Influence of Cr content on sintering, textured structure, and properties of (Hf, Zr, Ta, Cr, Ti)B2 high-entropy boride ceramics

Abstract

In order to provide insights into the influence of Cr content on the microstructure and corresponding properties of (Hf, Zr, Ta, Cr, Ti)B2, the effects of 10 at.% to 30 at.% Cr contents on texture development, phase composition, microstructure, and mechanical properties of (Hf, Zr, Ta, Cr, Ti)B2, which were prepared via a combination of boro/carbothermal reduction and SPS, were investigated in this study. The results showed that (Hf, Zr, Ta, Cr, Ti)B2 added with 15 at.% Cr content samples formed a textured microstructure due to the formation of CrB in the (Hf, Zr, Ta, Cr, Ti)B2 high-entropy boride powder. With the increase of Cr content up to 30 at.%, the density, grain size, and fracture toughness of (Hf, Zr, Ta, Cr, Ti)B2 high entropy boride ceramics increased, then for higher content, they decreased, and tended to remain constant. The hardness of (Hf, Zr, Ta, Cr, Ti)B2 decreased with the increase of Cr content. The (Hf, Zr, Ta, Cr, Ti)B2 with 15 at.% Cr content possessed the best comprehensive mechanical performance (Hv0.2: TS:26.9 ± 0.8 GPa, SS: 26.5 ± 0.6 GPa; KIc: TS:4.21 ± 0.46 MPa·m1/2, SS: 3.16 ± 0.18 MPa·m1/2) due to a combination of high relative density and unique textured structure.