Effect of Chemical Composition of Intergranular Glass on Superplastic Deformation of β-Silicon Nitride

Abstract

In this study, the effect of composition of intergranular glass on superplastic compressive deformation of -Si3N4 has been studied by compression tests. Oxide additives were used to form Y2O3-Al2O3-SiO2 melt and, with increasing temperatures, an oxynitride melt (Y-Al-Si-O-N) by dissolving Si3N4. The relation between flow stress and glass composition qualitatively corresponded to the effect of chemical composition on viscosity of Y2O3-Al2O3-SiO2 glass. However, the rate of increase of the flow stress was not proportional to the viscosity of Y2O3-Al2O3-SiO2 glass, probably because the composition of intergranular glass phase had changed by dissolving Si3N4 and by crystallization of Si2N2O.