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Modélisation des évolutions microstructurales et étude de la lubrification par film solide lors du filage à chaud d'alliages de zirconium

Abstract : Using torsion tests (with strain rate jumps) and an experimental hot mini-extrusion apparatus, several samples zirconium alloy have been deformed: Zircaloy-4 (high alpha range) and Zr-1Nb (alpha + beta domain). The fragmentation of the microstructure and post-dynamic grain growth have been examined. The main difference between these two alloys is that Zr-1Nb does not show grain growth during a heat treatment within the alpha + beta domain after hot deformation. The recrystallization volume fraction has been measured on extruded samples with or without heat treatment. These rheological and microstructural data have been used to determine the parameters of a microstructural model including: a work-hardening model (Laaasraoui/Jonas [LAA 91]), a continuous dynamic recrystallization model (Gourdet/Montheillet [GOU 03]) and a grain growth model. This model leads to a good prediction of recrystallization volume fraction for Zircaloy-4 extrusion. However, the Zr-1Nb model cannot be validated because of the difficulty to observe deformed microstructures. Extrusion process is lubricated with a solid film. Trapping tests show that this lubricant is thermoviscoplastic. Friction along the container and several observations show the lubrification is not realized by a continuous film. Indeed, the heterogeneousness of deformation of these alloys causes a rupture of the lubricant film. Experiments and numerical simulations show that the radial gradient of axial displacement is affected by friction but also by stress softening of the alloys.
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Submitted on : Thursday, April 16, 2009 - 3:33:17 PM
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  • HAL Id : tel-00376031, version 1

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Benoît Gaudout. Modélisation des évolutions microstructurales et étude de la lubrification par film solide lors du filage à chaud d'alliages de zirconium. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 2009. Français. ⟨tel-00376031⟩

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