Effect of SiC on densification, microstructure and mechanical properties of high entropy diboride (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2
Vasanthakumar Kombamuthu, Hakan Ünsal, Zdeněk Chlup, Monika Tatarková, Alexandra Kovalčíková, I. I. Zhukova, Naser Hosseini, Michal Hičák, Ivo Dlouhý, Peter Tatarko
Abstract
Highly dense high entropy diboride (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2-SiC composites with different β-SiC content (5, 10, 15, 20 and 25 vol.%) were synthesized using ball milling followed by Spark Plasma Sintering (SPS) at 1900°C. High-purity high entropy diboride (HEB) powder was synthesized using boro/carbothermal reduction of oxide precursors at 1800°C. X-ray diffraction patterns of the synthesized powders and sintered compacts of HEB showed a single solid solution with hexagonal AlB2 structure without any residual oxide impurities. X-ray energy dispersive Spectroscopy (EDS) mapping results indicated the uniform elemental distribution of transition metals in the HEB phase. The addition of SiC improved the densification of HEB-SiC composites. The composite with 20 vol.% SiC exhibited a unique combination of mechanical properties, such as superior Vickers hardness (22.28 ± 0.25 GPa), flexural strength (750. 21 ± 43.23 MPa), indentation fracture toughness (4.12 ± 0.2 MPa.m1/2), Young’s modulus (495.3 ± 0.3 GPa) and dynamic oxidation resistance (0.02 mg.cm-2.s-1).