Effect of MoSi2 Particles on the Fracture Toughness of AlN-, SiC-, and Si3N4-based Ceramics

The effect of 30 vol% MoSi2 addition on the fracture toughness of AlN-, SiC-, and Si3N4-based composites is investigated. To isolate the contribution of MoSi2 particulate, the toughness of the composite is compared to that of the reference AlN, SiC, and Si 3N4 matrixes. It turns out that the main toughening mechanisms are residual stress and crack deflection. The residual stress is evaluated through the strain measure in the reinforcing particles by X-ray diffraction, and the crack deflection by analysis of the crack paths. The overall toughening effect is calculated as the sum of these two contributions compared to the experimental values of the toughness of the composites.