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A multiphase high entropy diboride (Ti0.25Ta0.25Hf0.25Zr0.25)B2 was obtained by spark plasma sintering from a mixture of single-metal diborides. The as-prepared material at the microscale can be defined as a composite where grains of a Ta-rich/Ti-poor complex diboride phase are the reinforcement and grains of Ta-poor/Ti-rich complex diboride are the matrix. However, at the nanoscale, the grains are heterogeneous, composed of regions with a multitude of complex diboride compositions. The interface between nano regions is compositionally graded and has an irregular shape. The four-metal diboride shows a deformation-resistant mechanism under bending load. A strengthening process is active, increasing the room temperature bending strength (326 MPa) by ≈50 % at 1800 °C (488 MPa). A ductile behavior with a deformation strain of ≈7.5 % is observed at 2000 °C while bending strength (407 MPa) is ≈25 % above the value at room temperature. At 2000 °C, observation of dislocations propagating from one compositional nano region to another and with a different density suggests dislocation contribution, first of all, to plasticity. The peculiar heterogeneity of this material at nano and micro scales is considered the reason for the remarkable mechanical response to bending load at different temperatures.

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• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: high entropy diboride, high temperature bending test, microstructure, plasticity, spark plasma sintering

Date published: 2025-02-15

Publisher: Wiley-Blackwell

Journal:

• ADVANCED ENGINEERING MATERIALS (ISSN: 15272648) 2402723

Funding:

• Japan Society for the Promotion of Science KCB101 Enhancement of ultra-high temperature ceramics by amorphous phase formation
• NIMS AB3080 Polycrystalline Optical Materials Fundamental research for creating innovative optical materials

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5325

First published URL: https://doi.org/10.1002/adem.202402723

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Updated at: 2025-02-23 22:45:45 +0900

Published on MDR: 2025-02-23 22:45:47 +0900