The measurement of compressive creep deformation and damage mechanisms in a single-phase alumina part II - Correlation of creep cavitation and grain boundary sliding

It has been theorized that stochastic grain boundary sliding (GBS) is the p rimary driving force for the nucleation., growth, and coalescence of caviti es located on the grain boundaries of polycrystalline ceramics undergoing c reep. This paper reports on the results of co-ordinated measurements of bot h GBS and creep cavitation during the creep of a single-phase alumina. Cons tant compressive stress creep experiments were performed at a temperature o f 1600 degrees C, and stress levels of 70, 100, and 140 MPa. Small angle ne utron scattering measurements (SANS) show that cavities nucleate continuous ly due to creep at all three stress levels, and that since negligible cavit y growth was measured, creep cavitation appears to be ruled by a nucleation rather than a growth process. Also, at a constant creep temperature, the n umber and volume of cavities measured was observed to decrease with a decre ase in the applied stress. GBS displacements reported in Part 1 of this pap er [1] are related to the number of cavities nucleated per unit volume and shown to relate directly, thereby providing experimental evidence that GBS may act as the driving force for creep cavitation. (C) 1998 Kluwer Academic Publishers.