Microstructure and room-temperature mechanical properties of β sialon/SiC nanocomposites

Microstructure and room-temperature mechanical properties of two β sialon/SiC nanocomposites, one comprised 20 wt.% β SiC nanoparticle and the other comprised 40 wt.% β SiC nanoparticle (denoted as Sm20 and Sm40, respectively), were studied and compared with those of the monolithic (denoted as Sm0) in this article. The three-point flexural strength values were measured to be 747, 712 and 755 MPa for Sm0, Sm20 and Sm40, respectively, while the Vickers hardness values were 18.4, 16.3 and 17.1 GPa and the indentation fracture toughness values were 8.70, 6.83 and 8.71 MPa m^1/2 for Sm0, Sm20 and Sm40, respectively. Weibull modulus values on Vickers hardness were determined to be 39, 33 and 43, while those on fracture toughness were 19, 22 and 19 for Sm0, Sm20 and Sm40, respectively. The addition of SiC nanoparticles to the matrix Sm0 has little positive effect on RT mechanical properties. This scenario is ascribed to the impurity SiO₂ on the surface of SiC nanoparticles, which accelerates the α → β transformation and results in the weak bond between sialon grains and the increase of uncertainty of mechanical properties.