Etude morphologique et structurale des produits de décomposition de la ferrite delta dans un acier inoxydable austéno-ferritique Fe-22Cr-5Ni-3Mo-0.03C

Abstract : This investgation, using a Z3CND-22-05 duplex stainless steel, was carried out to provide more information on the morphological and structural features of the decomposition of delfa ferrite. Optical and electron (TEM and HREM) microscopies together with the electron diffraction (microdiffraction and CBED) coupled with the Energy Dispersive X-ray microanalysis are used to identify the precipitates and examine their chemical composition. The orientation relationships between the phases are determined. The precipitate morphology is discussed in terms of the symmetry elements and precipitation mechanisms are proposed. The isothermal decomposition of delta ferrite leads to austenite formation. At later stages of ageing, the austenite transforms to lath martensite. During continuous cooling, an austenite-M23C6 aggregate precipitates. In the temperature range between 650°C and 970°C, two major phases, sigma and khi, precipitate at the delta-gamma interface. The sigma phase adopts an unspecified form and appears as aggregates of sigma-ferrite and sigma-austenite. In the temperature range between 450°C and 650)C, four intragranularphases were identified ; the Frank and Kasper R-phase, a Cr-rich ferrite, an austenite with an arrow-type morphology and a novel orthorhombic phase which belongs to the Fmmm space group
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Theses
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http://docnum.univ-lorraine.fr/prive/INPL_T_1991_REDJAIMIA_A.pdf
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https://hal.univ-lorraine.fr/tel-01752172
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Submitted on : Thursday, March 29, 2018 - 1:33:38 PM
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Abdelkrim Redjaïmia. Etude morphologique et structurale des produits de décomposition de la ferrite delta dans un acier inoxydable austéno-ferritique Fe-22Cr-5Ni-3Mo-0.03C. Autre. Institut National Polytechnique de Lorraine, 1991. Français. ⟨NNT : 1991INPL020N⟩. ⟨tel-01752172⟩

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