Low-temperature fabrication and composition optimization of (Hf_0.2Zr_0.2Ta_0.2Ti_0.2Me_0.2)B₂-Ni (Me = Nb, W, V) composite materials with excellent mechanical properties

The high sintering temperature and poor fracture toughness of high-entropy diborides severely limit their applications. Moreover, there is a lack of relevant theoretical basis in composition design of high-entropy ceramics. In this work, a liquid-phase sintering mechanism was introduced by adding metal-based binders to prepare (Hf_0.2Zr_0.2Ta_0.2Ti_0.2Me_0.2)B₂-Ni composites at relatively low temperature (1550 ℃). The results indicate that when the Ni addition was 10 wt% and the holding time was 10 min, the flexural strength and fracture toughness of the samples reached 619 ± 68 MPa and 7.29 ± 0.32 MPa⋅m^1/2, respectively. Furthermore, The lattice constant difference factors for diborides corresponding to different elements were calculated. After replacing Nb with W and V elements, the lattice constant difference factor increased from 2.93 % to 4.01 % and 4.02 %, respectively, and the corresponding micro-Vickers hardness increased from 19.0 ± 1.4 GPa to 22.3 ± 1.9 GPa and 23.4 ± 0.7 GPa.