Thèses sur le sujet « Caractérisation de la microstructure et la texture cristalline »
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Khabouchi, Amal. « Microstructure, texture et propagation des ondes ultrasonores dans un superalliage à base de nickel fait par fabrication additive ». Electronic Thesis or Diss., Université de Lorraine, 2021. https://docnum.univ-lorraine.fr/public/DDOC_T_2021_0349_KHABOUCHI.pdf.
Texte intégralAdditive Manufacturing is a revolutionary industrial technique that has attracted increasing interest since the late 1980s and is gradually beginning to replace conventional manufacturing processes, and even to open horizons for the creation of new types of materials. This importance is attributed to it thanks to several specificities, namely the almost infinite possibility of building parts with complex geometries and the possibility of mixing several types of powders with different chemical compositions to obtain materials with well-defined properties depending on the final applications. These materials are often referred to as functionally graded materials. Additive manufacturing is even used to build composite materials. It is now used in almost all industrial fields: aerospace, medical, automotive and electronic components. The extension of additive manufacturing to metal alloys is even more recent. Over the past 20 years, many metal additive manufacturing processes have been developed. Examples include laser powder bed fusion (called SLM or L-PBF), direct additive laser construction (CLAD), selective laser sintering (SLS), etc... Although that it is a very promising technique, additive manufacturing, especially the metallic one, is still poorly controlled. Considerable technological work has been done to optimise the manufacturing parameters and improve the properties, particularly mechanical ones, of the parts produced. However, to fully use the advantages of the technique, a major research effort remains to be made to fully understand and control the fine mechanisms involved in the processes. As a result, the scientific community is currently very active in this field and the publications are very numerous. From a metallurgical point of view, two points seem to be important for the mechanical strength of the parts. On one hand, the presence of porosities, in a greater or lesser proportion, in the deposited material, which can le ad to a decrease in its resistance. On the other hand, the crystalline texturing inherent in the process used, which results in an anisotropic mechanical behaviour. The work of this thesis is in this context. It was conducted as part of a collaboration between the LEM3 in Metz and CEA-LIST in Saclay, integrated within a wider program of research and innovation joining CEA-Tech Lorraine and the Region of Lorraine. The CEA-LIST is specialized -among other things- in the development of non-destructive control methods (NDT) to detect the presence of defects in metal parts. LEM3 has particular competence in quantifying and understanding the crystalline textures of metal alloys related to their elaboration conditions. From a scientific point of view, the objectives of the thesis were twofold: on the one hand, our objective was to improve our understanding of the genesis of crystalline textures during the deposit of a metal alloy by SLM; On the other hand, we aim to evaluate the consequenc es of these textures on the propagation of the ultrasound waves which are traditionally used in CND. From a more practical point of view, the question that arose at the beginning of the thesis was: does the elastic anisotropy of propagation of ultrasound linked to the crystalline texturing produced by the SLM process require a review of the protocol of non-destructive control by ultrasound?
Jouili, Mohamed. « Caractérisations Mécaniques et Microstructurales des Films de Zircone Obtenus Par MOCVD et Sol-Gel ». Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00684387.
Texte intégralLi, Li. « Caractérisation et identification du comportement thermomécanique de multi-cristaux d’aluminium ». Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20147/document.
Texte intégralThe main objective of this PhD thesis is to establish an energy balance at the grain scale in order to assess the thermomechanical consistency of material models used to predict the development of crystal plasticity of metals.The first part of this work consists in setting a protocol allowing the material elaboration with the desired microstructure which is to be compatible with the use of classical macroscopic observation devices. The obtained coarse-grained aluminum samples (with centimeter grains) are used in cyclic tensile tests. During these tests, the kinematic and thermal fields are recorded with Digital Image Correlation and Infra-Red Thermography techniques.Two specific imaging techniques were developed. They allow introducing ad hoc hypotheses (i.e. consistent with microstructure) on the kinematic and the thermal fields. In this work, these hypotheses consist in intra-granular continuity conditions on the displacement, temperature and heat flux fields. These methods give independent measures on each grain while improving the robustness of the measurement methods. These methods were numerically validated using computer-generated images heterogeneously loaded.Cyclic tests were finally performed on the processed aluminum multi-crystals. The developed methods allowed the observation of the development of intra-granular plasticity and the development of inter-granular cracking
Lim, Sze Mei. « Caractérisation et modélisation des microstructures et des textures d'alliages ferritiques en grande déformation : genèse d'alliages à grains ultrafins ». Saint-Etienne, EMSE, 2008. http://www.theses.fr/2008EMSE0035.
Texte intégralL’affinement de la microstructure par l’application de déformations intenses (>> 1) permet une amélioration de certaines propriétés mécaniques d’un matériau, notamment une augmentation de la limite d’élasticité à travers la loi de Hall et Petch, tout en évitant des ajouts importants d’éléments d’alliage. La maîtrise de la production d’aciers à grains ultrafins (1 à 2 μm) conduirait donc à des allègements de structures tout en assurant un recyclage aisé. Dans ce travail, l’affinement de la microstructure par torsion et par compression multiaxiale a été étudié dans deux alliages modèles, Fe-C et Fe-Nb. Des analyses par EBSD montrent que l’affinement a lieu par la fragmentation de la microstructure initiale impliquant des processus microstructuraux et texturaux associés à la recristallisation dynamique continue (RDC). Le meilleur affinement a lieu à une température intermédiaire qui se situe entre des températures qui correspondent à la déformation « à froid » et « à tiède » du matériau ; sa position exacte varie selon la composition chimique et elle est plus élevée dans le Fe-Nb que dans le Fe-C. La torsion s’avère plus efficace que la compression multiaxiale car elle permet de générer une plus grande proportion de parois de forte désorientation et une taille de microstructure plus fine pour la même déformation totale appliquée. Toutefois, le développement d’une texture composée majoritairement d’une seule orientation D2 (1 12)[111] au régime stationnaire en torsion (cisaillement négatif) va à l’encontre de l’affinement car cela entraîne la coalescence de sous-grains voisins qui sont les produits de la fragmentation aux premiers stades de la déformation. Un modèle de textures incorporant la croissance sélective des grains provoquée par des gradients de taux d’écrouissage entre grains d’orientations diverses montre que la formation de l’orientation D2 est fortement liée à la migration des joints de grains. L’addition d’une petite quantité (500 ppm massique) de niobium, qui est réputé pour freiner les joints de grains par un effet de traînage des solutés, permet de ralentir la formation d’une telle texture et donc d’assurer la persistance d’une taille de microstructure ultrafine
Meslin, Sophie. « Infiltration et croissance des céramiques YBa2Cu3O7-X texturées à structure perforée : relations microstructures et propriétés supraconductrices ». Caen, 2006. http://www.theses.fr/2006CAEN2022.
Texte intégralThe superconducting oxide YBa2Cu3O7 (Y123), with its critical temperature of 92 K woke up with its discovery a great enthusiasm and continues to be the source of many works. Thanks to its good superconductive properties at the liquid nitrogen temperature (77 K) it seems to be very promising for the applications under magnetic field. In order to obtain higher critical current densities, it is necessary to increase their bulk density and to induce a preferential crystallographic orientation. This work consisted of elaborating improved samples in term of superconducting properties. The conventional texture process induces cracks and porosities in the samples and requires addition of doping agents in order to improve materials properties. We have studied a new process named "infiltration and growth" as well as an original geometry "with thin walls". The characterizations carried out on this superconducting microstructures, concerning texture and properties are reported. The optimization of the synthesis process consisted in understanding the mechanisms of infiltration and growth, then to seek the configuration and the composition giving of the most powerful samples. Critical currents densities close to 68 kA/cm2 under self field have been measured at 77 K. The study of the perforated samples showed that, thanks to the artificial "holes", the microstructures are free of porosities and the samples cool more quickly. Concerning the oxygenation process of the samples this take place easier and its more homogeneous, compared to non-perforated pellets
Delorme, Fabian. « Influence de la microstructure et de la texture sur les propriétés supraconductrices de céramiques (RE,Y)Ba2Cu3O7-d texturées. Synthèse et caractérisation ». Phd thesis, Université de Caen, 2002. http://tel.archives-ouvertes.fr/tel-00444049.
Texte intégralDelorme, Fabian. « Influence de la microstructure et de la texture sur les propriétés supraconductrices de céramiques (RE,Y)Ba2Cu3O7-delta texturées : Synthèse et caractérisation ». Caen, 2002. http://www.theses.fr/2002CAEN2012.
Texte intégralChen, Zhe. « Relation microstructure et propriété mécanique des films de ZrO2 obtenus par MOCVD ». Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00637177.
Texte intégralGiovannelli, Fabien. « Synthèse, texturation et caractérisation de céramiques supraconductrices (TR)Ba2Cu3Oy (TR = Nd, Sm, Eu, Gd) ». Caen, 2002. http://www.theses.fr/2002CAEN2027.
Texte intégralBaroghel-Bouny, Véronique. « Caractérisation microstructurale et hydrique des pâtes de ciment et des bétons ordinaires et à très hautes performances ». Phd thesis, Ecole Nationale des Ponts et Chaussées, 1994. http://tel.archives-ouvertes.fr/tel-00523299.
Texte intégralBarrat, Sylvère. « Caractérisations morphologiques, chimiques, et structurales de cristaux et films de diamant élaborés par un procédé de dépôt chimique en phase vapeur assisté par plasma micro-onde ». Vandoeuvre-les-Nancy, INPL, 1994. http://docnum.univ-lorraine.fr/public/INPL_T_1994_BARRAT_S.pdf.
Texte intégralRakotoarison, Sylvain. « Effets du champ magnétique sur la solidification d'alliages : texturation, blocage de la convection de Marangoni et séparation par force magnétique ». Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10205.
Texte intégralBlaise, Arnaud. « Caractérisation microstructurale d'un PEHD semi-cristallin déformé, par tomographie X et diffusion de lumière polarisée ». Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10023/document.
Texte intégralThis thesis mainly concerns the characterization of High Density Polyethylene (HDPE) at the microscopic scale when mechanically solicited. A first part presents a modeling strategy of the polymer behavior that is representative of the observations at the macroscopic scale and adapted to a good metrology of its constitutive parameters. Then, this work focus on investigation techniques that probe the mesoscopic scale (micrometer scale) through a technique (in-situ) based on the transport of incoherent and polarized light (IPSLT) ; and synchrotron X-ray microtomography. The aim is to understand the phenomena that take place at this scale during the successive phases of matter transformation (which switch from a homogeneous biphasic quasi-isotropic state to a very anisotropic fibrillar mesostructure). We show that this polymer does not exhibit any cavitation phenomena and that contrary to most of the results published in the literature, whitening which can be observed macroscopically is not due to the presence of cavities. This result suggests that the mechanical deformation processes put at stake in elastoviscoplasticity with hyperelastic hardening can take place without paramount porosity mechanisms and paves the way for new scenarios that could explain the microstructure evolution as function of strain
Chovet, Sauvage Corinne. « Evolution des microstructures et des textures en grande déformation à chaud d'un alliage Al-Mg-Si : caractérisation du mécanisme de recristallisation dynamique continue ». Grenoble INPG, 2000. http://www.theses.fr/2000INPG4210.
Texte intégralLi, Jia. « Simulation par éléments finis de la propagation de fissures de fatigue dans les matériaux polycristallins imagés par tomographie aux rayons X ». Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0079/document.
Texte intégralThe short fatigue crack propagation in polycrystal materials depends strongly on microstructure. Although numerous studies of characterisation and of simulation, the prediction of the short fatigue crack propagation remains a challenge.In order to understand the mechanisms of short fatigue crack propagation, an in-situ characterisation by X-ray tomography was carried out at ESRF, using two techniques of tomography. Diffraction Contrast Tomography (DCT) that is a non-destructive method can be used to obtain 3D morphology and grain orientations in an undeformed state of polycrystal materials. Couple with Phase Contrast Tomography (PCT), it allows to characterise the short fatigue crack propagation at different loading stages. Access to this information, it is possible to simulate the short fatigue crack propagation using a 3D reel microstructural mesh reconstructed from the tomographic images.In this work, the elastic anisotropic behaviour in a 3D microstructural mesh is performed. The elastic strain tensors averaged in grains are also compared to the experimental measurements. Then, a new numerical approach is proposed to simulate crack propagation. From a crystal plasticity FE simulation, the crack growth direction is determined by a post processing. Next, the crack is propagated through remeshing. This approach is firstly applied to the single crystals, then to the polycrystal mesh reconstructed from the tomographic images. The grain boundary effects and the crack growth rate are also analysed. By comparing between simulation and experimental crack, the damage indicator is discussed at the end