MECHANOCHEMICAL APPROACH TO THE OXIDATION OF ZIRCALOY-4

The deflection resulting from oxidation on one side of zircaloy-4 samples, at temperatures between 400 and 500-degrees-C, was followed by means of an optoelectronic device connected to an oxidation reactor. The stress evolution in the sample during the oxidation process was modelled via the different constituent relationships, accounting for the elastic response of the sample and its plastic behaviour. According to these, the zirconia films formed during the oxidation should reach their yield point rapidly after a short elastic response, while the metal substrate remains elastic. These experimental and theoretical studies of the combined chemical and mechanical phenomena involved during the oxidation of zircaloy-4 should contribute to a better understanding of both the service life and failure of this material. Despite its use so far only with one-dimensional geometry, the present model can serve as a basis for further additions and refinements. The good quantitative agreement which was achieved with the experimental data demonstrated that simple engineering models can be useful tools for giving general insight into mechanicochemical problems.