Dissertations / Theses on the topic 'Microstructure (physique) – Microscopie'
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Mamoun, Abdeslem. "Etude par microscopie électronique en transmission de la microstructure de fluage d'alumines polycristallines." Lyon, INSA, 1994. http://www.theses.fr/1994ISAL0059.
The complete comprehension of mechanical damage mechanisms, particularily by creep, of thermomechanical ceramics requires obviously a thorough microstructural characterization of these materials. The present work is devoted to a microstructural study of two polycrystalline ceramics by Transmission Electron Microscopy (TEM). The first of these two materials is a fine-grained polycrystalline alpha-alumina. It has a good creep behaviour (i. E. , a low creep rate). TEM study after deformation reveals a cavitation process, which has been evaluated by a statistical approach (i. E. , cavity counting). Results of mechanical tests, previously obtained on this material, have been re-interpreted in terms of theoretical creep models available in the literature; the "interface-controlled diffusional creep" mechanism (in agreement with TEM observations) leads to consistent values for the main parameters of the creep law (i. E. , creep rate and creep exponent). The second material is a similar alpha-alumina, but containing non-negligible quantities of impurities (magnesium and potassium oxides). These compounds lead to the presence of a minor crystalline second-phase, i. E. Potassium beta"' alumina, which has been characterized by means of Conventional, Analytical and High-Resolution Transmission Electron Microscopy in the as-received material. This second phase has a spectacular structural evolution in creep: firstly, the beta"' particles convert into spinel phase; the associated volume decrease promotes mechanical damages (nucleation of cavities and microcracks near beta-alumina based particles). Secondly, the diffusion of potassium ions out of platelets during this transformation induces a chemical attack of surrounding alpha-alumina grains. This process has been extensively studied by TEM, and analyzed consistently from a thermodynamical point of view (evaluation of standard Gibbs energy changes of corrosion reactions, and proposition of a realistic scenario explaining the successive physico chemical reactions occurring during creep, and also, during the preparation of thin foils). All these experimental results demonstrate the benefits of TEM for the study of mechanical properties of ceramics
Pechard-Presson, Béatrice. "Méthodologie pour l'étude par analyse d'images de la microstructure de matériaux composites biphasés." Vandoeuvre-les-Nancy, INPL, 1997. http://docnum.univ-lorraine.fr/public/INPL_T_1997_PECHARD_PRESSON_B.pdf.
Reinier, Eric. "Etude de la microscrostructure et des défauts dans les quasicristaux réels." Aix-Marseille 3, 1998. http://www.theses.fr/1998AIX30013.
We have investigated micro structure and defects of quasicrystalline grains by using X-ray Topography (XRT conventional or Synchrotron), Transmission Electron Microscopy (TEM) and Phase Contrast (PC) at room temperature and during annealing. XRT experiments have revealed loop shape defects in all samples (AlPdMn and AlCuFe icosahedral phase) either after growth or annealing. The annealing behaviour of this defects was followed in situ by XRT. In this case, the evolution of contrast was unusual, because it was modified with the temperature and this effect appeared completely reversible during cooling. On the other hand, a long time annealing process up to 750ʿC XRT have showed that the loop shape defects increase in size and density. Conversely, in the same sample by Electron Microscopy we did not observed loop shape defects but straight line dislocations and we did not observed any modification of dislocation contrast with temperature. Two inhomogeneities were observed by PC : dodecahedron cavities and crystalline lamellae (identified by TEM). Both of these inhomogeneities are in relation with the contrast of loop shape defects. Thereby, we have studied the character of the strain field associated with loop shape defects. This one can result either grain growth or relaxation of strains produce during germination and development of lamellae. In this context, we have suggested that loop shape defects have " phasonic " strain field
Voitot, Thierry. "Etude par microscopie à force atomique des mécanismes de plasticité dans le polypropylène isotactique." Lille 1, 2000. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2000/50376-2000-292.pdf.
Vignolle, Caroline. "Etude de films minces supraconducteurs d'YBaCuO par microscopie électronique en transmission." Grenoble 1, 1991. http://www.theses.fr/1991GRE10142.
Bardin, Olivier. "Caractérisation microstructural d'alliages Zn-Ni électrodéposés." Toulouse, INPT, 1995. http://www.theses.fr/1995INPT058G.
Perrut, Mikaël. "Etude expérimentale par observation in situ de la dynamique non-linéaire des fronts de solidification directionnelle eutectiques fibreux de l'alliage transparent succinonitrile-camphre." Paris 6, 2007. https://tel.archives-ouvertes.fr/tel-00492990.
We present an experimental investigation of the dynamics of _brous non-faceted eutectic directional-solidi_cation structures in semi-bulk samples. A transparent succinonitrile-d,camphor alloy is used. The whole structure is followed in real time using a new optical setup, which permits to observe the growth front in oblique view with a micronic resolution. The symmetry of the _brous structure is basically hexagonal. We show that a residual curvature of the isotherms causes a constant stretching of the structure, and leads to a permanent regime near the upper stability threshold (branching instability). Defects are continually generated by the branching. We also show that the lower stability threshold (_bers elimination) coincides with the Eckhaus instability threshold, as measured in thin-sample experiments. We also studied other instabilities of the _brous structure (oscillation, ovalization)
Noël, Jean-Marc. "Analyse dynamique de surfaces fonctionnelles par électrochimie localisée." Rennes 1, 2011. http://www.theses.fr/2011REN1S161.
This manuscript presents the study of the charge transfer process on modified carbon surface using electrochemical methods, and particularly the electrochemical microscopy (SECM). The substrates were modified by the electrochemical reduction of aryldiazonium salts going to the grafting of polyaryl layers, and then followed by the immobilization of different systems to study. We first studied the mechanism of the charges transfers on the surfaces functionalized with redox systems. These studies have shown a relationship between the efficiency of the electronic transfer on the surface, and the proximity between the immobilized redox moieties. Then, we studied the derivation of polyaryl layers with silver nanoparticles and with a biological molecule named glutathione. The immobilization of these non-redox systems confers new properties to the surface; the changes actually occurred in the kinetics of charge transfers. The experiments performed in different solvents have shown an influence on these processes. Finally, we have studied the reactivity of the reactive oxygen species (ROS) versus the polyaryl or glutathione modified surfaces. ROS are generated by reducing the oxygen on the surface of the microelectrode by SECM method. It was shown that the reactivity of ROS depends on the nature of the microelectrode (Platinum, Gold). The oxygen reduction on a platinum microelectrode leads to a destructive micropatterning of the organic layer. An erasable micropatterning was performed using a gold microelectrode and the antioxidant properties of glutathione
Azzam, Ahmad. "Microstructure et cinétique de précipitation dans des superalliages modèles CoAlW." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR130/document.
Superalloys are key material in aerospace industry. These materials are used to manufacturing the high temperature part of aeroengines. Currently Ni-based superalloys are the most widely used materials for high temperature applications. Researches for a new generation of superalloys with better properties have lead in 2006 to the discovery of a new stable L12 ordered, Co3(Al,W) phase embedded in the disordered γ-Co solid-solution matrix. This work aims to study the evolution of the microstructure at 900 °C and understanding the mechanism of dissolution and transformation of the γ' phase. Three different alloys with different Al/W ratios are studied here. TEM and MEB analyses are carried out on samples aged at 900 °C forvarious time. We show that γ' is a metastable phase and it dissolves in favor of B2-CoAl and D019-Co3W phases. Moreover, we highlight a mechanism of dissolution by fragmentation along the {111} close packed planes and stacking faults giving rise to D019 phase. We also study the kinetics of precipitation in the low supersaturated alloys.The early stages of precipitation of the γ' phase in a model Co based superalloy have been investigated at 900 °C using electron microscopy and atom probe tomography in the low supersaturated alloys. Nucleation, growth and coarsening stages have been studied with a focus on the temporal evolution of the precipitate composition in the light of recent theoretical developments on phase separation in multicomponent alloys. The experimental data have been confronted to the theories of nucleation and coarsening recently developed for such alloys, which are valid for non-ideal and non-dilute systems, and predict the temporal evolution of both the matrix and precipitate compositions. The rate constant for the mean size evolution of the particles, as derived from experiments, has been compared to the one predicted by the mentioned coarsening theory that accounts for a more accurate description of the thermodynamics of the phases, as compared with more classical approaches. From this comparison the γ/γ' interfacialenergy was derived and found to range between 30 and 48 mJ/m2. The exponents for the temporal evolution of average particles size, number of particles per unit volume were found identical to those for binary alloys during the coarsening regime, as expected, and the temporal evolutions of compositions in both γ and γ' phases were found to evolve as predictedby theory. Indeed, the W content in the particles, measured from atom probe tomography (APT) experiments, was found to significantly decrease with time and the observed evolution is remarkably well described by the theory and therefore is shown to originate from the competition between diffusion and capillarity
Qin, Ren-Yan. "Etude de la microtexture et de la microstructure superficielle et des propriétés physico-chimiques des surfaces des fibres de carbone." Mulhouse, 1992. http://www.theses.fr/1992MULH0235.
Garcia, Magali. "Etude de l'évolution microstructurale et dimensionnelle d'alliages réfractaires soumis à un traitement thermomécanique." Poitiers, 1999. http://www.theses.fr/1999POIT2288.
Tchana, Nkonta Daniella Vashti. "Caractérisation de l'effet de traitement de nanocristallisation superficielle (SMAT) sur un alliage CoCrMo." Thesis, Troyes, 2017. http://www.theses.fr/2017TROY0005/document.
This aims of this work is to evaluate the wear behavior of CoCrMo parts used in orthopedics. The Surface Mechanical Attrition Treatment (SMAT) method coupled with biomedical polishing has been used in this study to improve the mechanical and tribocorrosive properties of a CoCrMo alloy. In a first step, an optimization of the SMAT parameters on a CoCrMo alloy was carried out. Different surface finishing techniques were then studied to obtain an acceptable surface finish for orthopedic implants. Microstructural characterization techniques were then applied on SMATed and polished samples: scanning and transmission electron microscopy (SEM, MET), backscattered electron diffraction (EBSD), transmission kikuchi diffraction (TKD), and ray diffraction X (XRD). The results obtained showed that the SMAT treatment can create a refinement of the surface grains of the CoCrMo alloy with the presence of nano-grains in the extreme surface. Indentation measurements as well as incremental hole tests were performed. An increase of more than 30% of the hardness was observed after SMAT as well as the generation of residual surface compressive stresses. The tribocorrosive properties of the CoCrMo alloy were also studied by disk wear tests, scratch tests, and electrochemical tests before and after SMAT
Brucelle, Olivier. "Étude de l'effet de la microstructure sur la résistance à la corrosion sous contrainte en milieu primaire R. E. P. De l'alliage 718." Toulouse, INPT, 2001. http://www.theses.fr/2001INPT007G.
Deville, Sylvain. "Etude des mécanismes de renforcement et de dégradation des céramiques biomédicales à base de zircone : du macroscopique au nanoscopique : contribution de la microscopie à force atomique." Lyon, INSA, 2004. http://theses.insa-lyon.fr/publication/2004ISAL0041/these.pdf.
Les récents événements de rupture de têtes fémorales en zircone ont montré l’importance d’une compréhension des mécanismes fondamentaux de la transformation de la zircone. Par ailleurs, l’augmentation de la durée de vie des personnes soutient le besoin d’une durée de vie des prothèses beaucoup plus importante qu’actuellement. Dans ce contexte, le projet européen Bioker, dans lequel s’est inscrit ce travail de thèse, a pour but de développer et caractériser de nouveaux matériaux nanocomposites alumine zircone. Les matériaux ont été caractérisés selon deux points de vue distincts : d’une part les mécanismes de renforcement et d’autre part ceux de dégradation. La nuance retenue présente un renforcement par pontage important, dégradé en partie par la fatigue cyclique. Les seuils de propagation de fissures restent malgré tout bien supérieurs à ceux mesurés pour les céramiques biomédicales classiques, ce qui laisse augurer d’une durée de vie augmentée. En terme de dégradation, la zircone est sensible au phénomène de vieillissement. Des nouveaux paramètres critiques sur les cinétiques de vieillissement ont été identifiés, ainsi que l’influence d’une matrice stable en alumine. La microscopie à force atomique a été particulièrement mise à contribution pour analyser et mesurer avec précision les caractéristiques du relief induit par la transformation, en particulier lors des premiers stades de la transformation. En parallèle, la théorie phénoménologique de la transformation a été appliquée au cas de la zircone cériée et comparée aux mesures MFA. Au delà de la zircone, ces résultats apportent donc un nouvel éclairage sur toutes les transformations de type martensitique
Deville, Sylvain Chevalier Jérôme. "Etude des mécanismes de renforcement et de dégradation des céramiques biomédicales à base de zircone." Villeurbanne : Doc'INSA, 2005. http://docinsa.insa-lyon.fr/these/pont.php?id=deville.
David, Adrian. "Propriétés structurales et électroniques de couches minces liées aux interfaces entre perovskites." Caen, 2010. http://www.theses.fr/2010CAEN2055.
Oxides are the subject of numerous studies in the field of the chemistry of materials. The synthesis of thin films can lead to materials which can not be stabilized using classical ways of synthesis. Those materials can present original physical and structural properties resulting from the control of the electronical interactions at the interfaces. This thesis is at the boundary between solid chemistry and condensed matter. The manuscript is focused on the synthesis, the microstructure and the physical properties of functional oxide thin films. Two different studies are described. First the synthesis and the characterization of the BiCrO3 compound are studied. This material is placed in the context of the multiferroic compounds as BiFeO3 and BiMnO3. A microstructural study realised by transmission electronic microscopy revealed the presence of several crystallographic forms in the same phase. Two phases are identified as the high and low temperature phases described in the bulk. A third variant, unidentified yet, is presented as an adaptation phase generated by the substrate induced strains. A second is devoted to the study of the LaVO3/SrVO3 system, synthesized in the form of superlattices. This system is strongly correlated and it can present a metallic behaviour according to the synthesis conditions. The thin films show an unexpected ferromagnetic behaviour. Those two studies are based on a complete structural study which allows the understanding of the mechanism of interesting physical properties
Thomas, Christophe. "Microscopie à force atomique in situ et nanomécanismes de plasticité dans les polymères semi-cristallins." Lille 1, 2006. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2006/50376_2006_206.pdf.
Perrut, Mikael. "Etude expérimentale par observation in-situ de la dynamique non-linéaire des fronts de solidification directionnelle eutectiques fibreux de l'alliage transparent succinonitrile-camphre." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00492990.
Gusachenko, Ivan. "Microscopie par génération de second harmonique résolue en polarisation : développements théoriques et expérimentaux et application à l'imagerie de la microstructure du tendon pendant des essais mécaniques." Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00910146.
Keller, Clément. "Etude expérimentale des transitions volume/surface des propriétés mécaniques du nickel polycristallin de haute pureté." Phd thesis, Université de Caen, 2009. http://tel.archives-ouvertes.fr/tel-00403216.
Cocheteau, Emeline. "Conception, réalisation et caractérisation de piezorésistances ultra-minces pour des applications microsystèmes." Toulouse, INSA, 2002. http://www.theses.fr/2002ISAT0005.
This work concerns the elaboration, the physical and electric characterization of ultra-thin piezoresistive layers (lower than 100 nm) for microsystem applications obtained by ion implantation. More particularly, our study is focused on the design of piezoresistive microlevers for atomic force microscopy. After a first chapter devoted to the state-of-the-art of atomic force microscopy, we describe in the second chapter the fabrication of microlevers integrated ultra-thin piezoresistive layers. In the third chapter, we compare the theoretical and experimental results concerning the mechanical properties (resonance frequency and stiffness) and the sensitivity of detection of the piezoresistive microlevers obtained with two different fabrication processes. Measurements of noise show that two types of noise are dominating in piezoresistive microlevers : 1/f noise and Johnson noise. Our results are presented in the fourth chapter and compared to theoretical noises in ultra-thin piezoresistive layers. Based on these results, an optimization for the positioning and the doping of the piezoresistive layers is proposed without losses of detection sensitivity. In this study, we have demonstrated that ultra-thin piezoresistive layers exhibiting excellent electrical properties concerning both sensitivity and noise characteristics can be obtained by ion implantation provided the implantation and annealing conditions are optimized. Moreover, the results obtained can be used for other microsystem applications : piezoresistive pressure sensors, piezoresistive accelerometers, piezoresistive biosensors
Martinez, Ostormujof Tomas. "Apport des approches avancées en microscopie d’orientation pour l'analyse des microstructures de transformation de phase dans les aciers." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0358.
This thesis focuses on some of the latest progress in EBSD-based orientation microscopy to improve the analysis of complex steel microstructures and to contribute to a better understanding of the genesis of phase transformation induced microstructures. This is of key importance to optimize the thermomechanical processing route of steels and to improve mechanical properties. The first issue to progress in the understanding of phase transformation induced microstructures in steels was to capture the formation of high temperature austenite before complete ferrite/bainite or martensite transformation during cooling. For this purpose, in-situ EBSD heat treatments have been implemented in a SEM in complement with the well-known indirect crystallographic reconstruction. A heating module with an optimized design for the EBSD set-up has been coupled with a state-of-art EBSD camera. The result shows that high quality patterns can be acquired at temperatures around 1000°C with an indexing speed of more than 1000Hz. This allows to capture the dynamic microstructure evolution induced by phase transformation and austenite grain growth. Different cases of studies carried out with different industrial partners illustrate the performance of HT EBSD analysis, with a special focus on the analysis of the austenite grain refinement due to austempering treatments. The second issue was to apply advanced EBSD pattern analysis to complex and multiphase steel microstructures to improve the acquired orientation data in terms of indexing rate and phase discrimination (especially for phases with cubic crystal symmetry). For the classical Hough Transform (HT) based indexing approach, optimizing the reflector list per phase is the most important feature for reliable phase discrimination. The recently proposed “Refined Accuracy” (RA) approach is sensitive to difference in Kikuchi Band Width and is found to be able to discriminate cubic phases with a difference in the lattice parameter of 0.73Å. Finally, Pattern Matching approaches that compare experimental patterns to a dictionary of dynamically simulated patterns was found to offer the best performance to (1) index poor quality patterns often found in martensite/austenite islands and (2) discriminate cubic-based phases corresponding to inclusions or minor precipitates in a ferrite/austenite matrix. The best metric to compare experimental and simulated patterns is the Normalized Cross Correlation (NCC). Finally, the last issue was to progress in the automated EBSD-based discrimination of ferrite/bainite/martensite transformation products. Those phases are all indexed as ferrite-cubic phase in an EBSD map. Additional EBSD-based parameters like pattern quality and/or KAM can be leveraged to highlight differences between those phases. However, user defined threshold criteria to identify those phases is often subjective and the procedure can be time consuming. In the search of an objective and effortless approach, we have implemented Artificial Intelligence models to discriminate the phase transformation products based on pattern quality and KAM. A supervised learning method was developed using the U-Net CNN architecture to separate ferrite/upper bainite/martensite. High accuracies were reached for microstructures with similar features to those shown to the model during training, thus it is a good option for repetitive tasks. To avoid labeling, unsupervised approaches were also tested. A k-means clustering approach demonstrated a relatively good ability to discriminate upper and lower bainite using features extracted from indirect crystallographic reconstruction. On the other hand, a method called unsupervised CNN showed an excellent ability to discriminate ferrite and martensite from DP steels but it struggled with multiphase microstructures. Both unsupervised approaches provided promising results and may be used as a pre-labeling step to ease the process
Letellier, Laurence. "Etude des joints de grains et interphases dans les superalliages Astroloy par microscopie électronique et tomographie atomique." Rouen, 1994. http://www.theses.fr/1994ROUES067.
Vallée, Daniel. "Mechanical and chemical characterization of the heterogeneous microstructure of green concrete with mineral additions." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/30191/30191.pdf.
One of the main interests of the cement and concrete industries is to better understand the mechanical properties of green concrete systems. This report provides a nano-investigation approach with a one-to-one coupling of the mechanical and chemical responses of ordinary cement pastes and a cement paste with an addition of blast furnace slag. This is achieved by using the technique of nanoindentation and a quantitative investigation of the chemistry by using the scanning electron microscopy coupled with the energy-dispersive X-ray spectroscopy (SEM-EDS). The mechanical analysis includes the measurement of a relaxation coe_cient, an extension of the already known theory of the nanoindentation technique. The results are implemented with a deterministic analysis of the chemistry, a method allowing the determination of the nature of an indented area from the atomic ratios measured by using the SEM-EDS on this spot, and which can be directly linked to the mechanical responses measured by the nanoindentation tests. A statistical analysis based on the maximum likelihood estimation is also performed in order to identify the mechanical responses of the di_erent chemical phases present. It is found that the most of the microvolumes probed by the mechanical and chemical investigation are heterogeneous composites with intermixing. We could also determine the mechanical properties of monosulfoalumite and hydrotalcite combined with C_S_H, important hydration products of cements with slag additions.
Stodolna, Julien. "Étude par microscopie électronique en transmission d’échantillons cométaires de la mission Stardust." Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10046/document.
Cometary dust particles are believed to be relics of the primitive material of the early solar system. This material is now available for studies in the laboratories since the Stardust mission (NASA) brought to Earth samples from the comet 81P/Wild 2.The aim of this PhD work is to characterize Wild2 samples by TEM. Approximately one hundred picograms of cometary material have been studied. The mineralogy gives information about the formation and evolution conditions of the grains in order to reconstruct their histories. The aim is also to characterize the thermal induced modification due of the collect into the silica aerogel under hypervelocity conditions. We have characterized two categories of grains. The first consists of relatively large grains (5-10µm in average), mainly well preserved silicates. These silicates display a wide range of compositions and microstructures. The second category consists of fine grain material (<500nm). The microstructure is characteristic of thermally modified particles that have suffered strong interaction with the silica aerogel during the hypervelocity impact. A specific method has been developed to quantify the data and to understand the physical and chemical mechanisms that occurred during the deceleration into aerogel. This fine grain material has a composition close to solar abundance, showing that it did not been chemically fractionated in the protoplanetary disk before the incorporation on comet Wild2. We deduce that cometary material is made of an assemblage of relatively large grains stick together by a fine grained material with the characteristic composition of the most primitive material found into the chondritic meteorites
Auzary, Sandrine. "Etude microstructurale et détermination des contraintes dans des films minces supraconducteurs d'YBaCuO." Poitiers, 1997. http://www.theses.fr/1997POIT2268.
Ribes, Hervé. "Microstructure de composites aluminium-carbure de silicium après traitements thermomécaniques." Grenoble INPG, 1989. http://www.theses.fr/1989INPG0084.
Brochet, Stéphanie. "Compréhension du rôle de la microstructure d'aciers inoxydables austénitiques à grains fins sur le comportement en fatigue." Lille 1, 2007. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2007/50376-2007-187.pdf.
Rjimati, El Arbi. "Microfiltration tangentielle de suspensions particulaires : modélisation." Montpellier 2, 1990. http://www.theses.fr/1990MON20029.
Declairieux, Charles. "Etude microstructurale et thermomécanique d'alliages à mémoire de forme de type HfPdX et TiAuX à hautes températures de transformation." Paris 6, 2011. http://www.theses.fr/2011PA066266.
Cadel, Emmanuel. "Etude de la ségrégation intra et intergranulaire de solutés par sonde atomique tomographique et microscopie électronique en transmission." Rouen, 2000. http://www.theses.fr/2000ROUES036.
Brien, Valérie. "Etude par microscopie électronique en transmission des mécanismes de déformation d'un superalliage à base de nickel en fatigue oligocyclique à haute température." Paris 11, 1995. https://tel.archives-ouvertes.fr/tel-02985973.
In order to understand the structural mechanisms of deformation in low cycle fatigued single-crystal superalloys, total deformation imposed with R epsilon = εmin / εmax= 0 or -1, according to crystallographic axis <001> tests were carried out tests at 950 °C (1223K), at the frequency 0. 25Hz. In R epsilon = 0 fatigue, we derive a general behaviour of the microstructures of deformation according to two parameters which are the total deformation imposed and the number of cycles. Thus, a simple tension causes the localization of dislocation networks at matrix/precipitated interfaces perpendicular to <001> so that excited dislocations are those that relax the parametric deviation. The greater the total deformation imposed or the greater the number of cycles, the more homogeneous the deformation spreads out to the vertical channels. Dislocations reduce the parametric misfit between the two phases. Type N coarsening is observed at 200 cycles for small amounts of total deformation imposed. In R epsilon = -1 fatigue, we show that compression deforms the vertical channels without the formation of networks since only one deformation glide sliding system is excited. Tension always deforms the horizontal channels in the same manner as in repeated fatigue. We also show that N type coarsening (identical to that obtained in tension creep for this type of superalloy) occurs very fast, as soon as 115 cycles. The synthesis of these results, enriched with considerations on the internal stresses (coherence stresses and stresses due to parametric deviation/misfit) allowed us to propose a model of behaviour that predicts (whether in fatigue R epsilon = 0, R epsilon = -1, in tension or compression) the nature and location of the active gliding systems as well as the qualitative distribution of the internal stresses of the superalloy
Oliveira, Anicio Costa Isadora Maria. "Relations entre la microstructure, les propriétés mécaniques et électromagnétiques de fils d'acier au carbone traités thermomécaniquement." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R047.
Pearlite is a common constituent of a large variety of high strength steel grades typically used in many structural engineering applications, which demand a good combination of high strength and ductility. With the increasing requirements for product quality and in-service reliability, the non-destructive inspection of materials enables the evaluation of their properties including electromagnetic methods, such as eddy current testing (ECT). However, the influence of microstructural parameters on the physical properties indirectly measured by an electromagnetic sensor has not yet been completely elucidated. The objective of the present work is thereby to understand the relations between microstructure, mechanical properties, and electromagnetic behavior of carbon steel wires submitted to different thermomechanical treatments. It aims also at improving the knowledge of the physical and mechanical metallurgy of these steels. The effect of microstructure and plastic deformation on the electromagnetic responses of different steels with various tensile strengths was investigated through resistivity down to 2 K and magnetic measurements, as well as by ECT. In addition, magnetic domains could be imaged by magnetic force microscopy despite the complex microstructures. The electromagnetic responses changed according to the electrical conductivity and magnetic permeability variations of each material, which were mainly related to changes in the volume fraction, distribution, and morphology of the cementite phase within the α-ferrite matrix. The increase of carbon concentration enhances the localization of electrons at the atomic sites, assisting the covalent character of interatomic bonds and thereby reducing the conductivity of steels. Besides, the α-Fe3C interfaces that act as a physical barrier for dislocation slip in ferrite, affecting as well the main free-path for conductive electrons and magnetic domain walls displacements within the material. Conductivity and permeability increased in the order of martensite, sorbite, pearlite, proeutectoid ferrite-pearlite, spheroidite, and ferrite microstructures. Also, the electrical and magnetic behavior of fully pearlitic steels was observed to depend on the deformation resulted from the cold-drawing and in-service application where fatigue may occur. Low-cycle fatigue experiments have pointed out that the resistance can be managed by relevant thermo-mechanical treatments. The potentiality of ECT was highlighted as a characterization tool of the microstructural state and mechanical properties of steel wires during manufacturing processes or in-service environment. Finally, this technique has been shown to be useful for monitoring cyclic elastic deformation and plastic accommodation of pearlitic steels responding to fatigue-loading conditions
Ji, Vincent Ning Foct Jacques. "Contribution à l'analyse par diffraction des rayons X de l'état microstructural et mécanique des matériaux hétérogènes." [S.l.] : [s.n.], 2003. http://www.univ-lille1.fr/bustl-grisemine/pdf/extheses/50376-2003-177-178.
N° d'ordre (Lille 1) : 384. Résumé. Pagination multiple pour les deux volumes d'annexes. Bibliogr. à la suite de chaque chapitre.
Davoisne, Carine. "Évolution des silicates dans les milieux interstellaires, circumstellaires et cométaires : Le rôle de l'irradiation et de la température." Lille 1, 2006. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2006/50376_2006_98.pdf.
Seidametova, Gulzar. "Formation of extrusion-intrusion in a martensitic steel studied by advanced microscopies." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10163/document.
The objective of this work is to explain the mechanism of extrusion-intrusion pair formation in a 12%Cr martensitic steel during low cycle fatigue at room temperature in regards to the different interfaces creating the material complexity. The atomic force microscope analysis of the specimen surface after each interruption step of low cycle fatigue test revealed two different morphological types of extrusions that were named principal and secondary extrusions. The transmission electron microscope investigation of microstructural evolutions under the fatigue slip markings demonstrated the localization of principal extrusions in the vicinity of different martensitic boundaries as well as of fatigue dislocation cell walls, and the localization of intrusions in the boundaries or walls themselves. As for the secondary ones, their localization inside the laths was validated too. The ensemble of results together with the Polak’s model helped to propose the mechanism of formation of fatigue slip markings in the hierarchically organized martensitic steel. Thus, the existing different boundaries and the formed dislocation cells were found to play a definitive role in the creation of intrusions. As follows, the martensitic hierarchical interfaces and dislocation cell walls are considered to be a source of dislocations and at the same time a sink for vacancies
Zhao, Dan. "Study on the creep behavior of clay under complex triaxial loading in relation to the microstructure." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0372/document.
The objective of this research is to analyze the creep behavior of a typical clay along triaxial tests, moreover, to analyze the microstructural mechanisms of creep. Analysis on the macroscopic results ascertained that both dilatancy and contractancy phenomena could occur during creep. The magnitude of the dilatancy/contractancy during creep was guided by the test conditions: stress level and the over consolidation ratio, which specifically governed the direction of the volumetric strain variations. The results of SEM indicated that the microstructural evolution of the clay after the mechanical loading depend on the stress history. Afterwards, the structural evolution in creep phase depends on the structural pattern developed in monotonic loading
Maetz, Jean-Yves. "Évolution de la microstructure d’un acier inoxydable lean duplex lors du vieillissement." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0008/document.
Lean duplex stainless steels are austeno-ferritic steels with lower nickel and molybdenum contents, developed in the late 90's. Considering mechanical properties, corrosion resistance and cost of raw material, this family is an interesting alternative to standard austenitic stainless steels, which currently represent two thirds of stainless steel production. However, lean duplex steels are relatively recent and their thermal stability has been relatively little studied, especially during long term aging. In this study, the microstructural evolution of a lean duplex steel 2101 was studied during isothermal aging at temperatures between 20 °C and 850 °C, from few minutes to several months. Aging kinetics were followed by thermoelectric power measurements (TEP), from which aged states were selected to be characterized by electron microscopy and atom probe tomography. At intermediate temperatures of 350 - 450 °C, Fe-Cr demixing and precipitation of Ni-Mn-Al-Si-Cu occur in the ferrite despite the low nickel content of this grade, leading to an increase in the TEP. For higher temperatures, at about 700 °C, the mechanisms which govern the different microstructural evolutions have been described by a multi-scale approach: the nucleation and growth of M23C6 and Cr2N, observed from few minutes of aging and the σ phase precipitation, observed for longer aging time. The latter is accompanied by a transformation of δ ferrite in γ2 secondary austenite, and by the partial transformation of austenite into martensite during cooling. The effect of different phases on the TEP of the lean duplex steel can be qualitatively described during aging by a rule of mixture
Ramdani, Hamdane. "Contribution à l'étude d'aimants samarium-cobalt : relation entre les propriétés magnétiques et la microstructure." Rouen, 1987. http://www.theses.fr/1987ROUES034.
Largiller, Grégory. "Maîtrise du frittage de matériaux céramique-métal à gradients de composition et de structure." Grenoble INPG, 2010. http://www.theses.fr/2010INPG0160.
Graded materials are used to gather complementary physical and/or chemical properties into a single part. Cermet material (ceramic metal composite) developed by Rio Tinto Alcan may be used as inert anode for aluminium electrolysis. To connect these ceramic matrix materials to the current network, we propose to associate them with a conductive material in a single sintering step. Using our knowledge on powder metallurgy with microstructure analysis, thermodynamical and mechanical calculations, a new range of material called metcer (metal ceramic composite) has been developed. According to their metal phase proportion and composition, the metcer materials can be cosintered with cermets in a single sintering step. By modifying the metal phase proportion, we enabled the parts to keep joined during the whole sintering thermal cycle. The composition of oxides and metal phases change the diffusion phenomena and enable one to build a graded interface between the layers. Based on continuum mechanics, constitutive equations have been used to simulate the sintering of a cermet and a metcer. Constitutive equations have been implemented into a finite element software to identify the weak regions of bilayers parts of complex geometry. We compared numerical simulation results with optical observations made during sintering on large scale bilayers. Cracks near the interface occur at low temperature when the strain mismatch between the layers is low and the viscosities of the layers are high. Thus, the materials have a fragile behaviour. At high temperature, when the viscosities are low and the strain mismatch is high, the stresses in the vicinity of the interface are released. Combining our knowledge on the chemistry and interactions between these materials, we developed a trilayer material. This material showed up a graded interface without any crack
Boulnat, Xavier. "FAST high-temperature consolidation of Oxide-Dispersion Strengthened (ODS) steels : Process, microstructure, precipitation, properties." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0139/document.
This work aims to lighten the understanding of the behavior of a class of metallic materials called Oxide-Dispersion Strengthened (ODS) ferritic steels. ODS steels are produced by powder metallurgy with various steps including atomization, mechanical alloying and high-temperature consolidation. The consolidation involves the formation of nanoparticles in the steel and various evolutions of the microstructure of the material that are not fully understood. In this thesis, a novel consolidation technique assisted by electric field called "Spark Plasma Sintering" (SPS) or "Field-Assisted Sintering Technique" (FAST) was assessed. Excellent mechanical properties were obtained by SPS, comparable to those of conventional hot isostatic pressed (HIP) materials but with much shorter processing time. Also, a broad range of microstructures and thus of tensile strength and ductility were obtained by performing SPS on either milled or atomized powder at different temperatures. However, SPS consolidation failed to avoid heterogeneous microstructure composed of ultrafine-grained regions surrounded by micronic grains despite of the rapid consolidation kinetics. A multiscale characterization allowed to understand and model the evolution of this complex microstructure. An analytical evaluation of the contributing mechanisms can explain the appearance of the complex grain structure and its thermal stability during further heat treatments. Inhomogeneous distribution of plastic deformation in the powder is argued to be the major cause of heterogeneous recrystallization and further grain growth during hot consolidation. Even if increasing the solute content of yttrium, titanium and oxygen does not impede abnormal growth, it permits to control the fraction and the size of the retained ultrafine grains, which is a key-factor to tailor the mechanical properties. Since precipitation through grain boundary pinning plays a significant role on grain growth, a careful characterization of the precipitation state was performed on consolidated ODS steels. The experimental data obtained by transmission electron microscopy, small angle neutron scattering and atom-probe tomography evidenced the presence of dense and nanosized particles in SPS ODS steels, similarly to what is observed in conventional ODS steels. This is of great importance since it proves that the precipitation is very rapid and mainly occurs during the heating stage of the consolidation process. Using a thermodynamic model, the precipitation kinetics of Y2O3 and Y2Ti2O7 were successfully reproduced at various consolidation temperatures. Both experimental and numerical findings agree with the rapid precipitation of nanoparticles that are then extremely stable, even at high temperature. Consequently, this model can be an efficient tool to design ODS steelsby the optimization of the precipitation state
Arnoux, Michaël. "Etude du comportement en fluage à haute température du superalliage monocristallin à base de nickel MCNG : Effet d'une surchauffe." Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aéronautique, 2009. http://tel.archives-ouvertes.fr/tel-00445811.
Broussaud, Florence. "Influence de la teneur en magnesium sur la microstructure et les proprietes mecaniques d'alliages al-li-cu-mg." Paris 6, 1988. http://www.theses.fr/1988PA066110.
Leïchlé, Thierry. "Bioplume : A MEMS-based picoliter droplet dispenser with electrospotting means for patterning surfaces at the micro-and nanometer scales." Toulouse 3, 2006. http://www.theses.fr/2006TOU30267.
The need for patterning surfaces with organic or inorganic materials at a micro and nanometer scale is of crucial importance for designing novel hybrid devices with unconventional properties for photonics, electronics, biosensors, etc. Among various patterning methods, dispensing techniques relying on the use of microcantilevers are very promising for several reasons. The first one is that they permit a direct patterning of the surface with different kinds of materials without any need for prefabricated patterns. Secondly, alignment of the cantilevers with respect to specific regions on the surface is straightforward since the cantilevers themselves can be used as displacement sensors. Moreover, to overcome the serial nature of cantilever-based techniques, parallel approaches can be developed to meet specific requirements in terms of throughput and fabrication costs. Finally, electrically-assisted deposition can be envisaged provided that addressable electrodes are implemented onto the cantilevers. A fully automated MEMS designed for the trim control of a microspotting system (so called "Bioplume") using an integrated parallel force sensor with high precision and sensitivity will be presented. This microsystem improves the results, in terms of size and homogeneity of deposited droplets, through a direct-contact method. It allows the contact time and the force to be controlled during deposition. Using this method, homogeneous spots can be realized leading to a reproducible analysis. Proof-of-concept experiments have been carried out to demonstrate the versatility of our deposition system in terms of deposited materials and spot size ranging from the micro to nanometer scale. More specifically, we will discuss results obtained for surface patterning with oligonucleotides, proteins, molecular imprinted polymers, conductive polymers, nanoparticles, etc. Through direct deposition with and without electrically-assisted techniques
Bugnet, Matthieu. "Synthèse, structure électronique et comportement sous irradiation aux ions de films minces de phases MAX." Poitiers, 2011. http://theses.univ-poitiers.fr/23902/2011-Bugnet-Matthieu-These.pdf.
The aim of this work is to synthesize model materials (epitaxial thin films) of ternary ceramics called MAX phases, in order to study their behavior under ion irradiation. To follow the microstructural modifications induced by ion irradiation, we used electron energy loss spectroscopy and X-ray absorption spectroscopy in addition to X-ray diffraction and transmission electron microscopy techniques. The growth of Cr2AlC and Cr2GeC epitaxial thin films was achieved by magnetron sputtering whereas the synthesis of textured Ti2AlN layers was obtained by high temperature plasma nitriding of multilayers with an average stœchiometry Ti2:Al1:N1. The electronic structure of unirradiated films of de Cr2AlC, Cr2GeC, Ti2AlC, Ti3AlC2 and Ti2AlN was then characterized. Experimental spectra were interpreted from ab initio simulations. This study shows that structural information may be obtained from fine structures of core electron excitation edges. After irradiation, the study of the C-K and Al-K near-edge fine structures in Ti3AIC2 evidences that Ti6C octahedra layers are very resistant to irradiation damage and on the contrary, aluminium layers are strongly disordered. A similar behavior is suggested for Ti2AlC, Ti2AlN and also partly for Cr2AlC. Though titanium based materials are still crystalline after irradiation at high fluence, chronium based compounds rapidly amorphize. It is evidenced that the initial crystalline structure is recovered after post-irradiation annealing
Poupard-Potin, Annick. "Etude par microscopie électronique STEM des joints de grains dans les céramiques électroniques : application aux cas des varistances à base de ZnO et des diélectriques BaTiO3-LiF." Phd thesis, Université Sciences et Technologies - Bordeaux I, 1986. http://tel.archives-ouvertes.fr/tel-00182709.
Godon, Julie. "Influence of steel cleanliness on the wire drawing of hypereutectoid steel fine filaments." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R005.
The production of very fine filaments (60 µm in diameter) of high carbon and high strength steels remains atechnological challenge. Indeed, during the drawing of these filaments, fractures have been observed limiting theobtaining of coils of great length. This study, in collaboration with company BEKAERT NV, is to understand therole of the microstructure of steel, and more specifically the steel cleanliness on the occurrence of fracture duringwet drawing.Methodologies for inclusion identification and for inclusion count were developed. 90 % of the fractured filamentswere associated with an inclusion which was SiO2, or SiO2-CaO or SiO2-MgO. The fracture of the wires resultedfrom debonding of the inclusion from the matrix. Inclusions exhibited a wide range of sizes but mostly around6µm. The inclusion density did not appear as the only parameter that affects the fracture occurrence. An importanteffect of size and of chemical composition inclusion of the inclusions was found. A critical size of inclusions forfracture was observed but it depends on the chemical composition of inclusions. The drawing parameters also playan important role in the fracture occurrence. The wire mechanical properties and the die angle appears to beimportant parameters in view to reduce the fracture ratio.A deeper analysis of the microstructural changes around the inclusion by EBSD and modelling underlines a realimpact of the inclusion on the local deformation around the inclusion. The local analysis (TEM and ACOM -Automated Crystal Orientation Mapping) of inclusion/matrix interface shows a difference of microstructure at theinclusion edge along the drawing axis and a higher local deformation. The study of these different parametersmakes possible to propose a fracture mechanism that takes into account the part of the material subjected to shearand the one subjected to tensile stress
Trevisiol, Céline. "Effet de la microstructure et de la rugosité sur le comportement au frottement et à l’usure d’aciers faiblement alliés." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2430.
This thesis is an experimental work highlighting the effects of microstructure and roughness on friction and wear behavior of low alloy steels. That's why, low alloyed steels are carrefully selected in order to generate precise microstructures. Thus, different samples characterized by a chemical composition, a microstructure and a macro-hardness are generated and characterized tribojogically by performing friction tests. An original reflection was conducted to study the tribological behavior of the same steel with different microstructures for the same level of macrohardness. In addition, the effect of normal load on the contribution of microstructure and roughness on tribological behavior is investigated. This characterization is carried out by measurements of friction coefficient, wear rate, roughness parameters, micro-hardness and nanoindentation tests, energy dispersive analyzes, observatibns by using scanning electron microscopy and analysis of wear mechanisms. Finally, 273 configurations are studied and different trends are identified, Moreover, a comparison between the results from an experimental approach and a modeling approach of the tribological behavior of dual-phase microstructures was carried out. From this study, reflections are performed as regards the modes of the applied pressure pressure between the phases as function of roughness and normal load during the experimental friction tests
Tuel, Alain. "Caracterisation de la structure de silices de precipitation par resonance magnetique nucleaire de solide et de leur morphologie." Paris 6, 1987. http://www.theses.fr/1987PA066653.
Couvy, Hélène. "Experimental deformation of fosterite, wadsleyite and ringwoodite : implications for seismic anisotropy of the Earth's mantle." Lille 1, 2005. https://ori-nuxeo.univ-lille1.fr/nuxeo/site/esupversions/20a4058e-6551-48e6-8d30-59857aa01f67.