On the Accuracy of Elastic Strain Field Measurements by Laue Microdiffraction and High-Resolution EBSD: a Cross-Validation Experiment

Determining the accuracy of elastic strain measurements in plastically deformed alloys is an experimental challenge. To develop a novel cross-validation procedure, a controlled elasto-plastic strain gradient was created in a stainless steel single crystal by four point bending deformation. The corresponding elastic strain field was probed, with an intragranular spatial resolution, in-situ by Laue microdiffraction and ex-situ by High Resolution EBSD. Good agreement is found for the two independent measurements and the predictions of a mechanical model, at plastic strains below 0.5 %. The accuracy of the measurements is estimated at 3.2 × 10 − 4

Couplage fluage-recristallisation dans les alliages de zirconium

L'objectif de cette thèse est de comprendre et de modéliser le comportement du Zircaloy-4 au cours du transport du combustible usé. Nous avons développé un modèle couplant la recristallisation, la restauration et le comportement mécanique. L'utilisation de la microscopie électronique a validé les observations préexistantes sur la recristallisation statique et a montré que l'application d'une contrainte influence la germination et la croissance des nouveaux grains. Le premier effet est décrit physiquement en ajoutant un terme de friction au modèle de recristallisation et le second est implicitement inclus dans le modèle couplé. Le fluage est modélisé par un modèle polycristallin pour prendre en compte l'effet de l'anisotropie de comportement du zirconium et les hétérogénéités de la microstructure. Le comportement local est décrit par un modèle à bases physiques ajoutant un potentiel prédictif au modèle antérieur.The thesis aim is to understand and to model the behavior of Zircaloy-4 during the transport of spent fuel. We developed a model coupling the recrystallisation, the recovery and the mechanical behavior. Electron microscopy confirmed the pre-existent observations on static recrystallisation and showed that the application of a stress influences both the nucleation and the growing of new grain during recrystallisation. The former effect is physically described by adding a term of friction to the recrystallisation model and the latter implicitly included in the coupled modeI. The creep is modelled by a polycristallin mode] to take into account the etTect of the anisotropic behavior of zirconium and microstructure heterogeneity. The local behavior is described by a physically based model which adds a predictive potential to the previous model.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF