Microstructure, phase composition and mechanical properties of new, low cost Ti-Mn-Nb alloys for biomedical applications

Abstract A group of new Ti-7Mn-xNb alloys with Nb contents varying from 0 to 10 wt% were fabricated by conventional press and sinter powder metallurgy processing from blended elemental powders. The effect of Nb content on the sintering and phase stability as well as microstructure and mechanical characteristics of the alloys was investigated. Microstructural studies and phase analysis showed a two-phase microstructure composed of α and β phases in all alloys. However, addition of Nb up to 10 wt% enhanced the stability of the β phase hindering the transformation to α during furnace cooling and increasing the proportion of retained β. Sintering and densification of the Ti-7Mn-xNb alloys was enhanced by the fast diffusing Mn and negatively impacted by the slow diffusing Nb due to the reliance of solid sintering processes on diffusion. Nonetheless, the relative densities of the Ti-7Mn-xNb alloys with up to 10 wt% Nb were higher than that of the sintered CP-Ti. The compressive strength and hardness of the alloys varied in the range of (1842–2127 MPa) and (341–375 Hv) respectively. It was also observed that with increasing Nb contents, the elastic modulus decreased, while compressive strain increased due to stabilisation of a greater proportion of the β phase. The results showed that the low-cost Ti-7Mn-xNb alloys possess superior properties to those of CP-Ti and a number of other Ti based alloys developed for biomedical implant applications.