Grain boundaries characteristic temperatures

It is noted, however, that both of the above CaF2 and Ti02 nanoceramics had some amount of porosity. This may account for an apparent soft behavior related to the superplastic deformation at low temperature, which does not yet reveal the plastic deformation characteristics in nanoceramics. Localized superplastic deformation under cyclic tensile fatigue tests was observed by Yan et al. on 3Y-TZP nanoceramics at room temperature [25], The micromechanism behind this phenomenon is argued to be essentially governed by grain-boundary diffusion. The contribution of dislocation slip might be in operation as a parallel mechanism to develop slip band-like microfeatures. 

FIGURE 9.18. Coaise WC powder obtained by high-temperature carburization of a 25-pm tungsten powder. The smooth surface of the particles is characteristic for the high-temperature treatment (1900 °C) nevertheless, grain boundaries are still visible which indicates fliat the particles ate polyciystalline. By courtesy of Wolfimn Bergbau und Huttenges.m.b.H., Austria. 

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