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Influence de la microstruture sur le glissement intergranulaire lors du fluage d'un superalliage pour disques

Abstract : The aim of this study is to highlight the influence of initial microstructure on grain boundary sliding during high-temperature creep of a polycrystalline nickel-based superalloy. To reach this goal, several microstructures are produced from the reference microstructure of NR6 alloy by adequate heat treatments. The influence of microstructural parameters on local deformations is then studied thanks to a microextensometry technique coupled with an electron back-scattered diffraction analysis. It thereby enables linking microstructure, local deformations and macroscopic creep behaviour. In the case of NR6 alloy reference microstructure, deformation occurs mainly by γ and γ' phases cutting by dislocations. This mechanism is grain boundary sliding-favourable. The absence of tertiary γ' phase precipitates promotes secondary precipitates bypassing by dislocations. This results in a reduction of grain boundary sliding but is also harmful to the alloy creep resistance. Grain boundary serration improves grain boundary sliding resistance but diminishes intragranular deformation resistance by favouring precipitate bypassing. Then global deformation resistance is not changed. Finally, grain size increase has influence neither on activated deformation mechanisms nor on sliding amplitude. However, the decrease of grain boundary fraction leads to a reduction of grain boundary sliding contribution to overall strain.
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Submitted on : Thursday, July 18, 2013 - 11:40:10 AM
Last modification on : Friday, March 25, 2022 - 9:41:37 AM
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  • HAL Id : tel-00845938, version 1



Kevin Thibault. Influence de la microstruture sur le glissement intergranulaire lors du fluage d'un superalliage pour disques. Autre. Université de Grenoble, 2012. Français. ⟨NNT : 2012GRENI038⟩. ⟨tel-00845938⟩



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