An ab initio study of the structural and mechanical alterations of Ti-Nb alloys

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Gutiérrez Moreno, José Julio
Papageorgiou, D. G.
Evangelakis, G. A.
Lekka, Ch. E.
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This article describes a systematic theoretical investigation of the role of Nb substitution on the structural and mechanical properties of Ti-Nb alloys. The aim is to understand the origin of the low-rigidity of some of these materials. This quality makes these materials suitable for metallic implants. The mechanical stability conditions in conjunction with the calculated elastic constants of Ti-Nb predict the destabilization of α′ and ω structures, while the β-phase can be stabilized for Nb content above 10 at. %. The evaluated Young's moduli (E) follow the sequence of Eω > Eα′ > Εα″ > Εβ, revealing high Eω and Eα′ values (greater than 120 GPa), while the Eβ value converges to approximately 87 GPa. The averaged E, estimated from a weighted average of Eω, Eα′, Εα″, and Εβ ab initio values, reproduces the experimental Ti-Nb Young's modulus w-shaped curve. Young's modulus surface reveals highly anisotropic E values for all Ti-Nb phases. Eβ exhibits values under 30 GPa along the [100] direction for Nb compositions larger than 12 at. %, suggesting that the orientational growth of a Ti-Nb alloy is important for the design of low-rigidity alloys, especially at small Nb concentrations. These results can be used as a guide for the design of novel low-rigidity alloys for biomedical applications.
Biomaterials , Titanium alloys , Phase stability , Biomaterials , Polycrystalline material , Titanium , Transition metals , Elastic stiffness , Poisson's ratio , Elastic modulus , Crystal structure , Phase transitions , Crystal orientation
Moreno, J. J. G., Papageorgiou, D. G., Evangelakis, G. A. and Lekka, C. E. (2018) 'An ab initio study of the structural and mechanical alterations of Ti-Nb alloys', Journal of Applied Physics, 124(24), 245102 (7 pp).
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