Effets des interfaces cristallines sur les champs mécaniques en plasticité cristalline et conséquences sur le glissement dans des micro-piliers bi-cristallins

Abstract : In order to better understand the role of grain boundaries in polycrystals deformation, the study of the mechanical behavior of bicrystals becomes necessary. In this study, an innovative experimental approach based on the fabrication of bicrystalline micropillars is investigated with a micromechanical analysis of crystal plasticity behavior. The theoretical approach is based on the static Field Dislocation Mechanics (FDM) theory in which the dislocations stored in the grain boundary are described by a continuous distribution of interfacial dislocations. This model provides explicit analytical expressions of the stress and lattice rotation fields in the case of an infinite bicrystal with planar boundary. The contribution of the different incompatibility sources are emphasized due to elastic and plastic anisotropies related to the different crystal orientations. Finite element simulations were also performed to validate this approach in a zone close to the grain boundary and far from the micropillar free surfaces. The experimental results are based on compression tests conducted at room temperature on Ni bicrystalline micropillars. The micropillars are machined on a Focused Ion Beam (FIB). First, the study is focused on the prediction of the resolved shear stresses on the possible slip systems in the bicrystal using the continuum model. The crystal volume fraction and the grain boundary inclination angle effects were also taken into account in the analysis. The predictions of the continuum-based approach developed in this thesis are in full agreement with the experimentally identified active slip systems. Concerning the onset of plasticity and the associated slip systems in each crystal, the developed model is more relevant than the Schmid law. The compression tests are followed by microstructural EBSD measurements to quantify lattice rotations in each grain during the deformation which were also computed using the micromechanical model developed in the present thesis
Document type :
Theses
File URL :
http://docnum.univ-lorraine.fr/prive/DDOC_T_2015_0174_TIBA.pdf
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https://hal.univ-lorraine.fr/tel-01754468
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Submitted on : Friday, March 30, 2018 - 9:50:21 AM
Last modification on : Tuesday, May 28, 2019 - 3:40:14 PM

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  • HAL Id : tel-01754468, version 1

Citation

Idriss Tiba. Effets des interfaces cristallines sur les champs mécaniques en plasticité cristalline et conséquences sur le glissement dans des micro-piliers bi-cristallins. Autre. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0174⟩. ⟨tel-01754468⟩

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