Évolutions microstructurales couplées de l'alliage d'aluminium 3003 au cours de traitements d'homogénéisation et influence d'un écrouissage préalable

Abstract : This work is dedicated to the structure evolutions associated with phase transformations at solid state in the 3003 alloy with and without mechanical stresses. The phase transformations sequences are studied from the as-cast state and up to the homogenization temperature thanks to several in situ experimental techniques (electrical resistivity, DSC, thermal diffusivity, TEM and synchrotron radiation). These analysis have allowed to precise the mechanisms, temperatures and kinetics of phase transformations, the morphologies and volume fraction of precipitated phases and their crystallography (unit cell parameter, orientation relationship.. .). The transformation of primary precipitates AI6(Mn,Fe) into [alpha]-AI(Mn,Fe)Si phase and the intragranular precipitation of dispersoïds are observed on heating from the as-cast state. The quantitative values obtained versus time and temperature in isothermal and anisothermal conditions have allowed to validate the results obtained by synchrotron radiation and with the precipitation model developed in the laboratory. We have also showed by EDX analysis coupled with TEM that the chemical composition of the phases varies with time and temperature and tend towards the equilibrium composition given by ThermoCalc. Using a similar approach, we have revealed the decrease of the transformation temperatures associated with strain hardening and the preferential precipitation of dispersoïds on the walls of the ce Ils provided by the deformation. The incidence of the dislocation density on the morphology of the precipitates and on the rate and kinetics of precipitation has also been quantified. The cell growing and the evolution of the dislocation density during the anisothermal treatment are also qualitatively analysed.
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Moukrane Dehmas. Évolutions microstructurales couplées de l'alliage d'aluminium 3003 au cours de traitements d'homogénéisation et influence d'un écrouissage préalable. Autre [cond-mat.other]. Institut National Polytechnique de Lorraine, 2004. Français. ⟨NNT : 2004INPL052N⟩. ⟨tel-01750018⟩

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