Effect of Sintering Time on Mechanical Properties of (Hf-Ta-Zr-Nb-Ti)C

Advanced high-entropy (Hf-Ta-Zr-Nb-Ti)C ceramics were successfully fabricated by the combination of ball milling and a two-step sintering process at 2100 °C for 5, 10, and 20 minutes from commercially available powders. The microstructure characteristics and mechanical properties of the developed systems were investigated. The high-entropy ceramics exhibit: medium grain size from 8 μm to 11 μm, high compositional uniformity, and high relative density above 99.5 %. Vickers hardness for all systems decreased with increasing applied load, with the highest value HV1 = 22.0 GPa for the system sintered for 5 minutes, while the fracture toughness changed from 2.70 MPa.m^1/2 to 3.50 MPa.m^1/2. The highest four-point flexural strength of 284 MPa was measured for the system with the smallest grain size.