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Étude expérimentale et modélisation par champ de phase de la formation de [alpha] dans les alliages de titane [bêta]-métastable

Abstract : The present study is mainly about microstructures formation during phase changes in the near beta titanium alloy Ti-5553. Phase transformations were characterized on cooling from the beta phase field and on ageing after solutionizing in the beta (or alpha + beta) phase field and quenching. The influence of heat treatment parameters (cooling and heating rates, transformation temperatures) on phase transformation kinetics, precipitation sequences and transformation mechanisms was analysed using electrical resistivity measurements, in situ high energy X-Ray diffraction and microscopy (optical and electron). Cell parameters evolution of each phase and full width at half maximum variations of beta phase peaks have allowed to highlight the changes of the chemical composition and the stress state during phase transformation. Formation of metastable phases (alpha?, w) at temperatures lower than 500°C were characterized as well as their influence on final microstructures and therefore on mechanical properties. For better understanding the intragranular precipitation of the alpha phase, two models (Eshelby and phase field) were developed in order to predict morphological evolutions of the precipitates. These models take into account the anisotropic and heterogeneous behaviour for both phases. We have shown that the elastic strain energy generated by beta -> alpha phase transformation drives to a large extent the precipitate shape and orientation as well as their spatial arrangement. Calculation results are close to microstructural observations
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Submitted on : Thursday, March 29, 2018 - 12:11:36 PM
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  • HAL Id : tel-01749279, version 1


Amico Settefrati. Étude expérimentale et modélisation par champ de phase de la formation de [alpha] dans les alliages de titane [bêta]-métastable. Autre. Université de Lorraine, 2012. Français. ⟨NNT : 2012LORR0092⟩. ⟨tel-01749279⟩



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