The reaction hot-pressing of compositions in the system Al-Si-N-O corresponding to ??-sialon

Abstract

The reaction hot-pressing at 1700 and 1750° C of a number of compositions in the system Al-Si-N-O corresponding to points spanning theβ′-sialon phase line in the region of z=0.8 has been studied. Measurements have been made of densification rate and of the rate of conversion ofα-Si3N4 toβ′-sialon. The densification process for these compositions may be described in terms of a liquid-phase assisted fast particle rearrangement process succeeded by Coble creep. The rates of these processes are sensitive to the volume of grain-boundary liquid phase present, which in turn is determined by the position of the compositional point in relation to theβ′-sialon line. For systems containing very little grain-boundary phase, the vapour-phase transport of material may become important.