Fabrication and properties of TiB2-based cermets by spark plasma sintering with CoCrFeNiTiAl high-entropy alloy as sintering aid

Equiatomic CoCrFeNiTiAl high-entropy alloy (HEA) fabricated by mechanical alloying (MA) was used as sintering aid for the densification of TiB2 by spark plasma sintering (SPS). The wettability between HEA and TiB2, the phases, microstructures and mechanical properties of the cermets were investigated. In the wetting analysis, excellent properties with a contact angle of 16.73° at 1420 °C was confirmed via sessile drop method. For the TiB2-based ceramics, no brittle phases can be detected in the XRD patterns. TEM observation revealed that there existed a narrow grain boundary between TiB2 and the HEA. A typical structure of HEA can be observed in the liquid phase. An optimized sintering temperature of 1600 °C was determined for the preparation of the TiB2-5 wt.% HEA ceramics with the combination of mechanical properties, including the relative density of 99.12%, the Vickers hardness of 2356 HV5 and the flexural strength of 800.2 MPa.