Transient Creep Associated with Grain Boundary Sliding in Fine-Grained Single-Phase Al2O3

Transient creep data for high-purity polycrystalline alumina are examined at the testing temperature of 1150–1250 °C. The data are analysed in terms of the effect of stress and temperature on the extent of transient time and strain.In order to explain the observed transient creep, a time function of creep strain is proposed from a two-dimensional model based on grain boundary sliding. The grain boundary sliding is assumed to take place by the glide of grain boundary dislocations accommodated by dislocation climb in the neighboring grain boundaries. The time function for a creep strain obtained from the model is given in a form which is similar to the previous empirical formula describing the experimental creep curves in metallic alloys. The model predicts that the transient creep strain T is approximately proportional to and the extent of transient creep time tT is inversely proportional to flow stress. The prediction is consistent with the experimental data in high-purity, fine-grained alumina at temperatures between 1150 and 1250°C.