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Viscous Flow Creep in Ceramics Containing Secondary Crystalline Phases



Q Jin, D S. Wilkinson, G C. Weatherly, William E. Luecke, Sheldon M. Wiederhorn


Experimental observations of the creep response of a Y203-fluxed Si3N4 containing secondary crystalline phases(SP)are presented.The widths of grain-boundary amorphous films before and after creep have been characterized by using transmission electron microscopy.The results suggest that viscous flow of the boundary amorphous phase occurs during creep deformation.To better understand the experimental observations, a theoretical model is developed for viscous flow in ceramics containing SP grains. Previous models for viscous flow in glass-containing ceramics assume that the widths of intergranular films have a constant value throughout the material.In ceramics containing SP grains, however, two types of boundaries are formed, i.e.,heterophase and homophase boundaries.Usually, the film widths of hetero-phase boundaries are larger than that of homo-phase boundaries.This may give rise to different creep behaviour and local stress distribution.We have investigated the effect of SP grains on creep deformation due to viscous flow.A newtonian grain-boundary phase is assumed and a bimodal boundary-film thickness distribution is used to model the viscous flow process. A comparison is made between the experimental observations and predictions of this model.
Acta Materialia


creep, silicon nitride, viscous flow


Jin, Q. , Wilkinson, D. , Weatherly, G. , Luecke, W. and Wiederhorn, S. (2021), Viscous Flow Creep in Ceramics Containing Secondary Crystalline Phases, Acta Materialia (Accessed April 14, 2024)
Created October 12, 2021