Preparation and properties of (Hf_0.2Zr_0.2Ta_0.2Ti_0.2Me_0.2)B₂(Me=V, W) high entropy boride ceramics

In order to prepare high entropy boride ceramics with excellent performance, (Hf_0.2Zr_0.2Ta_0.2Ti_0.2Me_0.2)B₂(Me=V, W) high entropy boride ceramics were fabricated though boro/carbothermal reduction method combined with spark plasma sintering (SPS) in this paper. The effects of V and W on phase composition, morphology and mechanical properties of (Hf_0.2Zr_0.2Ta_0.2Ti_0.2Me_0.2)B₂(Me=V, W) high entropy boride ceramics were investigated. Results show that (Hf_0.2Zr_0.2Ta_0.2Ti_0.2Me_0.2)B₂(Me=V, W) high entropy boride powders are failed formed single-phase solid solution in 1600℃, but (Hf_0.2Zr_0.2Ta_0.2V_0.2Ti_0.2)B₂ is formed a complete solid solution after 2 000℃ sintering. However, WB phase is still detected in (Hf_0.2Zr_0.2Ta_0.2W_0.2Ti_0.2)B₂ sample. The density of (Hf_0.2Zr_0.2Ta_0.2V_0.2Ti_0.2)B₂(93.1%) is lower than that of (Hf_0.2Zr_0.2Ta_0.2W_0.2Ti_0.2)B₂(96.7%), but its grain size is smaller. The hardness of (Hf_0.2Zr_0.2Ta_0.2W_0.2Ti_0.2)B₂(24.0 GPa) is higher, but the fracture toughness is lower than that of (Hf_0.2Zr_0.2Ta_0.2V_0.2Ti_0.2)B₂ (3.32 MPa·m^1/2).