High-entropy ceramics attract more and more attention in recent years. However, mechanical properties especially strength and fracture toughness for high-entropy ceramics and their composites have not been comprehensively reported. In this work, high-entropy (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta _0.2)B₂ (HEB) monolithic and its composite containing 20 vol% SiC (HEB–20SiC) are prepared by hot pressing. The addition of SiC not only accelerates the densification process but also refines the microstructure of HEB, resulting in improved mechanical properties. The obtained dense HEB and HEB–20SiC ceramics hot pressed at 1800 ℃ exhibit four-point flexural strength of 339±17 MPa and 447±45 MPa, and fracture toughness of 3.81±0.40 MPa·m^1/2 and 4.85±0.33 MPa·m^1/2 measured by single-edge notched beam (SENB) technique. Crack deflection and branching by SiC particles is considered to be the main toughening mechanisms for the HEB–20SiC composite. The hardness Hv_0.2 of the sintered HEB and HEB–20SiC ceramics is 23.7±0.7 GPa and 24.8±1.2 GPa, respectively. With the increase of indentation load, the hardness of the sintered ceramics decreases rapidly until the load reaches about 49 N, due to the indentation size effect. Based on the current experimental investigation it can be seen that the room temperature bending strength and fracture toughness of the high-entropy diboride ceramics are within ranges commonly observed in structure ceramics.

中文翻译：

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热压高熵二硼化物基陶瓷的机械性能

近年来，高熵陶瓷越来越受到关注。但是，尚未全面报道高熵陶瓷及其复合材料的机械性能，特别是强度和断裂韧性。在这项工作中，高熵（Ti _0.2 Zr _0.2 Hf _0.2 Nb _0.2 Ta _0.2）B ₂（HEB）单片及其包含20％（体积）SiC（HEB-20SiC）的复合材料是通过热压制备的。SiC的添加不仅加速了致密化过程，而且改善了HEB的微观结构，从而改善了机械性能。所得的致密HEB和HEB-20SiC陶瓷在1800℃热压后，其四点弯曲强度分别为339±17 MPa和447±45 MPa，断裂韧性为3.81±0.40 MPa·m ^1/2和4.85±0.33 MPa·。 m ^1/2通过单边切口光束（SENB）技术测量。SiC颗粒的裂纹偏转和分支被认为是HEB-20SiC复合材料的主要增韧机制。硬度Hv _0.2烧结后的HEB和HEB-20SiC陶瓷的比重分别为23.7±0.7 GPa和24.8±1.2 GPa。随着压痕载荷的增加，由于压痕尺寸效应，烧结陶瓷的硬度迅速降低，直到载荷达到约49N。根据当前的实验研究，可以看出高熵二硼化物陶瓷的室温弯曲强度和断裂韧性在结构陶瓷中通常观察到的范围内。