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Analyse du comportement mécanique des constituants d'un alliage polycristallin multiphasé par diffraction des rayons X et neutronique

Abstract : The aim of this work is to propose a methodology using diffraction methods and theoretical approaches of self-consitent modeling in order to analyze and better understand the mechanical behavior of each phase of hot-rolled duplex stainless steel. The purpose of the experimental study is to characterize the local mechanical behavior of phases under uniaxial loading. X-ray and neutron diffraction which enable to measure strains in each phase separately were used in this aim. Austenitic and ferritic phase stresses are determined by X-ray diffraction during tensile tests. Evolution of the elastic strains in each phase was measured by neutron diffraction using « time-of-flight » method during tensile and compression tests. Elastic contants were given using the self-consistent model for a purely elastic deformation.
To reproduce the mechanical behaviour of the studied material, self-consistent polycrystalline micromechanical model for elastoplastic deformation has been adapted and confronted to experimental results. Cristallographic texture and initial residual stresses were considered in this analysis. Critical shear stresses and hardening parameters of each phase of the studied duplex steel have been identified. Results of this study showed that the austenitic phase represents the softest and the most hardenable phase. Taking into account in calculations the initial residual stresses in the non deformed sample leads to the conclusion that the initial stresses modify considerably the values of phase's yield stresses. Good agreement has been noted comparing results obtained by XRD to those obtained by neutron diffraction. The problem of relaxation of normal stresses in the analysed layer by X-rays was analysed and discussed. Using XRD and self-consistent modelling, the effect of the chemical composition of the duplex stainless steel and the influence of ageing at 400°C for 1000h on the mechanical behaviour of austenitic and ferritic phases have been established.
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Contributor : Rim Dakhlaoui <>
Submitted on : Wednesday, April 11, 2007 - 10:53:55 AM
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Rim Dakhlaoui. Analyse du comportement mécanique des constituants d'un alliage polycristallin multiphasé par diffraction des rayons X et neutronique. Mécanique [physics.med-ph]. Arts et Métiers ParisTech, 2006. Français. ⟨NNT : 2006ENAM0044⟩. ⟨tel-00141001⟩

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