Modelling of phase equilibria in the Hf-V system below room temperature

• Published in: Journal of mining and metallurgy. Section B, Metallurgy Vol. 53; no. 3; pp. 239 - 247
• Main Authors: Vřesťál, J., Pavlů, J., Wdowik, U.D., Sob, M.
• Format: Journal Article
• Language: English
• Published: Bor Technical Faculty Bor, University of Belgrade 2017; Technical Faculty, Bor
• Subjects: Ab initio calculations; CALPHAD method; Energy; Equilibrium; Hf-V system; Intermetallic phases; Laves phase; Laves phases; Orthorhombic phase; Phase diagram; Phase equilibria; Phase transitions; Room temperature; Solid phases; Temperature; Zero Kelvin
• ISSN: 1450-5339; 2217-7175
• DOI: 10.2298/JMMB170704032V

Phase transformation from orthorhombic HfV2 structure to cubic C15 Laves
phase structure, which occurs during heating at about 114 K, is well known.
In this contribution, a thermodynamic description of this phenomenon is
provided supported by ab initio calculations. We utilize the third generation
of thermodynamic database extending the Scientific Group Thermodata Europe
(SGTE) unary data to zero Kelvin and demonstrate that it may be also applied
to intermetallic phases. The data from a recent thermodynamic assessment of
the Hf-V system (valid for temperatures above 298.15 K) were used and
extended to zero Kelvin by the same method as it was used for unary data.
Under the assumption of validity of harmonic approximation and electronic
contribution to the heat capacity, the thermodynamics of C15 and orthorhombic
phase were described. With the help of ab initio approach, we demonstrate
that the HfV2 orthorhombic phase and C15 Laves phase are mechanically stable
at 0 K and thanks to entropy stabilization they are in equilibrium with pure
element phases in the temperature region of structural change.
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