Ab-initio and experimental study of phase stability of Ti-Nb alloys

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Gutiérrez Moreno, José Julio
Bönisch, M.
Panagiotopoulos, N. T.
Calin, M.
Papageorgiou, D. G.
Gebert, A.
Eckert, J.
Evangelakis, G. A.
Lekka, Ch. E.
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A systematic theoretical and experimental study concerning the crystallographic structure and electronic properties of Ti-xNb (x < 50 at%) alloys is presented, aiming to enlighten the electronic origins of the β-phase stability which is of high interest for the development of novel β stabilized Ti-based alloys for biomedical applications. Both quantum-mechanical calculations and X-ray diffraction found several structural phases depending on Nb concentration. The ab-initio total energy results reveal that at low Nb contents the α′ and ω phases are favoured while at Nb content >18.75 at% the β-phase is favoured against all other crystallographic structures in line with the experimental results. Interestingly, at high Nb content the α′ and ω hexagonal phases become unstable due to the electronic band filling close to the Fermi level EF, which is mainly due to Nb-p and Ti-d antibonding hybridizations. On the contrary, in the cubic β-Ti-25Nb (at%) the depletion of the occupied electronic states at the EF occurs mainly due to Nb-d and Ti-d bonding interactions, resulting in a stable β-TiNb structure. These data could enlighten the electronic origin of the Ti-Nb phase stability, thus, may contribute to the design of β stabilized low moduli Ti-based alloys suitable for load-bearing biomedical applications.
Biomaterials , Titanium alloys , Phase stability
Gutiérrez Moreno, J. J., Bönisch, M., Panagiotopoulos, N. T., Calin, M., Papageorgiou, D. G., Gebert, A., Eckert, J., Evangelakis, G. A. and Lekka, C. E. (2017) 'Ab-initio and experimental study of phase stability of Ti-Nb alloys', Journal of Alloys and Compounds, 696, pp. 481-489. 10.1016/j.jallcom.2016.11.231