Feasibility of using Ni₂₅Co₂₀Cu₁₀Fe₂₅Mn₂₀ high entropy alloy as a novel sintering aid in ZrB₂ ceramics

For the first time, Ni₂₅Co₂₀Cu₁₀Fe₂₅Mn₂₀ high entropy alloy (HEA) was employed as a sintering aid for fabrication of ZrB₂-based ceramics using spark plasma sintering (SPS) process. The mechanical properties, phase evolution, microstructural changes, and the densification mechanisms of ZrB₂-5 wt% HEA ceramics during the SPS step were scrutinized. The ZrB₂-5 wt% HEA ceramic, manufactured at 1900 °C, yielded interesting combination of properties, counting a relative density of 96%, a fracture toughness of 6.4 MPa m^1/2, and a hardness of 12.6 GPa. According to XRD patterns, there were ZrC and ZrO₂ phases with ZrB₂ matrix in the sintered samples. An unknown phase was also observed in the XRD patterns. Based on the history of the NiCoCuFeMn alloy and separation of Cu within the temperature range of 650–850 °C, that phase was related to CuB.