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modélisation de la recristallisation lors du forgeage à chaud de l’acier 304L – une approche semi-topologique pour les modèles en champs moyens

Abstract : Cooling system of nuclear power plants is constituted of metallic parts obtained by hot forging. Thus during the manufacturing process, the microstructural trans- formations induced by the deformation and annealing process define partially the mechanical properties of the final products. A sharp knowledge of the physical mechanisms generated within the material is required to handle the microstructure. In the case of hot deformation of 304L austenitic stainless steel, the microstructural modifications depend on the discontinuous dynamic recrystallization (DDRX) and the post-dynamic recrystallization (PDRX). The aim of this project is: (i) the study of the DDRX and the PDRX under the conditions of deformation inherent in the forging process, (ii) the study of the influence of niobium addition on these mechanisms, (iii) the modeling of these me- chanisms in order to predict the microstructure characteristics (mean grain size and distribution) following a multipass process. As part of the research, the deformation conditions experienced during the hot forging process are replicated through torsion tests with model materials containing various niobium concentrations. Characterization and modeling of microstructures enable to understand the respective e ects of temperature, strain rate as well as niobium addittion on the DDRX and PDRX mechanisms. In this study, a new topological approach of mean-field hypothesis is developed in order to allow the prediction of realistic grain size distributions.
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Submitted on : Friday, December 15, 2017 - 3:40:42 PM
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Guillaume Smagghe. modélisation de la recristallisation lors du forgeage à chaud de l’acier 304L – une approche semi-topologique pour les modèles en champs moyens. Autre. Université de Lyon, 2017. Français. ⟨NNT : 2017LYSEM003⟩. ⟨tel-01665156⟩

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