Imagerie de dislocations par contraste de canalisation des électrons : théorie et expérience

Abstract : The Electron Channeling Contrast Imaging (ECCI) is a Scanning Electron Microscope (SEM) technique used to contrast and characterize crystalline defects, such as dislocations. These latter generate, in fact, different contrasts according to the orientation of the incident beam with respect to the crystalline planes {hkl}: bright or black/white on a dark background, black on bright background…Theoretical models, based on dynamical diffraction theory, were first developed to describe the contrasts produced by a perfect crystal. Then, they were extended to the case of an imperfect crystal. Nevertheless, such theoretical models do not propose any detailed calculation and any analytical expression. In this thesis, we develop an original theoretical approach for modelling BSE intensity profiles in a crystal containing dislocations parallel to the surface. In this sense, we propose modelling for different diffraction conditions. Secondly, in order to understand the mechanisms of the formation of dislocation ECC images, we confront our experimental results with the obtained theoretical profiles. Finally, we propose a new approach for understanding the deformation mechanisms of materials near interfaces. This methodology consists in characterizing the areas of interest by ECCI before and after introducing, locally, the plastic deformation by nanoindentation. Here, we focus on the case of a TiAl bases alloy.
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Hana Kriaa. Imagerie de dislocations par contraste de canalisation des électrons : théorie et expérience. Science des matériaux [cond-mat.mtrl-sci]. Université de Lorraine, 2018. Français. ⟨NNT : 2018LORR0336⟩. ⟨tel-02331953⟩

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