High Temperature Creep Strength of Si3N4-Y2Si2O7 Ceramics by Stress Relaxation Based on a New Interpretation Model

Abstract

A new interpretation model, instead of classical Kohlrausch-Williams-Watt (KWW) equation, was applied to interpret stress relaxation behavior of Si3N4-Y2Si2O7 ceramics. Results revealed that the new model could obtain reasonable relaxation plastic viscosity and viscoelastic viscosity under testing temperature range of 1300°C~1575°C. From the plotted curve of viscosity vs 1/RT, an activation energy change occurred around 1500°C was found for both plastic viscosity and viscoelastic viscosity curves. This change, which indicated the microstructure change, was in good agreement with the significant decrease of high temperature strength retention property.