Microstructural development of Y-α/(β)-sialons after post heat-treatment and its effect on mechanical properties

Dense Y-α and duplex Y-α/β-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 1300–1700 °C to investigate the thermal stability of Y-sialons. The results show that α-sialon stabilized by yttrium has high thermal stability. An adjustment of α-sialon phase composition is the dominating reaction during annealing. Post heat-treatment has a little effect on the microstructure and properties of the Y-α/β-sialons, but significantly changes the morphology of α-phase grains in Y-α-sialons from elongated to equiaxed after heat-treatment at 1500 °C for extended time, hence decreasing its toughness.