Étude expérimentale et prévisions par le calcul des cinétiques de transformation de phases, des contraintes résiduelles et des déformations lors de la transformation bainitique

Abstract : A fully bainitic microstructure is required for some mechanical steel parts. The simulation of the dedicated heat treatment process is necessary to optimise the parts in terms of final microstructures (i.e. mechanical properties), residual stresses and distortions. The first part of the work deals with the experimental study of the bainitic transformation kinetics, the thermomechanical behaviour of the formed microstructures and the effect of an applied stress on the bainitic transformation (transformation plasticity and kinetic effect) for a middle alloyed steel. Different models for the prediction of phase transformation kinetics and thermomechanical behaviour (macroscopic and microscopic cnes) have been used at the scale of specimen without gradients. The .experimental validations at that scale have allowed to move to the scale of massive specimen (with high gradients) for whlch the dlfferent coupllngs between thermal, metallurglcal and mechanlcal phenomena have been taken into account in finite element simulations. The influence of phase transformations on the development of internai stresses and deformations during cooling have been analysed in details. Moreover, quenching experiments with in-situ temperature measurements have allowed to validate the numerical simulations. It has been pointed out that it is necessary to take into account the effect of internai stresses on bainitic transformation kinetics to predict final microstructure and hardness distributions.
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Theses
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http://docnum.univ-lorraine.fr/prive/INPL_T_2003_VEAUX_M.pdf
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Submitted on : Thursday, March 29, 2018 - 12:40:15 PM
Last modification on : Monday, April 16, 2018 - 10:41:04 AM

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Michaël Veaux. Étude expérimentale et prévisions par le calcul des cinétiques de transformation de phases, des contraintes résiduelles et des déformations lors de la transformation bainitique. Autre [cond-mat.other]. Institut National Polytechnique de Lorraine, 2003. Français. ⟨NNT : 2003INPL050N⟩. ⟨tel-01750189⟩

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