Morphology of cavities measured by neutron scattering in superplastically deformed 3Y-TZP

Cavities are often formed and grown at grain boundaries in metals and ceramics during superplastic deformations and influence strongly their mechanical, physical and thermal properties. Therefore, it is necessary to accurately know the distribution of dimensions, shapes and quantities of the cavities in the superplastically deformed materials. In this study, a trial by using a small angle neutron scattering (SANS) method was performed to measure the distribution of dimensions and quantities of the cavities in 3mol% yttria stabilized tetragonal zirconia polycrystal (3Y-TZP) caused by superplastic deformations. Tensile test specimens of 3Y-TZP were pulled at 1723 K in the air to nominal strains from 0.0 to 200 %, and then furnace-cooled. The volume fraction of cavities increases with increasing the nominal strain. The measurements of cavities were also performed conventionally by the image processing on SEM micrographs and the bulk density measurement, and the results are compared with those obtained by the SANS method and discussed.