Structural, mechanical and electronic properties of (TaNbHfTiZr)C high entropy carbide under pressure: Ab initio investigation

Yang, Yan; Wang, Wei; Gan, Guo‐Yong; Shi, Xuefeng; Tang, Bi‐Yu

doi:10.1016/j.physb.2018.09.014

Cited by 94 publications

(59 citation statements)

References 44 publications

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“…This has been attributed to the disorder associated with the multi‐metal composition . The modulus values of dense HECCs from the present study were similar to values reported in previous studies, which were in the range of 443 ± 40 GPa for experimental studies, and ranged from 456 GPa to 464 GPa in computational predictions.…”

Section: Resultssupporting

confidence: 90%

Low‐temperature sintering of single‐phase, high‐entropy carbide ceramics

Fahrenholtz

2019

J Am Ceram Soc

147

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Dense (Hf, Zr, Ti, Ta, Nb)C high‐entropy ceramics were produced by hot pressing (HP) of carbide powders synthesized by carbothermal reduction (CTR). The relative density increased from 95% to 99.3% as the HP temperature increased from 1750°C to 1900°C. Nominally phase pure ceramics with the rock salt structure had grain sizes ranging from 0.6 µm to 1.2 µm. The mixed carbide powders were synthesized by high‐energy ball milling (HEBM) followed by CTR at 1600°C, which resulted in an average particle size of ~100 nm and an oxygen content of 0.8 wt%. Low sintering temperature, high relative densities, and fine grain sizes were achieved through the use of synthesized powders. These are the first reported results for low‐temperature densification and fine microstructure of high‐entropy carbide ceramics.

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Section: Resultssupporting

confidence: 90%

Low‐temperature sintering of single‐phase, high‐entropy carbide ceramics

Fahrenholtz

2019

J Am Ceram Soc

147

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“…Vickers hardness increased from 24.4 ± 0.4 GPa for a load of 9.8 N to 25.0 ± 1.0 GPa for a load of 4.9 N. The hardness value of 24.4 ± 0.4 GPa at a load of 9.8 N in the present study was much higher than the values of 18.8 ± 0.4 GPa 13 and 16.2 ± 1.0 GPa to 17.1 ± 0.5 GPa 22 reported for same loads in previous studies, which can be F I G U R E 1 XRD pattern of (Hf 0.2 ,Zr 0.2 ,Ti 0.2 ,Ta 0.2 ,Nb 0.2 )C ceramics produced at 1900°C by HP attributed to the higher relative density and finer grain size of the HEC ceramics in the present study. Young's modulus values were 450 ± 5 GPa by ultrasound and 454 ± 5 GPa by bending, which were comparable to reported values of 443 ± 5 GPa from experimental studies, 17,25 and values of 456 GPa 26 and 464 GPa 17 from computational calculations. Both hardness and modulus values of HEC ceramics were higher than those values (23 ± 2 GPa 17 for hardness and 436 ± 30 GPa 17 for modulus) predicted using a volumetric rule of mixture (ROM) calculation based on the properties of the constituent binary carbides, presumably due to the effects of mass disorder and SS hardening described in other studies of high entropy ceramics.…”

Section: Room Temperature Mechanical Propertiessupporting

confidence: 87%

Strength of single‐phase high‐entropy carbide ceramics up to 2300°C

et al. 2020

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The mechanical properties of single-phase (Hf,Zr,Ti,Ta,Nb)C high-entropy carbide (HEC) ceramics were investigated. Ceramics with relative density >99% and an average grain size of 0.9 ± 0.3 µm were produced by a two-step process that involved carbothermal reduction at 1600°C and hot pressing at 1900°C. At room temperature, Vickers hardness was 25.0 ± 1.0 GPa at a load of 4.9 N, Young's modulus was 450 GPa, chevron notch fracture toughness was 3.5 ± 0.3 MPa•m 1/2 , and four-point flexural strength was 421 ± 27 MPa. With increasing temperature, flexural strength stayed above ~400 MPa up to 1800°C, then decreased nearly linearly to 318 ± 21 MPa at 2000°C and to 93 ± 10 MPa at 2300°C. No significant changes in relative density or average grain size were noted after testing at elevated temperatures. The degradation of flexural strength above 1800°C was attributed to a decrease in dislocation density that was accompanied by an increase in dislocation motion. These are the first reported flexural strengths of HEC ceramics at elevated temperatures. K E Y W O R D S dislocation, high-entropy carbides, high-temperature flexural strength, mechanical properties, microstructure How to cite this article: Feng L, Chen W-T, Fahrenholtz WG, Hilmas GE. Strength of single-phase high-entropy carbide ceramics up to 2300°C.

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“…They generally used the random solid-solution-model (RSSM) to evaluate their properties although the methods employed could be very different [13][14][15] . Current theoretical methods for HEAs are spread out and include but not limited to the use of CALPHAD 1,12,16 , quasi-random-structure (SQS) [17][18][19] usually in the framework of density functional theory (DFT) on small-size supercells 20 , coherent potential approximations (EMTO-CPA) or effective medium theory 21,22 . Despite a plethora of approaches and methods used, few of them can provide a comprehensive view on their formation and the prediction of their properties due to several obstacles.…”

Section: Introductionmentioning

confidence: 99%

Fundamental electronic structure and multiatomic bonding in 13 biocompatible high-entropy alloys

et al. 2020

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High-entropy alloys (HEAs) have attracted great attention due to their many unique properties and potential applications. The nature of interatomic interactions in this unique class of complex multicomponent alloys is not fully developed or understood. We report a theoretical modeling technique to enable in-depth analysis of their electronic structures and interatomic bonding, and predict HEA properties based on the use of the quantum mechanical metrics, the total bond order density (TBOD) and the partial bond order density (PBOD). Application to 13 biocompatible multicomponent HEAs yields many new and insightful results, including the inadequacy of using the valence electron count, quantification of large lattice distortion, validation of mechanical properties with experiment data, modeling porosity to reduce Young's modulus. This work outlines a road map for the rational design of HEAs for biomedical applications.

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Structural, mechanical and electronic properties of (TaNbHfTiZr)C high entropy carbide under pressure: Ab initio investigation

Cited by 94 publications

References 44 publications

Low‐temperature sintering of single‐phase, high‐entropy carbide ceramics

Low‐temperature sintering of single‐phase, high‐entropy carbide ceramics

Strength of single‐phase high‐entropy carbide ceramics up to 2300°C

Fundamental electronic structure and multiatomic bonding in 13 biocompatible high-entropy alloys

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