Un nouveau modèle de transformation de texture avec sélection des variantes : application à la transformation martensitique

Abstract : In the phase transformation of the solid state (especially the martensitic ones), the crystallographic texture of the final phase depends on the texture of the initail phase. However, the orientation relations (variants), which are observed in the transformation of the monocrystal, are in general not sufficient to predict the texture of the final phase from the texture of the initial phase. Indeed, many factors such as internal stresses, which are present before the transformation (or caused by the latter), can work towards a selection of variants. In this work we propose a model of texture transformation, which takes into account the selection of variants, by introoducing a variant selection function which describes, the effect of the "physical fields" on the transformation from the crystallographic point of view. This analytic expression, which is represented by a convolution integral, makes it possible, under certain conditions, to determine the variant selection function from the functions of the textures of the initial and final phases. So we obtained the variant selection functions from the functions of the texture of Fe3ONi sheets rolled in different conditions. This way of using the midel of transformation enables us to establish a "catalog" of variant selection functions which are associated to physical fields and this should make it possible to distinguish, by comparison, the main parameters, which rule the transformation. However, the most direct apllication of this transformation model is the prediction of the texture of the martensitic phase, the texture of the austenitic phase and the variant selection function being known. This model of transformation has also been used to test physical assumptions on the martensitic transformation of samples of rolled Fe3ONi sheets with complex textures, which are described from the crystallographic point of view by variant selection functions. The differences between the simulated texture and the experimental one constitute a test of validity of the proposed assumption. Thus we showed that for a large part of the grain population, the formed variants were those, which ensure the minimal deformation in the sheet plane. Systematical studies of morphology and dilatometry should confirm this result
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Michel Humbert. Un nouveau modèle de transformation de texture avec sélection des variantes : application à la transformation martensitique. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 1987. Français. ⟨NNT : 1987METZ018S⟩. ⟨tel-01775742⟩

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