Abstract

Dense Y-alpha and duplex Y-alpha/beta-sialon ceramics were fabricated by hot isostatic pressing (HIP) using the compositions with the formula Ym/3Si12-(m+n)Alm+nOnN16-n, and extra addition of 2 wt-%Y2O3. The sintered materials were subsequently heat-treated at 1300-1700degreesC to investigate the thermal stability of Y-sialons. The results show that alpha-sialon stabilized by yttrium has high thermal stability. An adjustment of alpha-sialon phase composition is the dominating reaction during annealing. Post heat-treatment has a little effect on the microstructure and properties of the Y-alpha/beta-sialons, but significantly changes the morphology of alpha-phase grains in Y-alpha-sialons from elongated to equiaxed after heat-treatment at 1500degreesC for extended time, hence decreasing its toughness.