The Measurement of Compressive Creep Deformation and Damage Mechanisms in a Single-Phase Alumina Part II Correlation of creep cavitation and grain boundary sliding

Abstract

It has been theorized that stochastic grain boundary sliding (GBS) is the primary driving force for the nucleation, growth, and coalescence of cavities located on the grain boundaries of polycrystalline ceramics undergoing creep. This paper reports on the results of co-ordinated measurements of both GBS and creep cavitation during the creep of a single-phase alumina. Constant compressive stress creep experiments were performed at a temperature of 1600 °C, and stress levels of 70, 100, and 140 MPa. Small angle neutron scattering measurements (SANS) show that cavities nucleate continuously due to creep at all three stress levels, and that since negligible cavity growth was measured, creep cavitation appears to be ruled by a nucleation rather than a growth process. Also, at a constant creep temperature, the number and volume of cavities measured was observed to decrease with a decrease in the applied stress. GBS displacements reported in Part 1 of this paper [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.