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<p>Poor fracture toughness remains a critical bottleneck that limits the engineering applications of high-entropy boride ceramics. In this study, (Cr<sub>0.2</sub>V<sub>0.2</sub>Ta<sub>0.2</sub>Ti<sub>0.2</sub>Nb<sub>0.2</sub>)B<sub>2</sub> high-entropy diboride ceramic composites with Ni contents of 10, 15, and 20&#xa0;wt.% were fabricated via boron–carbon thermal reduction and HPS (1600 ℃/2 h). The influence of Ni addition on the microstructure and mechanical properties was systematically investigated, and the underlying toughening mechanisms were thoroughly explored. Results indicate that the relative density of the composites increased with higher Ni content, reaching a maximum of 96.57% at 20&#xa0;wt.% Ni. Vickers hardness and flexural strength peaked at 26.4&#xa0;GPa and 349 MPa, respectively, with 10&#xa0;wt.% Ni, while the fracture toughness achieved an optimal value of 8.91&#xa0;MPa&#xa0;m<sup>1/2</sup> at 15&#xa0;wt.% Ni. High-temperature testing revealed that HEB-15Ni exhibited a ductile-to-brittle transition at 1000&#xa0;℃, with flexural strength and fracture toughness increasing to 462&#xa0;MPa and 9.6&#xa0;MPa·m<sup>1/2</sup>, respectively. Microstructural analysis indicated that Ni reacted with B to form the Ni<sub>2</sub>B secondary phase, creating submicron agglomerates. The Ni-B-based liquid phase generated during sintering significantly promoted material densification. Through mechanisms such as second-phase strengthening, crack deflection, and crack branching, this phase effectively enhances the fracture toughness of the material.</p>

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Mechanism of Ni Doping on the Preparation, Microregulation, and Mechanical Properties of High-Entropy Diboride Ceramic

  • 期刊论文

  • 发表日期：

    2026年5月23日

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  • Yaoqiang Tang,
  • Junhong Jia,
  • Runze Wei,
  • Rui Deng,
  • Congcong Zhao,
  • Xiaoyu Jiao,
  • Zekun Li,
  • Jie Yang,
  • Nairu He,
  • Haichao Zhao

摘要

Poor fracture toughness remains a critical bottleneck that limits the engineering applications of high-entropy boride ceramics. In this study, (Cr0.2V0.2Ta0.2Ti0.2Nb0.2)B2 high-entropy diboride ceramic composites with Ni contents of 10, 15, and 20 wt.% were fabricated via boron–carbon thermal reduction and HPS (1600 ℃/2 h). The influence of Ni addition on the microstructure and mechanical properties was systematically investigated, and the underlying toughening mechanisms were thoroughly explored. Results indicate that the relative density of the composites increased with higher Ni content, reaching a maximum of 96.57% at 20 wt.% Ni. Vickers hardness and flexural strength peaked at 26.4 GPa and 349 MPa, respectively, with 10 wt.% Ni, while the fracture toughness achieved an optimal value of 8.91 MPa m1/2 at 15 wt.% Ni. High-temperature testing revealed that HEB-15Ni exhibited a ductile-to-brittle transition at 1000 ℃, with flexural strength and fracture toughness increasing to 462 MPa and 9.6 MPa·m1/2, respectively. Microstructural analysis indicated that Ni reacted with B to form the Ni2B secondary phase, creating submicron agglomerates. The Ni-B-based liquid phase generated during sintering significantly promoted material densification. Through mechanisms such as second-phase strengthening, crack deflection, and crack branching, this phase effectively enhances the fracture toughness of the material.