Preparation and characterization of diboride-based high entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2-SiC particulate composites

High entropy ceramics have attracted much attention in recent years, however, few open literature on the composites in which high entropy phases were used as matrix can be found. In this work, high entropy diboride powder was firstly synthesized, and then monolithic high entropy diboride ceramics of (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B-2 (sample HEB) and high entropy particulate composites of (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B-2-20 vol% SiC (sample HEB-SiC) were prepared by SPS at different temperatures. As-synthesized high entropy diboride powders demonstrated good sinterability in the temperature range from 1600 degrees C to 1900 degrees C. The grain growth rate of the high entropy phase was comparable to that in the ZrB2 system, but the addition of SiC second phase particles inhibited the grain growth of the high entropy diboride phase. Due to the grain growth inhibition by the introduced SiC particles, the hardness for the particulate composites increased. Moreover, the SiC particles improved the fracture toughness through crack deflection and branching.