Microstructure and mechanical properties of Dy-α-sialon/ nano-size SiC composites

The composite of Dy-α-sialon/10 wt pet nano-size SiC particles has been prepared from precursor powders of Si₃N₄, AlN, Al₂O₃, Dy₂O₃ and nano-size β-SiC. The hardness, toughness and bending strength of the composite at ambient temperature are a little higher than those of Dy-α-sialon, while the bending strength is maintained up to 1000°C and about 2 times more than that of Dyα-sialon at the same temperature. The fracture surfaces show that the grain size of the composite is smaller than that of Dy-α-sialon, and both of them have predominately transgranular mode of fracture. It is believed that the decrease of the bending strength of Dy-α-sialon at elevated temperature is caused by the viscous flow of the grain boundary phase, while the addition of nano-size SiC particles effectively increases the viscosity of the grain boundary phase and therefore prevents the strength loss of Dy-α-sialon/nano-size SiC composites at elevated temperature.