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International audience; The mechanical characterisation of ultrathin specimens at very high temperature is challenging in terms of specimen preparation and mechanical testing under 'inert' atmospheres. An experimental procedure for the local characterisation of mechanical and thermal properties at elevated temperature is presented. Various common 'inert' atmospheres were investigated up to 1373 K in order to identify the most efficient environmental conditions to prevent surface reactivity and degradation of specimens. A NiCoCrAlYTa-coated monocrystalline Ni-based superalloy was used to exemplify the capabilities of the technique because of its high surface reactivity at very high temperature, i.e. oxidation and sublimation. Purified overpressured argon atmosphere combined with oxygen getters was found to be particularly suitable for the study of alumina-forming alloys at elevated temperature.

Cladding tubes are structural parts of nuclear plants, submitted to complex thermomechanical loadings. Thus, it is necessary to know and predict their behaviour to preserve their integrity and to enhance their lifetime. Therefore, a new experimental device has been developed to control the load path under multi-axial load conditions. The apparatus is designed to determine the thermomechanical behaviour of zirconium alloys used for cladding tubes. First results are presented. Creep tests with different biaxial loadings were performed. Results are analysed in terms of thermal expansion and of creep strain. The anisotropy of the material is revealed and iso-creep strain curves are given.

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