MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF DY-ALPHA-SIALON NANO-SIZESIC COMPOSITES/

The composite of Dy-alpha-sialon/10 wt pet nano-size SiC particles has been prepared from precursor powders of Si3N4, AlN, Al2O3, Dy2O3 and nano-size beta-SiC. The hardness, toughness and bending strength of th e composite at ambient temperature are a little higher than those of D y-alpha-sialon, while the bending strength is maintained up to 1000 de grees C and about 2 times more than that of Dy-alpha-sialon at the sam e temperature. The fracture surfaces show that the grain size of the c omposite is smaller than that of Dy-alpha-sialon, and both of them hav e predominately transgranular mode of fracture. It is believed that th e decrease of the bending strength of Dy-alpha-sialon at elevated temp erature is caused by the viscous flow of the grain boundary phase, whi le the addition of nano-size SiC particles effectively increases the v iscosity of the grain boundary phase and therefore prevents the streng th loss of Dy-alpha-sialon/nano-size SiC composites at elevated temper ature.