Preparation of Novel (Hf_0.2Nb_0.2Ta_0.2Ti_0.2W_0.2) B₂ High-Entropy Boride Ceramics

In order to further improve the performance of high-entropy boride ceramics, a new type of high-entropy boride ceramics (Hf_0.2Nb_0.2Ta_0.2Ti_0.2W_0.2)B₂ was prepared by boro/carbothermal reduction combined with spark plasma sintering, and the effects of phase composition, microstructure and mechanical properties of high-entropy boride ceramics were studied. The results have shown that (Hf_0.2Nb_0.2Ta_0.2Ti_0.2W_0.2)B₂ high-entropy boride powder was dominated by the high-entropy phase at 1600°C, and that there were also W₂B₅ and HfB₂ phases After sintering at 2000°C, (Hf_0.2Nb_0.2Ta_0.2Ti_0.2W_0.2)B₂ high-entropy boride ceramics formed a homogeneous five-component solid solution. The relative density of the (Hf_0.2Nb_0.2Ta_0.2Ti_0.2W_0.2)B₂ ceramic was 92.3%, the fracture toughness was the 3.56 ± 1.04 MPa·m^1/2, and the hardness was 24.4 ± 1.5 GPa. This study broadened the high-entropy boride ceramic family and has laid a foundation for its performance improvement.