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Open AccessArticle

Electronic Origin of α″ to β Phase Transformation in Ti-Nb-Based Thin Films upon Hf Microalloying

1
Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina, Greece
2
Department of Physics, University of Ioannina, 45110 Ioannina, Greece
*
Authors to whom correspondence should be addressed.
Current address: Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China.
Current address: University of Cambridge, Department of Materials Science & Metallurgy, Cambridge CB3 0FS, UK.
Materials 2020, 13(6), 1288; https://doi.org/10.3390/ma13061288
Received: 20 February 2020 / Revised: 6 March 2020 / Accepted: 9 March 2020 / Published: 12 March 2020
(This article belongs to the Special Issue Ab Initio Study of Metallic Materials)
We present results on thin Ti-Nb-based films containing Hf at various concentrations grown by magnetron sputtering. The films exhibit α” patterns at Hf concentrations up to 11 at.%, while at 16 at.% Hf, the β-phase emerges as a stable structure. These findings were consolidated by ab initio calculations, according to which the α”–β transformation is manifested in the calculation of the electronic band energies for Hf contents between 11 and 18 at.%. It turns out that the β-phase transition originates from the Hf 5d contributions at the Fermi level and the Hf 6s hybridizations at low energies in the electronic density of states. Bonding–anti-bonding first neighbor features existing in the shifted plane destabilize the α″-phase, especially at high Hf concentrations, while the covalent-like features in the first neighborhood stabilize the corresponding plane of the β-phase. Thin films measurements and bulk total energy calculations agree that the lattice constants of both α″ and β phases increase upon Hf substitution. These results are important for the understanding of β-Ti-based alloys formation mechanisms and can be used for the design of suitable biocompatible materials. View Full-Text
Keywords: Ti alloys; β-phase; density functional theory; thin film; magnetron sputtering; X-ray diffraction; biocompatible materials Ti alloys; β-phase; density functional theory; thin film; magnetron sputtering; X-ray diffraction; biocompatible materials
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MDPI and ACS Style

Gutiérrez Moreno, J.J.; Panagiotopoulos, N.T.; Evangelakis, G.A.; Lekka, C.E. Electronic Origin of α″ to β Phase Transformation in Ti-Nb-Based Thin Films upon Hf Microalloying. Materials 2020, 13, 1288.

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