Characterization of Grain Boundaries in Superplastically Deformed Y-TZP Ceramics

The effects of compressive deformation on the grain boundary characteristics of fine-grained Y-TZP have been investigated using surface spectroscopy, impedance analysis, and transmission electron microscopy. After sintering at low temperature (1150°C), the grain boundaries are covered by an ultrathin (1nm) yttrium-rich amorphous film. After deformation at 1200°–1300°C under low stress, some grain boundaries are no longer covered by the amorphous film. Yttrium segregation seems to occur only at wetted grain boundaries. Evidence has been found that the extent of dewetting increases with increasing applied stress

Low-Temperature Sinter Forging of Nanostructured Y-TZP and YCe-TZP

Compacts of ultrafine Y-TZP and YCe-TZP powders have been sinter forged under constant load at low temperatures (1100°–1200°C). The application of a uniaxial load leads to a strong reduction in sintering time, which in combination with the virtual absence of dynamic grain growth makes it possible to effectively limit grain growth. Nanostructured (grain size 100 nm) TZP with high relative densities (90%-93%) could thus be produced by sinter forging under 84 MPa at 1100°C. The contributions of both creep and densification to the dimensional changes of the sinter-forging samples have been analyzed. A strong reduction of the flaw concentration was observed in sinter-forged materials as compared to freely sintered ones