study, nanostructured Ti-Nb alloys with different Nb contents were successfully synthesized by mechanical alloying of elemental powders via high-pressure torsion (HPT). The HPT process led to the homogenous mixture of the two elements and the formation of nanograined β phase. Examination of mechanical properties by nanoindentation and microhardness measurements revealed that all synthesized alloys exhibited high hardness and good plasticity; however, the best combination of low elastic modulus and high hardness was obtained for the sample with 25 at% Nb: E = 39 ± 11 GPa (close to the elasticity of human bone) and Hv = 3.7 ± 0.1 GPa (comparable to the hardest Ti-based biomaterials). The current results confirm the potential of HPT to synthesize nanograined Ti-Nb alloys for future biomedical applications.