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Strength of single‐phase high‐entropy carbide ceramics up to 2300°C
Author(s) -
Feng Lun,
Chen WeiTing,
Fahrenholtz William G.,
Hilmas Gregory E.
Publication year - 2021
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.17443
Subject(s) - flexural strength , materials science , composite material , relative density , ceramic , fracture toughness , grain size , carbide , vickers hardness test , dislocation , hot pressing , microstructure
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.