Grain boundary sliding-induced deformation in a 30 wt% zirconia–spinel composite: influence of stress

Abstract

The contribution of grain boundary sliding to total strain has been investigated in a 21 vol% zirconia–spinel composite crept under stresses of 12 and 90 MPa. To this goal, the surface topography and its changes with strain were investigated on a face parallel to the compression axis by atomic force microscopy in contact mode. Due to the low zirconia content, only sliding on spinel–spinel (S–S) and spinel–zirconia (S–Z) boundaries really contributes to strain and was consequently analysed. Insensitive to stress value, boundary sliding can account for 70–80% of the total strain. However, if the two investigated interfaces behave similarly at 90 MPa, at 12 MPa sliding on S–Z boundaries is larger than on S–S ones. That difference is to relate to a stress–strain rate sensitivity dependent on stress, 1.8 and 4.2 at 90 and 12 MPa, respectively, an increase in the stress exponent able to be induced by the existence of a threshold stress that would concern spinel–spinel boundaries.