Comparative study on Ti-Nb binary alloys fabricated through spark plasma sintering and conventional P/M routes for biomedical application.

The main purpose of this work is to obtain homogenous, single ß phase in binary Ti-xNb (x = 18.75, 25, and 31.25 at.%) alloys by simple mixing of pure elemental powders using different sintering techniques such as spark plasma sintering (pressure-assisted sintering) and conventional powder metallurgy (pressure-less sintering). Synthesis parameters such as sintering temperature and holding time etc. are optimized in both techniques in order to get homogenous microstructure. In spark plasma sintering (SPS), complete homogeneous ß phase is achieved in Ti25at.%Nb using 1300 °C sintering temperature with 60 min holding time under 50 MPa pressure. On the other hand, complete ß phase is obtained in Ti25at.%Nb through conventional powder metallurgy (P/M) route using sintering temperature of 1400 °C for 120 min holding time which are adopted from the dilatometry studies. Nano-indentation is carried out for mechanical properties such as Young's modulus and nano-hardness. Elastic properties of binary Ti-xNb compositions are fallen within the range of 80-90 GPa. Cytotoxicity as well as cell adhesion studies carried out using MG63, osteoblast-like cells showed excellent biocompatibility of thus developed Ti25at.%Nb surface irrespective of fabrication route.

First principles theoretical investigations of low Young's modulus beta Ti-Nb and Ti-Nb-Zr alloys compositions for biomedical applications.

High alloyed ß-phase stabilized titanium alloys are known to provide comparable Young's modulus as that to the human bones (~30 GPa) but is marred by its high density. In the present study the low titanium alloyed compositions of binary Ti-Nb and ternary Ti-Nb-Zr alloy systems, having stable ß-phase with low Young's modulus are identified using first principles density functional framework. The theoretical results suggest that the addition of Nb in Ti and Zr in Ti-Nb increases the stability of the ß-phase. The ß-phase in binary Ti-Nb alloys is found to be fully stabilized from 22 at.% of Nb onwards. The calculated Young's moduli of binary ß-Ti-Nb alloy system are found to be lower than that of pure titanium (116 GPa). For Ti-25(at.%)Nb composition the calculated Young's modulus comes out to be ~80 GPa. In ternary Ti-Nb-Zr alloy system, the Young's modulus of Ti-25(at.%)Nb-6.25(at.%)Zr composition is calculated to be ~50 GPa. Furthermore, the directional Young's moduli of these two selected binary (Ti-25(at.%)Nb) and ternary alloy (Ti-25(at.%)Nb-6.25(at.%)Zr) compositions are found to be nearly isotropic in all crystallographic directions.