Caractérisation et prévision des structures en bandes dans les aciers Dual-Phase : lien avec les propriétés d'endommagement

Abstract : Modern cars are composed in weight of more than 50% of Dual-Phase steels. They combine a very good formability and high level of strength. This excellent mechanical accommodation is due to their two-phase microstructure, composed of hard martensite phase in a ductile ferrite matrix. These steels contain principally carbon and manganese. Chemical segregations developed during the casting create, after subsequent thermo-mechanical treatment, banded structures of ferrite and martensite unfavorable for damaging properties. Main objectives of this thesis were to understand mechanism of bands formation, and link their characteristic (intensity, topology?) to the process parameters. Some heat treatment routes derived of the industrial process were realized on sample of representative grade (Fe-0.15%C-1.5%Mn). Several experimental techniques (dilatometry, microscopy, electronic probe, EBSD?) were operating to understand mechanism of microstructures development. Some tool of visualization and quantification of the two-dimensional and three-dimensional were developed, enable to evaluate the influence of heat treatment parameters on the final microstructure. For different topologies, the local stress fields liable of damaging were estimated with the support of finite elements simulations. The collected information will allow loading numerical modeling with the purpose to reproduce microstructures genesis and to predict their mechanical behavior in high strain
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Benoit Krebs. Caractérisation et prévision des structures en bandes dans les aciers Dual-Phase : lien avec les propriétés d'endommagement. Autre. Université Paul Verlaine - Metz, 2009. Français. ⟨NNT : 2009METZ053S⟩. ⟨tel-01752922⟩

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