TY - JOUR

T1 - Ab-initio and experimental study of phase stability of Ti-Nb alloys

AU - Gutiérrez Moreno, J. J.

AU - Bönisch, Matthias

AU - Panagiotopoulos, N. T.

AU - Calin, Mariana

AU - Papageorgiou, D. G.

AU - Gebert, Annett

AU - Eckert, Jürgen

AU - Evangelakis, G. A.

AU - Lekka, Ch E.

PY - 2017/3/5

Y1 - 2017/3/5

N2 - 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.

AB - 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.

KW - Biomaterials

KW - Phase stability

KW - Titanium alloys

UR - http://www.scopus.com/inward/record.url?scp=84998879852&partnerID=8YFLogxK

U2 - 10.1016/j.jallcom.2016.11.231

DO - 10.1016/j.jallcom.2016.11.231

M3 - Article

AN - SCOPUS:84998879852

VL - 696.2017

SP - 481

EP - 489

JO - Journal of alloys and compounds

JF - Journal of alloys and compounds

SN - 0925-8388

IS - 5 March

ER -