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.
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18 October 2021
Research Article|
October 19 2021
Transformation of metastable dual-phase (Ti0.25V0.25Zr0.25Hf0.25)B2 to stable high-entropy single-phase boride by thermal annealing
Special Collection:
Metastable High Entropy Alloys
Ana C. Feltrin
;
Ana C. Feltrin
1
Division of Materials Science, Luleå University of Technology
, 97187 Luleå, Sweden
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Daniel Hedman
;
Daniel Hedman
1
Division of Materials Science, Luleå University of Technology
, 97187 Luleå, Sweden
2
Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS)
, Ulsan 44919, Republic of Korea
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Farid Akhtar
Farid Akhtar
a)
1
Division of Materials Science, Luleå University of Technology
, 97187 Luleå, Sweden
a)Author to whom correspondence should be addressed: farid.akhtar@ltu.se
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a)Author to whom correspondence should be addressed: farid.akhtar@ltu.se
Note: This paper is part of the APL Special Collection on Metastable High Entropy Alloys.
Appl. Phys. Lett. 119, 161905 (2021)
Article history
Received:
August 12 2021
Accepted:
September 29 2021
Citation
Ana C. Feltrin, Daniel Hedman, Farid Akhtar; Transformation of metastable dual-phase (Ti0.25V0.25Zr0.25Hf0.25)B2 to stable high-entropy single-phase boride by thermal annealing. Appl. Phys. Lett. 18 October 2021; 119 (16): 161905. https://doi.org/10.1063/5.0066698
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