Room-Temperature Mechanical Properties of a High-Entropy Diboride


The mechanical properties of a (Hf,Mo,Nb,Ta,W,Zr)B2 high-entropy ceramic were measured at room temperature. A two-step synthesis process was utilized to produce the (Hf,Mo,Nb,Ta,W,Zr)B2 ceramics. The process consisted of a boro/carbothermal reduction reaction followed by solid solution formation and densification through spark plasma sintering. Nominally, phase pure (Hf,Mo,Nb,Ta,W,Zr)B2 was sintered to near full density (8.98 g/cm3) at 2000°C. The mean grain size was 6 ± 2 µm with a maximum grain size of 17 µm. Flexural strength was 528 ± 53 MPa, Young's modulus was 520 ± 12 GPa, fracture toughness was 3.9 ± 1.2 MPa·m1/2, and hardness (HV0.2) was 33.1 ± 1.1 GPa. A Griffith-type analysis determined the strength limiting flaw to be the largest grains in the microstructure. This is one of the first reports of a variety of mechanical properties of a six-component high-entropy diboride.


Materials Science and Engineering

Publication Status

Early View


Funding for the project was provided by GE Research under the project ‘‘Chemical Compatibility of Refractory High Entropy Alloys with Ultra-High Temperature Ceramics.”

Keywords and Phrases

Borides; Ceramic Engineering; Mechanical Properties

International Standard Serial Number (ISSN)

1744-7402; 1546-542X

Document Type

Article - Journal

Document Version


File Type





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Publication Date

11 Feb 2022