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 (beta-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 beta phase. Examination of mechanical properties by nanoindentation and micmhardness 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.