The effect of heat-treatment on the performance of sub-micron SiC_p-reinforced α-β sialon composites: II. Heat-treatment studies

The effects of heat-treatment on α → β sialon transformation in dense, agglomerate-free Ln-sialon/ SiC_p(Ln=Nd, Yb) composites are reported. The stability of the α-sialon phase is not only dependent on the temperature and time of heat-treatment, but also on the kind of additive and the amount of SiC particles. In Nd-densified samples, the a-sialon phase is very unstable at 1450°C and transforms almost totally to the β phase with the Nd-M (melilite) phase and NdAlO₃ as grain-boundary crystalline phases. In contrast, Yb³⁺-densified samples show good stability for the a-sialon phase at 1450°C, with only a small amount of β-sialon produced. The crystalline grain-boundary phases produced in this case are Yb-garnet, and Yb-J-phase.