Deformed substructures in fine-grained tetragonal zirconia

Transmission electron microscopy (TEM) has been employed to examine the def ormed microstructures of a high-purity tetragonal zirconia polycrystal cont aining 3 mol% yttria. The TEM observations reveal that piled-up and tangled dislocations are developed within grains at a high stress, but such substr uctures do not appear at a lower stress, except for a small number of isola ted dislocations. The stress-dependent deformed microstructures suggest tha t the dislocation substructures observed at a high stress are not due to an y experimental artefacts. Applying a model proposed by Eshelby et al. to th e observed pile-up dislocations, it can be estimated that a stress concentr ation of the order of 14-25 is generated around multiple-grain junctions du ring deformation.