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Theses

Modélisation de l'influence de la structure des joints de grains sur les phénomènes de ségrégation.

Abstract : This thesis focuses on the modeling of grain boundaries (GB) structure and segregation phenomena. Segregation at GB in polycrystalline materials can have profound consequences on structural and functional properties : intergranular slipping, intergranular corrosion and mechanical properties. Segregation becomes really important in irradiated materials where radiation-induced segregation can change th local composition of GB and sometimes impact the macroscopic properties of materials. In this work, the quasi-particles approach is developed to model these phenomena in binary systems. The quasi-particles approach is a continuous model able to model physical phenomena at atomic scale. One of the insight of this model is the capability to simulate atomic displacement in continuum space and diffusive transitions at mesoscale. In this work, the quasi-particles approach is used to study phosphorus segregation at GB. The link between GB structure and phosphorus concentration is highlighted. Next, vacancies or self-interstitial are introduced into the quasi-particles approach to model some specific phenomena which occur in irradiated materials. In particular, the diffusion and annihilation of vacancies (or self-interstitials) at GB could be modeled. When sink strength of GB is large enough, vacancies diffuse to GB and create voids with elongated shape, consistantly with experimental observation. Finally, the quasi-particles approach is used to study grain growth in polycrystalline materials.
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Antoine Vaugeois. Modélisation de l'influence de la structure des joints de grains sur les phénomènes de ségrégation.. Matériaux. Normandie Université, 2017. Français. ⟨NNT : 2017NORMR096⟩. ⟨tel-01817017v2⟩

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