Effects of Composition on the Morphology of α-Sialon Ceramics

摘要

Elongated α-sialon (α′) grains were formed in Ca sialon materials through pressureless sintering. The development of elongated α′ grains strongly depends on the composition (i. e. the m-value in the α′ formula). The strong tendency for Ca α′ grains to grow into an elongated morphology may be attributed to a low viscosity transient liquid, which becomes more pronounced at high m-values. A lower eutectic temperature in the Ca sialon system, comparing to Y and rare earth sialons, may facilitate the development of the elongated α′. Elongated α′ grains with relatively high m-values could be readily formed by reducing the number of initially nucleated α′ grains at relatively low temperatures and promoting the growth of the α′ grains at high temperatures through rapidly heating the samples to the optimum grain growth temperature (1700-1800℃) for a long duration (4 hours).