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

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 1...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2021-01, Vol.104 (1), p.419-427
Main Authors: Feng, Lun, Chen, Wei‐Ting, Fahrenholtz, William G., Hilmas, Gregory E.
Format: Article
Language:English
Subjects:
Carbides
Ceramics
Density
Diamond pyramid hardness
dislocation
Dislocation density
Entropy
Flexural strength
Fracture toughness
Grain size
High temperature
high‐entropy carbides
high‐temperature flexural strength
Hot pressing
Mechanical properties
microstructure
Modulus of elasticity
Room temperature
Zirconium
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Summary: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·m1/2, 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.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.17443