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

High alloyed beta-phase stabilized titanium alloys are known to provide comparable Young's modulus as that to the human bones (similar to 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 beta-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 beta-phase. The beta-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 beta-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 similar to 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 similar to 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. (C) 2015 Elsevier B.V. All rights reserved.