Mechanical Characterization of ZrB2–SiC Composites with Varying SiC Particle Sizes
Flexural strength, elastic modulus, and hardness were used to characterize the mechanical properties of ZrB2–SiC composites that contained varying SiC particle sizes. Dense ZrB2–SiC
composites consisting of 70 vol% ZrB2 and 30 vol% α‐SiC were produced via hot pressing. This series of composites had maximum SiC
particle sizes that ranged from 4.4 to 18 μm. The mechanical properties scaled with the maximum SiC particle size, not with ZrB2 grain size. Flexural strength decreased as the maximum size
of SiC particles increased from 1150 MPa at 4.4 μm to 245 MPa at 18 μm with an abrupt decrease in strength at ~11.5 μm. Elastic modulus remained constant at ~530 GPa for compositions containing SiC
particles smaller than 11.5 μm, but exhibited a decrease with larger SiC particle sizes. Vickers and Knoop hardness were 21.4 and 17.2 GPa, respectively, for ceramics with SiC particle sizes <11.5 μm,
but hardness decreased for larger SiC particle sizes. The decreases in strength, elastic modulus, and hardness with SiC particles larger than 11.5 μm were coincident with stress‐induced microcracking
in the composites.