Improved toughness of ZrB2–SiC composites with nanopowders obtained by mechanical alloying

In this study, the fracture toughness of ZrB2–SiC compoksites was enhanced by using nanopowders prepared by mechanical alloying. The phase compositions, microstructures, mechanical properties, thermal shock resistance, and oxidation resistance of the prepared ZrB2–SiC composites were systematically investigated. The results showed that the fracture toughness of ZrB2-20 vol% SiC and ZrB2-20 vol% Si2BC3N ceramics improved significantly to 7.80 MPa m1/2 and 8.21 MPa m1/2, respectively. The enhanced toughness was attributable to the toughening effects of in-situ developed BN and graphite plates, and prolonged crack propagation paths along the finer particles. In addition, the ZrB2-20 vol% Si2BC3N ceramics exhibited higher thermal stress resistance due to the zigzag propagation of cracks alongside the extended weak bonding interfaces. The presence of the in-situ developed BN and graphite plates contributed to the higher residual strength after thermal shock tests, where the residual stress was 113.2 MPa at a temperature difference of 1000 °C.
Source: Journal of Physics and Chemistry of Solids - Category: Physics Source Type: research