Transformation of metastable dual-phase (Ti0.25V0.25Zr0.25Hf0.25)B2 to stable high-entropy single-phase boride by thermal annealing
- 18 October 2021
- journal article
- research article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 119 (16), 161905
- https://doi.org/10.1063/5.0066698
Abstract
Transition metal borides have a unique combination of high melting point and high chemical stability and are suitable for high temperature applications (>2000 °C). A metastable dual-phase boride (Ti0.25V0.25Zr0.25Hf0.25)B2 with distinct two hexagonal phases and with an intermediate entropy formation ability of 87.9 (eV/atom)−1 as calculated via the density functional theory (DFT) was consolidated by pulsed current sintering. Thermal annealing of the sintered dual-phase boride at 1500 °C promoted the diffusion of metallic elements between the two boride phases leading to chemical homogenization and resulted in the stabilization of a single-phase high-entropy boride. Scanning electron microscopy, in situ high temperature x-ray diffraction, and simultaneous thermal analysis of the as-sintered and annealed high-entropy borides showed the homogenization of a dual-phase to a single-phase. The experimentally obtained single-phase structure was verified by DFT calculations using special quasirandom structures, which were further used for theoretical investigations of lattice distortions and mechanical properties. Experimentally measured mechanical properties of the single-phase boride showed improved mechanical properties with a hardness of 33.2 ± 2.1 GPa, an elastic modulus of 466.0 ± 5.9 GPa, and a fracture toughness of 4.1 ± 0.6 MPa m1/2.Funding Information
- Stiftelsen för Strategisk Forskning (RIF14-0083)
- Vetenskapsrådet (2018-05973)
This publication has 56 references indexed in Scilit:
- Refractory Diborides of Zirconium and HafniumJournal of the American Ceramic Society, 2007
- From ultrasoft pseudopotentials to the projector augmented-wave methodPhysical Review B, 1999
- Generalized Gradient Approximation Made SimplePhysical Review Letters, 1996
- Efficient iterative schemes forab initiototal-energy calculations using a plane-wave basis setPhysical Review B, 1996
- Projector augmented-wave methodPhysical Review B, 1994
- Ab initiomolecular dynamics for liquid metalsPhysical Review B, 1993
- Electronic properties of random alloys: Special quasirandom structuresPhysical Review B, 1990
- Special quasirandom structuresPhysical Review Letters, 1990
- The enthalpy of formation of solid borides, carbides, nitrides, silicides and phosphides of transition and noble metalsJournal of the Less Common Metals, 1981
- A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness: I, Direct Crack MeasurementsJournal of the American Ceramic Society, 1981