Abstract
Effects of SiC particle dispersions with average particle size in the range of 0.04-125μm on the α-β phase transformation and room temperature mechanical properties were investigated for Si3N4/SiC composites containing a 30vol% SiC particle. All composites were fabricated by hot pressing the mixture of sub-micron sized α-Si3N4 and α or β-SiC powders using 8wt% Y2O3 as a sintering additive. Addition of finest SiC particle (40nm) affected considerably the α-β phase transformation of Si3N4 matrix and the microstructure was composed mostly of fine equiaxed grains. As increasing the size of added SiC particles, the α-β phase transformation and the grain growth of β-Si3N4 were found to be promoted up to 25μm SiC and then saturated. As decreasing the size of added SiC particles, the fracture strength was increased and then saturated. The addition of finest SiC particle, however, was found to decrease the fracture strength drastically. The fracture toughness was increased as increasing the size of added SiC particles.
