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Amalaraj, Akash Savio. "5D Grain Boundary Characterization from EBSD Microscopy." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/8816.
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Knowledge of the full 5-degree Grain Boundary Character Distribution (GBCD) is vital to understanding properties, such as gas diffusivity, that are dominated by grain boundary character. Surface characterization techniques, such as Electron Backscattered diffraction (EBSD), can provide only 4 of the 5 GB characteristics (the rotation between the neighboring grains, and the trace of the GB on the surface). The inclination of the GB in the direction normal to the surface is not known. A previous study indicated that the GB inclination could be recovered by correlating the Electron Backscattered patterns (EBSPs) of sample points near the GB with EBSPs taken from the centers of the neighboring grains. The resultant transition curve could be compared with theoretical curves obtained from MonteCarlo simulations of electron yield from the two grains. However, a practical method based upon this study was never implemented. Here, a few microscopy and image filters have been applied to the EBSPs to improve the image quality. Also, several experiments have been conducted to verify and validate the interaction volume of the materials used to produce theoretical transition curves, in order to receive more accurate results. In this work, it is hypothesized that transition curves obtained from considering individual band intensities from the EBSPs will give more informative transition curves. The filtered EBSPs from the band intensities coupled with the accurate interaction volume values, should give us more reliable and repeatable transition curves, and that a more detailed comparison of the experimental and simulated transition curves will give higher fidelity results, in terms of GB inclination determination.
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Tong, Vivian Suetto. "EBSD characterisation of heterogeneous microstructures in zirconium alloys." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/55106.
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This thesis explores heterogeneous deformation and grain growth behaviour in zirconium alloys using electron backscatter diffraction techniques. Zirconium alloys are widely used for nuclear power applications and controlling microstructure during manufacture of reactor parts is critical for safe operation of the nuclear reactor. Mechanisms for the formation of abnormally large ‘blocky alpha’ grains in Zircaloy-4, which forms when annealing lightly deformed Zircaloy-4 within the alpha phase, have been explored using uniaxial compression and three point bending. The presence of blocky alpha is a known industrial problem, and adversely affects reactor safety, though there are limited studies addressing this problem. It was found that blocky alpha nucleates via strain induced grain boundary migration and grows via abnormal grain growth. In the presence of a strain gradient, blocky alpha grains nucleate in highly strained regions and grow towards lower strained regions. The final orientations of the blocky alpha grains depend on the pre-annealing strain state. High resolution electron backscatter diffraction (HR-EBSD) has been used to characterise microstructures before and after annealing to produce blocky alpha. To validate observations of increased dislocation density near grain boundaries, the effect of pattern overlap near grain boundaries on accuracy of HR-EBSD measurements is quantified. It was found that HR-EBSD measurements do not produce significant artefacts in this case. A simple calibration model and experiment is described to enable the extent of pattern overlap to be measured in other set-ups. Twinning behaviour in commercially pure zirconium was studied as a function of texture and strain rate. Twin types preferentially activated under high strain rate (10^3 s-1) and quasi-static strain rate (10^-3 s-1) were characterised using electron backscatter diffraction (EBSD) post-processing software. This software was written in-house and explanations of the algorithms used to identify twin boundaries and map intragranular misorientations have been included in this thesis.
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Friedbaum, Samuel Searle. "Studies of Dislocation Density Quantification Via Cross-Correlation EBSD." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8115.
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One conventional method for studying dislocations uses the Transmission Electron Microscope (TEM), a complex and expensive piece of equipment which requires extensive specimen preparation in order to thin the specimens to electron transparent thickness. Newer High Resolution Electron Backscatter Diffraction (HREBSD) methods of determining geometrically necessary dislocation content via cross-correlation promise to be able to produce estimates of the dislocation density of the sample over a larger area with considerably less preparation time and using a much more accessible instrument. However, the accuracy of the new EBSD technique needs more experimental verification, including consideration of possible changes in the specimen dislocation density due to the different preparation methods. By comparing EBSD and TEM dislocation measurements of Electron Transparent platinum specimens prepared using the Focused Ion Beam (FIB), along with EBSD dislocations measurements of specimens prepared by both FIB and mechanical polishing techniques, this paper seeks to verify the accuracy of the new method and identify any changes in the specimens’ apparent dislocation density caused by the different preparation processes.
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Villert, Sébastien. "Analyse des déformations élastiques locales par la technique EBSD." Saint-Etienne, EMSE, 2008. http://www.theses.fr/2008EMSE0030.
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La quantification locale des contraintes est un axe de recherche majeur dans l'industrie microélectronique. Dans les lignes d'interconnexions de cuivre par exemple, les contraintes résiduelles participent à la formation et à la propagation de phénomènes liés à l'électro-migration, qui nuisent à la fiabilité des lignes. Étant donnée la faible largeur de ces lignes de l'ordre de quelques centaines voire dizaines de nanomètres, il est nécessaire de mettre au point des techniques de mesure des déformations avec une bonne résolution spatiale (inférieure à 50nm). Les contraintes sont alors calculées par application de la loi de comportement du matériau étudié. L'analyse bibliographique de différentes techniques de mesure de déformations élastiques locales montre que l'EBSD offre un des meilleurs compromis entre résolution spatiale et facilité de mise en oeuvre. D'ailleurs, cette technique est déjà utilisée pour caractériser la microstructure des lignes d'interconnexions de cuivre. La mesure de déformations élastiques par EBSD repose sur la comparaison de deux clichés de diffraction (un des clichés sert de référence) par la technique de corrélation d'images numériques. Dans nos travaux, nous reprenons cette méthode et nous en améliorons la précision de mesure. Nous proposons notamment une meilleure procédure de minimisation et optimisons la corrélation d'images. L'utilisation de diagrammes d'EBSD simulés permet dans un premier temps de mettre au point notre méthode et d'en estimer les performances théoriques. Nous étudions en particulier la précision de mesure et la sensibilité à divers paramètres expérimentaux. Ensuite, deux essais spécifiques sont réalisés pour valider notre méthode sur des diagrammes expérimentaux : la flexion quatre points d'un monocristal de silicium et l'étude de dépôts de SiGe sur substrat de silicium. Enfin, notre méthode est appliquée pour déterminer les déformations et rotations dans des lignes d'interconnexions de cuivre. Cette dernière étude révèle la nécessité d'une mesure absolue (c'est-à-dire sans diagramme de référence), pour laquelle nous proposons une perspective encourageanteThe quantification of local stresses has become a major field of research for microelectronic industry. In copper interconnects for example, the residual stresses contribute to the formation and growth of voids and hillocks which lead to the interconnect failure. Since the width of interconnects has steadily decreased, strain measurement methods with a good spatial resolution (< 50 nm) are required for device characterization. Several techniques have been recently developed to this aim, such as Convergent Beam Electron Diffraction, KOSSEL micro-diffraction, high resolution X ray diffraction, micro-Raman, Electron BackScatter Diffraction , etc. . . The latter technique offers a good spatial resolution and ease of use. Indeed, it has been already used to study the microstructure of copper interconnects. The elastic strain measurement by EBSD is based on the comparison of two diffraction patterns (one is considered as reference) using digital image cross-correlation. In our work, we also use this approach to which we bring several modifications to improve the measurement accuracy. To this aim, we propose an improved minimisation procedure and we optimised the cross-correlation algorithm. In order to develop and optimise the method, a program which simulates EBSD patterns has been created. This software enables fast simulations of EBSD images for strained materials given that it considers the influence of the displacement gradient tensor (assuming small shape changes). The theoretical performances of the method are so firstly discussed. Then, we realised two specific experiments to validate the method : the four-point bending of a silicone single crystal and the tetragonal distortion of SiGe layers on silicone substrates. Finally, we apply the method to study elastic strains and rigid body rotations in copper interconnects
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Babinský, Tomáš. "Rekrystalizace automatové oceli studované technikou in-situ SEM/EBSD." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378404.
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Placing recrystallization annealing in a manufacturing proces is often necessary in order to restore plasticity of worked blanks right before working products to its final shape. For better understanding of processes which are taking place in a material during annealing the use of in-situ techniques is favorable. Such observations enable us to watch changes in the materiál in real time at the original spot. Observations at grain-level are ideally made with scanning electron microscope – SEM by electron back-scattered diffraction – EBSD. The technique makes watching nucleation, growth and potential coarsening of recrystallized grains possible. Special construction of a tensile stage allows us to watch changes of a sample during tensile tests which can be used in observing influence of MnS inclusions on plasticity of free-cutting steels. Materials studied in this work are commonly used free-cutting steel 11SMnPb30 and its lead-free alternative 11SMnBi30.
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Ondračka, Václav. "Užití elektronové difrakce k mapování elastického napětí." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-449747.
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Electron backscatter diffraction is a method that is well described and commonly used for orientation image mapping, including grain size estimation. The use of this method for measuring elastic deformation and rotations caused by plastic deformations is not so well decribed. This diploma thesis first describes the typical EBSD system. The information regarding the standard coordinate systems, grain orientation notation and system calibration is then used to create an open-source software for mapping elastic deformations and rotations inside a single grain or a monocrystal. This software uses data acquired during standard EBSD mapping on a commercial system.
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Enstad, Anne-Jorunn. "EBSD-karakterisering av et HSLA-stål under in situ varmebehandling." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16317.
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Ved sveising av HSLA-stål (High Strength Low Alloy) designet for lavtemperatur applikasjoner kan det dannes lokale sprø soner som martensitt/austenitt-faser (MA-faser). Det er derfor ønskelig å karakterisere austenitten som dannes ved tosykel sveising for å gi økt kunnskap om endringene som oppstår i mikrostrukturen.Denne masteroppgaven tar for seg karakterisering av et 420 MPa HSLA-stål ved in situ varmebehandling opp til tofaseområdet for austenitt og ferritt i kombinasjon med diffraksjon av tilbakespredte elektroner (Electron Backscatter Diffraction - EBSD). Målet med oppgaven var da å karakterisere endringer som oppstår i mikrostrukturen til stålet under in situ oppvarming i mikroskopet. Oppvarmingen ble utført ved å videreutvikle et tidligere varmebord. Stålprøvene ble ènsykel sveisesimulert til 1350 °C og avkjølt med Δt8/5. Den in situ varmebehandlingen tilsvarte da den andre sveisesykelen i en tosykel sveisesimulering. Ved prøvepreparering ble prøvene elektropolert med to ulike elektrolytter; Struers A2 og AC2. I oppgaven ble det benyttet offline-EBSD da det var nødvendig med høy skannehastighet slik at tiden for hvert EBSD-skann ble så liten som mulig.For å nå tofaseområdet til HSLA-stålet var det nødvendig å varme opp til en prøvetemperatur på over 740 °C. Da ovnen har en maksimaltemperatur på 800 °C ble det benyttet en vakuumkompatibel platinamaling mellom prøven og ovnen i varmebordet for å øke varmeledningen. Temperaturforskjellen mellom prøven og ovnen ble da reduseres helt ned til 10 °C. Det ble varmet opp til prøvetemperaturer på 750 °C, 760 °C, 770 °C, 780 °C og 790 °C. Det var nødvendig å vente i 10 minutter etter å ha nådd ønsket prøvetemperatur før det ble kjørt EBSD på grunn av termisk ekspansjon av prøven.Austenitten som ble dannet under oppvarming vokste frem langs korngrenser og hadde en orienteringssammenheng med BCC-matriksen rundt som oppfyller Kurdjomov-Sachs. Det ble observert at austenitten som dannes gradvis forsvant igjen ved økende holdetid ved høy temperatur som følge av avdamping av karbon fra prøveoverflaten. Ved oppvarming viste det seg at det ble dannet en mye større andel austenitt i prøver elektropolert med Struers AC2 enn den med Struers A2. Det ble da konstruert fasediagram for tofaseområdet til stålet på bakgrunn av andel dannet austenitt ved oppvarming. Disse viste at prøver elektropolert med Struers A2 gav mest korrekt andel austenitt.
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Rølvåg, Line Kathinka Fjellstad. "EBSD undersøkelser og in situ strekktesting av stål i SEM." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19246.
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Denne masteroppgaven har tatt for seg undersøkelser av stål designet for lavtemperaurappliksjoner ved bruk av elektronmikroskop i kombinasjon med diffraksjon av tilbakespredte elektroner (Electron Backscatter Diffraction - EBSD). Målet med oppgaven var å bruke EBSD-teknikken i kombinasjon med in situ deformasjon og en spesiallaget kaldfinger for å kunne studere materialene ved lave temperaturer. To ulike stål ble undersøkt; et smidd finkornet strukturelt stål (F70) og et varmvalset supermartensittisk rustfritt stål (Supermartensitic Stainless Steel - SMSS).F70-stålet ble sveisesimulert for å oppnå en mikrostruktur tilsvarende interkritisk grovkornet HAZ (Heat Affected Zone). Dette ble gjort ved en tosykel sveisesimulering. Prøvestaver av materialet ble varmet opp med en ønsket makstempertur på Tp1= 1350°C og Tp2= 780°C. For å undersøke effekten av ulike avkjølingshastigheter ble halvparten av prøvestavene avkjølt med Dt8/5 = 5 sekund, og den andre halvparten med Dt8/5 = 15 sekund. Ved sveising av stål kan det dannes lokale sprø soner som martensitt/austenitt-faser (MA-faser). Bilder tatt i lysmikroskop viser at strukturen til sveisesimulert F70-stål består av martensitt og noe bainitt. MA-faser er lokalisert langs korngrensene.EBSD-teknikken krever at materialet på forhånd gjennomgår en tilfredsstillende prøvepreparering for å gi gode resultater. Det var tidligere etablert en tilfredsstillende prepareringsteknikk for SMSS. I denne oppgaven ble to ulike prepareringsmetoder testet på sveisesimulerte prøver av F70-stål, som er et forholdsvis nytt materiale. Metodene som ble testet var ionesputtering og elektropolering. Preparerte prøver ble undersøkt med EBSD for å analysere kvaliteten på prepareringen. Det viste seg at MA-fasene reagerte annerledes på prepareringen enn resten av strukturen, og det var derfor vanskelig å få disse fram på EBSD-skann. De to prepareringsmetodene ga også forskjellige utfall for andel austenitt (g-fase) i stålet. Da det i hovedsak er MA-fasene som er interessante ved in situ undersøkelser ble det besluttet å ikke gjennomføre disse på F70-stålet, da en tilfredsstillende preparering må etableres først. Ved bruk av EBSD-teknikken kan orienteringsdataene som lagres behandles i programvaren TSL OIM Analysis 5.32, som tilbyr ulike renseoperasjoner. Grain CI Standarization gir alle punktene i et korn, innenfor en gitt vinkeltoleranse, samme CI-verdi som den maksimale CI-verdien funnet blant punktene i dette kornet. Det er også mulig å legge på et CI-filter som fjerner alle punkter med en CI ≤ 0,05, og erstatter disse med svarte eller grå piksler. Effekten av disse to operasjonene ble undersøkt på et EBSD-skann av SMSS tatt ved romtemperatur, uten noe form for deformasjon. Renseoperasjonene førte til at 8,1 % av alle punkter ble fjernet. 3,8 % av disse var av g-fasen, som utgjør kun 17,3 % av skannet før renseoperasjonene ble benyttet. Punkter som fjernes ligger i hovedsak i forbindelse med korngrenser eller øyer av restaustenitt. For SMSS som inneholder rundt 20 vol.% restaustenitt i opprinnelig (dvs. interkristisk glødet) tilstand, ble det gjennomført undersøkelser av deformasjonsindusert fasetransformasjon ved bruk av in situ strekktesting med påfølgende EBSD karakterisering. Undersøkelsene ble utført ved romtemperatur og -80°C. Et spesiallaget strekkbord ble montert på SEM (Scanning Electron Microscope) stagen med prøven fastmontert, og en kaldfinger ble brukt for å kjøle ned prøven. EBSD karakteriseringen ble foretatt uten deformasjon og ved 1, 2, 3 og 4 % forlengelse. En sammenligning av resultatene ved romtemperatur og -80°C ble deretter utført. Det ble konkludert med at øyer av restaustenitt transformeres til martensitt som følge av plastisk deformasjon i større grad ved -80°C, som følge av høyere termodynamiske drivkrefter for reaksjonen. Ved romtemperatur var det mulig å verifisere at martensitten som ble dannet oppfyller Kurdjomov-Sachs kriteriet som beviser at den er korrekt indisert. Dette var vanskelig å verifisere for lavtemperatursforsøkene, da skannene har en mye lavere kvalitet.
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Ng, Christopher 1983. "Determination of special boundary coordination at quadruple nodes using EBSD." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32845.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references (leaf 21).
Grain boundaries are known to play an important role in materials properties including corrosion and cracking resistance. Some grain boundaries are resistant to corrosion and cracking and are known as "special" boundaries. While the structure of individual grain boundaries is important, the connectivity of the grain boundaries largely determines the properties of a bulk material. The coordination and connectivity of special grain boundaries have previously been studied in two dimensional grain boundary networks and are quantified by the triple junction distribution (TJD), which has been found to be non-random. The study of connectivity has been extended to three dimensions and simulations have previously been done to obtain a quadruple node distribution (QND) which was also non-random. Using Electron Back-Scattered Diffraction to characterize grain boundaries in copper and aluminum, this project obtains an experimental quadruple node distribution and verifies that it too is non-random.
by Christopher Ng.
S.B.
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Kacher, Josh. "Cross-correlation-based texture analysis using kinematically simulated EBSD patterns /." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd2994.pdf.
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Kacher, Joshua Peter. "Cross-Correlation-Based Texture Analysis Using Kinematically Simulated EBSD Patterns." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1746.
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The development and example applications of a new EBSD-based texture analysis system are presented. This new system uses the cross-correlation function to compare two EBSD patterns at a number of corresponding regions in each pattern to calculate the deformation gradient tensor. Bragg's Law-based simulated EBSD patterns are used as reference patterns in the cross-correlation method to enable the measurements of absolute elastic strain and lattice orientation at discrete points in a crystalline sample. The resolution limits of this new method are explored using a variety of computational and physical experiments. The simulated pattern method is estimated to be able to measure lattice orientations to within +/-0.02° and elastic strains to within +/-3.6x10-4 for small strains and +/-1x10-3 for large strains. Two example applications are demonstrated. The first demonstration is estimating the dislocation density in a 5.5% compressed Mg-based AZ91 alloy. Nye's and Kröner's formulations are used to estimate the dislocation density. Comparisons are made with traditional OIM measurements and it is found that the simulated pattern method offers an order of magnitude improvement in dislocation density estimations over OIM. The second demonstration is tetragonality measurements of HSLA 65 steel along the weld line of a friction stir welded plate. Accurate tetragonality measurements in the bainite phase of the steel can be made using information from the diagonal components of the elastic strain tensor. The measured tetragonality can be related to the concentration of interstitial carbon atoms in the iron lattice to find the carbon distribution in the sample. From these experiments, it is demonstrated that the simulated pattern method presents a new and powerful methodology for texture analysis that exhibits both ease of use and access to high resolution orientation and elastic strain data.
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Pešina, Zbyněk. "Analýza deformačně indukovaných změn fázového složení oceli TRIP metodou EBSD." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228272.
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The diploma thesis deals with phase composition measurement of the TRIP steel, using EBSD method. The steel was delivered as thermo-mechanically treated via two different routes. The phase composition of the steel was examined during gradual plastic deformation in the range 0 to10.99%. One route of thermo-mechanical treatment exhibited good agreement with the literature in terms of measured fraction of the retained austenite (15.6%) as well as its decrease during the deformation (to 8.9% at the maximum imposed strain). The samples of the second route did not show any agreement in either of the parameters spoken.
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Blaineau, Pierre. "Restitution de la microtexture parente à partir de la microtexture héritée mesurée par EBSD : une application aux aciers faiblement alliés." Thesis, Metz, 2010. http://www.theses.fr/2010METZ042S.
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L’état métallurgique de l’austénite avant le dernier refroidissement (taille de grain, texture, écrouissage …) ne peux pas directement être caractérisée car elle se transforme lors du dernier refroidissement or elle influence remarquablement les propriétés d’emploi des aciers. Ce travail de thèse propose une méthode automatique indirecte pour restituer la microtexture austénitique à partir de la seule information de la microtexture, mesurée par EBSD, des phases héritées (martensite, bainite) à basse température. Cette méthode nécessite trois prérequis : 1) La présence d’une relation d’orientation entre l’austénite parente et le produit de transformation 2) la phase héritée s’est formée dans le grain avec lequel elle est en relation d’orientation et 3) il y a un nombre de variant suffisant. Sa validation a été effectuée sur des exemples numériques et pour les aciers faiblement alliés. La restitution des contours austénitiques est efficace mais sensible aux variants en relation d’orientation avec plusieurs grains parents adjacents. Ces situations ambigües sont principalement générées par la présence de macles dans la phase parente ou par sélection de variants aux joints de grains austénitiques. Dans ce cas, il est possible d’améliorer la qualité de la restitution des contours parents (notamment les contours de macles) en prenante en compte des informations topologiques. Ces méthodes de restitution permettent par conséquent de repérer les macles ou la sélection de variants aux joints de grains γ et donc de mieux analyser les mécanismes d’héritage de texture locale. Donc les méthodes développées peuvent être généralisées à d’autres transformations de phaseThe metallurgical state of the austenite before the last cooling (grain size, texture, strain hardening ...) cannot be directly characterized because the austenite transforms during the last cooling. However, it influences remarkably the in use properties of steels. This thesis proposes an indirect automatic method to restore the austenitic microtexture from the microtexture of the inherited phases (martensite, bainite) at low temperature, measured by EBSD. This method requires three prerequisites: 1) the presence of an orientation relationship between the parent austenite and the transformation product, 2) the inherited phase has to be formed in the grain with which it is related and 3) there is a sufficient number of variants. Its validation has been performed both on numerical examples and for low alloyed steels. The restitution of austenitic grain boundaries is efficient but sensitive to variants in orientation relationship with several adjacent parent grains. These ambiguous situations are mainly generated by the presence of twins in austenite grains or by selection of variants at the austenitic grain boundaries. In this case, it is possible to improve the quality of the restitution of the parent contours (especially the twins boundaries) by taking into account topological information. These restitution methods consequently allow to identify twins or variant selection at grain boundaries and thus to better analyze local texture inheritance mechanisms. Therefore, the developed methods can be generalized to other phase transformations
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Hansen, Landon Thomas. "Characterization of Dislocation - Grain Boundary Interactions Through Electron Backscatter Diffraction." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7536.
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Further understanding of dislocation-GB interactions is critical to increasing the performance of polycrystalline metals. The research contained within this dissertation aims to further dislocation-GB interaction understanding through three research studies. First, the effect of noise in EBSPs on GND calculations was evaluated in order to improve dislocation characterization via HR-EBSD. Second, the evolution of GNDs and their effects on back stress was studied through experimental and computational methods applied to tantalum oligo specimens. Third, statistical analysis was used to evaluate grain parameters and current GB transmission parameters on their correlation with dislocation accumulation.
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Cocle, Jennifer. "Development of the EBSD Intensity Response for Quantitative Strain Analyses of Materials." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=93017.
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Electron BackScattered Diffraction (EBSD) systems can be considered as a tool providing three kinds of responses: EBSD patterns (EBSPs) themselves, an indexing response (orientation data), and an intensity response (also called Band Contrast "BC", Image Quality "IQ", or Pattern Quality "PQ or P"). This work focused on the characterization and development of the intensity response. For now, the intensity response cannot be used for quantitative microstructural analyses, including strain analyses of materials. Indeed, this response is affected by several material and experimental conditions. Moreover, properties of the intensity response (strain sensitivity, reproducibility, exact relation with EBSP quality or diffraction band intensities) are not well-known and understood. This project constitutes an exploratory study on the development of the intensity response for quantitative strain analyses of materials. A new modelling and statistical approach is presented and assessed for transforming the raw (current) intensity response (values and grey-tones of intensity images) of commercial EBSD systems into an accurate and reproducible parameter allowing objective visualization and measurements of strain.Les systèmes de diffraction des électrons rétro-diffusés (EBSD) peuvent être considérés comme un outil offrant trois types de réponses: les patrons EBSD (EBSPs), la réponse d'indexation (données d'orientation) et la réponse d'intensité (aussi appelée Contraste de Bande «BC », Qualité d'Image « IQ », ou Qualité de Patron « PQ ou P »). Le présent projet s'est concentré sur la caractérisation et le développement de la réponse d'intensité. En effet, pour l'instant, la réponse d'intensité ne peut être utilisée pour réaliser des analyses microstructurales quantitatives des matériaux. En effet, cette réponse est influencée par de nombreux facteurs relatifs au matériau analysé et aux conditions expérimentales utilisées. De plus, les propriétés de la réponse d'intensité (sensibilité à la déformation, reproductibilité, relation exacte avec la qualité des EBSPs ou les intensités des bandes de diffraction) ne sont pour l'instant pas bien connues ni même compnses. Le présent projet représente donc une étude exploratoire visant le développement de la réponse d'intensité des systèmes EBSD commerciaux pour l'analyse quantitative de la déformation des matériaux. Dans ce projet, une approche de modélisation statistique est présentée et évaluée afin de transformer la réponse d'intensité actuelle (valeurs et tons de gris des images d'intensité) des systèmes EBSD commerciaux en une réponse précise et reproductible permettant de visualiser et de mesurer objectivement la déformation.
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Ruggles, Tim. "Characterization of Geometrically Necessary Dislocation Content with EBSD-Based Continuum Dislocation Microscopy." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/4392.
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Modeling of plasticity is often hampered by the difficulty in accurately characterizing dislocationdensity on the microscale for real samples. It is particularly difficult to resolve measureddislocation content onto individual dislocation systems at the length scales most commonly of interestin plasticity studies. Traditionally, dislocation content is analyzed at the continuum levelusing the Nye tensor and the fundamental relation of continuum dislocation theory to interpret informationmeasured by diffraction techniques, typically EBSD or High Resolution EBSD. In thiswork the established Nye-Kroner method for resolving measured geometrically necessary dislocationcontent onto individual slip systems is assessed and extended. Two new methods are alsopresented to relieve the ambiguity of the Nye-Kroner method. One of these methods uses modifiedclassical dislocation equations to bypass the Nye-Kroner relation, and the other estimates the bulkdislocation density via the entry-wise one-norm of the Nye tensor. These methods are validatedvia a novel simulation of distortion fields around continuum fields of dislocation density based onclassical lattice mechanics and then applied to actual HR-EBSD scans of a micro-indented singlecrystals of nickel and tantalum. Finally, a detailed analysis of the effect of the spacing betweenpoints in an EBSD scan (which is related to the step size of the numerical derivatives used in EBSDdislocation microscopy) on geometrically necessary dislocation measurements is conducted.
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Bjerkaas, Hans. "Characterisation and Plasticity in Extruded Al-Mg-Si Profiles engaging In-situ EBSD." Doctoral thesis, Norwegian University of Science and Technology, Department of Materials Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1647.
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A comprehensive characterisation and study of plasticity in two extruded Al-Mg-Si profiles has been carried out. The primary objective of the experimental work has been directed towards obtaining an improved understanding of the operating deformation mechanisms and mechanical anisotropy observed on all length scales during plastic deformation. In-situ deformation in the SEM combined with EBSD investigations has been an important tool in order to obtain this objective. The experimental results have been divided into two separate parts. Part A covers the characterisation and mechanical anisotropy investigations, while Part B covers the more detailed in-situ investigations.
Two alloys, one with a recrystallized microstructure and the other with a nonrecrystallized (fibrous) microstructure, have been subjected to a detailed characterisation concerned with mechanical anisotropy, through-thickness variations and effects of various heat-treatments. The experimental investigations showed that both alloys possess highly anisotropic properties. The effects of temper designation, directional dependency and position through the thickness were studied.
The in-situ deformation studies gave new insights into the fundamental reasons for the observed mechanical anisotropy and the related deformation mechanisms. Detailed investigations of the slip traces in combination with calculated Schmid value distributions provided information on potential slip activity for the various slip systems. It was found that the number of slip systems activated was very heterogeneous and this number can even vary from region to region within one individual grain. In other words, the strain distribution seemed very heterogeneous. Further, the actual number of activated slip systems was in general less than predicted by the widely used Taylor model. Consequently, if the accuracy of texture-based calculations should be improved, more advanced models like the GIA (Grain Inter-Action) and the LAMEL models should be applied.
It was also found that crystallographic orientations having a [100] or a [111] parallel to the deformation direction (DD) were more stable during simple tension deformation. Moreover, crystallographic orientations not having this configuration rotated in order to align the DD to one of the above directions. Also the rotation of individual grains seemed to have a strong relationship to the actual activation of slip systems.
The mechanical anisotropy and shape tolerances could be explained in terms of crystallographic texture, i.e. variations in the actual activation of slip. As a result, the macroscopic properties (e.g. mechanical anisotropy) were to a large extent controlled by the mechanisms operating at the microscopic length scale. A full understanding of the operating mechanisms should therefore involve exact information from all length scales.
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Pedersen, Jonas Hovde. "In situ strekkforsøk med EBSD karakterisering av HSLA-stål ved romtemperatur og -60 °C." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16316.
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Denne oppgaven har tatt for seg et 420 MPa HSLA stål. Stålet ble sveisesimulertfor å oppnå mikrostruktur tilsvarende grovkornet og interkritisk grovkornetHAZ. Interkritisk grovkornet HAZ ble oppnådd ved en tosyklus sveisesimuleringhvor materialet ble varmet opp til 1350 °C og avkjølt med Δτ8-5 = 15s og deretter gjenoppvarmet til 780 °C og avkjølt med Δτ 6-4 = 17s. Grovkornet HAZ ble oppnådd ved ensyklus sveisesimulering hvor materialet ble varmet opp til 1350 °C og avkjølt med Δτ 8-5 = 15s.Et eksempel på EBSD teknikken er vist ved en sammenligning av sekundærelektronbilde, fasekart og Image Quality kart. Sekundærelektronbilde og EBSD skannet er fra nøyaktig det samme område. På denne måten blir det demonstrert at EBSD teknikken er et verdifullt verktøy for å skille ulike stålfaser fra hverandre.Det ble så fortatt en grunnleggende EBSD karakterisering av de to sveisesyklusene. Fire skann med et totalareal på 150 µm x 150 µm ble gjort på hver av de to prøvene. Det ble konkludert med at den største forskjellen var øyer av restaustenitt som i gjennomsnitt utgjorde 2,45 % av det skannede område på tosyklus sveisesimulert prøve. I ensyklus sveisesimulert prøve var disse øyene så godt som fraværende.For tosyklus sveisesimulert stål ble det også gjennomført in situ strekktesting med påfølgende EBSD karakterisering ved -60 °C og romtemperatur. En spesiallaget kaldfinger ble videreutvilket for å kjøle ned prøven til -60 °C, da det ikke lykkes å nå -60 °C slik den opprinnelig var konstruert. EBSD karakterisering ble foretatt uten deformasjon og ved 1 %, 2 %, 3 % og 4 % forlengelse av stålet. En sammenligning av resultatene ved -60 °C og romtemperatur ble gjort. Det ble konkludert med at øyer av restaustenitt transformeres til martensitt som følge av plastisk deformasjon i større grad ved -60 °C enn ved romtemperatur som følge av høyere termodynamiske drivkrefter.Ved in situ undersøkelser må strekkbord og kaldfinger monteres i mikroskopet, dette fører til at det tar mye lengre tid å pumpe vakuum enn ved normale omstendigheter. Det tar 50 minutter å pumpe 2,5 x 10-6 mBar vakuum i tomt prøvekammer. Tilsvarende vakuum ved in situ undersøkelser tar over 5 timer å pumpe, grunnet større overflate inne i mikroskopet. Til slutt ble det gjennomført en sammenligning ved bruk av 1° og 2° Θ steglengde ved indisering av EBSD rådata. Indisering med 1° Θ steglengde ga 1,5% austenitt, mens 2° Θ steglengde ga kun 0,9% austenitt. Konklusjonen var at 2° Θ steglengde ikke oppdager de minste kornene på grunn av for grov omregning i Hough transformasjonen.
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Hansen, Kristoffer Werner. "Phase Transformation Study of X70 Steel by EBSD during In Situ Heating and Quenching." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18909.
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Arctic steels, like the API X70 steel explored in this master thesis, are developed to withstand very low temperatures, with a ductile/brittle transition temperature below −60◦C. However, during welding, brittle phases like martensite-austenite (M-A) islands may form in the heat affected zone (HAZ). In this master thesis in situ heat treatment and quenching experiments have been combined with electron backscatter diffraction (EBSD) inside a field emission scanning electron microscope in order to simulate a second weld cycle simulation. In conjunction with this a quenching device has been designed with respect to an existing hot stage.Inside the SEM, it was found difficult to recreate the characteristic microstructure of API X70 steel from a traditional second cycle thermal weld simulation. This was probably due to the slow heating rate and the excessive high temperature holding time. The developed quenching device was based on gas quenching and produced a steel sample cooling time from 600◦C to 400◦C, ∆t6/4, of approximately 6.5 seconds in every experiment. As a result of the gas quenching substantial amounts of oxide contamination, covered the sample surface following the experiments. This contamination layer produced artifacts, such as unreasonable amounts of austenite in the EBSD phase maps.Despite the quenching, islands of austenite (FCC) observed at elevated temperatures transformed into a low strain BCC structure. Some austenite islands showed a memory- effect during phase transformation, while others adapted the orientation of the surround- ing structure. No retained austenite was observed in the API X70 steel after the in situ gas quenching, probably due to insufficient cooling rates.
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Larsen, Kristian. "In situ strekktesting og karakterisering av et 9%Ni-stål : ved hjelp av EBSD." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20443.
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Denne oppgaven har tatt for seg karakterisering av mikrostruktur og in-situ strekk-testing for et 9%Ni-stål levert av JFE Steel. Dette ble gjennomført ved hjelp av EBSD og et spesialprodusert strekkbord for bruk inne i SEM. Det ble også brukt en spesialprodusert kaldfinger for å kunne kjøre in-situ strekktesting ved -60 °C. Ved hjelp av dette var målet å se hvordan mikrostrukturen til dette 9%Ni-stålet utvikler seg med økende grad av forlengelse. Først ble det lagt ned mye arbeid i å finne en prøvepreparering som ga reprodu- serbare resultater for EBSD-karakterisering. Deretter ble det gjort flere forsøk for å etablere et grunnlag for hvordan mikrostrukturen til et 9%Ni-stål faktisk ser ut. Deretter ble det gjennomført in-situ strekktesting hvor det ble tatt EBSD-skann av samme område ved 2%, 4%, 6% og 8% forlengelse. Deretter ble det gjennomført ett in-situ strekkforsøk ved -60 °C, som siden det bare ble ett eksperiment ikke med sikkerhet kan sees på som representativt. Det ble fastslått at mikrostrukturen til dette 9%Ni-stålet i all hovedsak er en seigherdet martensittisk mikrostruktur. Ved strekkforsøkene ble det ikke funnet noen konkrete fenomener som med sikkerhet kan forklare hvorfor 9%Ni-stål har så gode lavtemperaturegenskaper, og det ble ikke observert noen markant forskjell på strekktesting ved romtemperatur og -60 °C. Det ble også gjennomført et forsøk for å studere hvordan indiseringen av skann i OIM Data Collection 5.32 påvirkes av hvilke faser som er valgt. Og disse viser at sammenhengen mellom CI og sannsynligheten for at et punkt er korrekt indisert i stor grad kan være avhengig av materialet som studeres.
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Oliveira, Janaina da Costa Pereira Torres de. "Evolução da microestrutura e da textura durante a laminação a frio e a recristalização de alumínio com diferentes níveis de pureza." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-29062009-161502/.
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O presente trabalho teve como objetivo principal estudar a evolução da microestrutura e da textura cristalográfica de três alumínios de pureza comercial com diferentes níveis de pureza, AA1100 (99,00%), AA1050 (99,50%) e AA1070 (99,70%), e do alumínio super puro, AA1199 (99,995%). A obtenção das placas de alumínio de pureza comercial foi feita pelo processo Direct Chill (DC) seguido de homogeneização e laminação a quente até a espessura final de 10 mm e o alumínio super puro foi produzido em laboratório e encontrava-se na forma de blocos fundidos. Foram utilizadas várias técnicas de análise microestrutural: microscopia óptica convencional, microscopia óptica com luz polarizada, microscopia eletrônica de varredura, microscopia eletrônica de transmissão, medidas de condutividade elétrica e dureza Vickers. Já a evolução da textura do material foi analisada pela técnica de difração de raios X, nos alumínios de pureza comercial e pela técnica de difração de elétrons retroespalhados (EBSD), no alumínio super puro. No estado como recebido e recozido a 400 ºC por 1 e 24 horas foi possível observar que nos alumínios de pureza comercial produzidos pelo processo DC não há variações na composição química ao longo da espessura. Os precipitados nos alumínios AA1100 e AA1070, no estado como recebido estavam distribuídos na direção de laminação, porém com vários locais de aglomeração dos mesmos, e no alumínio AA1050 os mesmos estavam finamente dispersos na direção de laminação. Após recozimento a 400 ºC por 1 e 24 horas as mesmas características foram mantidas, porém ocorreu um aumento na fração volumétrica do estado como recebido para os recozidos a 400 ºC, ou seja, ocorreu precipitação durante o recozimento. Quanto a análise da textura dos alumínios de pureza comercial, na superfície encontrou-se a textura de cisalhamento, devido ao esforço mecânico entre o cilindro de laminação e as amostras, tanto no estado como recebido como após os recozimentos. A ¼ da espessura e no centro do material após recozimentos ainda observou-se a textura de cisalhamento, mas também as texturas tipo cubo, cubo rodado e latão. No centro do material permaneceram a textura tipo cubo e latão. Já o alumínio AA1199 possui uma estrutura grosseira (grãos oligocristalinos), sem a ocorrência de precipitados e não foi possível obter resultados nas análises de textura, devido ao tamanho de grão grande. Após a laminação a frio com aproximadamente 70% de redução em espessura, seguido de tratamentos isócronos no tempo de 1 hora e nas temperaturas de 50, 100, 150, 200, 250, 300, 350, 400 e 500 ºC, o alumínio AA1199 apresentou uma menor temperatura para completa recristalização, em torno de 280 ºC, seguido do alumínio AA1050 (375 ºC) e dos alumínios AA1100 e AA1070 (ambos, 400 ºC). Como as composições químicas das soluções sólidas matrizes são praticamente idênticas, a variação na temperatura de recristalização deve ser atribuída aos precipitados presentes no alumínio que quando finamente dispersos na matriz impedem o movimento dos subcontornos, retardando o início da recristalização. O alumínio AA1199 possui uma temperatura para completa recristalização, menor, em relação aos outros alumínios, uma vez que não possui precipitados em sua microestrutura. Quanto a textura, na superfície e a ¼ da espessura, os alumínios de pureza comercial laminados a frio sem tratamento térmico, permaneceram com a textura de cisalhamento encontrada na superfície no estado como recebido com o surgimento da textura S. Após o tratamento térmico a 250 ºC por 1 hora apareceu a textura Goss e a 350 ºC por 1 hora a textura tipo cubo, cubo rodado e cubo ND, lembrando que em ambos os casos a textura de cisalhamento e S permaneceram. Com o auxílio da utilização da técnica de difração de elétrons retroespalhados (EBSD) encontrou-se no alumínio AA1199, a textura tipo cubo, tanto laminado a frio sem tratamento térmico quanto após os tratamentos. Após a laminação a frio com aproximadamente 80% de redução em espessura, seguida de tratamentos isotérmicos, nas temperaturas de 150, 250 e 350 ºC e nos tempos de ½, 1, 2, 3 e 4 horas, os alumínios de pureza comercial apresentaram uma temperatura para completa recristalização em torno de 350 ºC e por meio da técnica de microscopia eletrônica de transmissão observou-se arranjos celulares de discordâncias, mas não foram detectadas diferenças significativas entre esses arranjos apresentados pelos três alumínios. Diferenças certamente existem, mas para serem caracterizadas é necessário um estudo detalhado com microscopia eletrônica de transmissão. A presença de partículas de compostos intermetálicos foi observada em todas as amostras analisadas, essas partículas são resultado da baixa solubilidade do ferro e do silício no alumínio e se formaram durante as diversas etapas do processamento dos materiais.The present work had as main objective to study the evolution of the microstructure and crystallographic texture of three commercial purity aluminums with different levels of purity, AA1100 (99.00%), AA1050 (99.50%) and AA1070 (99.70%), and of the super pure aluminum, AA1199 (99.995%). The plates of commercial purity aluminum were obtained through direct chill (DC) process followed by homogenization and hot rolling until the final thickness of 10 mm. The super pure aluminum was produced in laboratory and was in the ascast condition. Several techniques of microstructural analysis were used: conventional optical microscopy, optical microscopy using polarized light, scanning electron microscopy, transmission electron microscopy, measurements of electrical conductivity and Vickers hardness. The evolution of the texture of the commercial purity aluminum was analyzed by Xray diffraction and the super pure aluminum was analyzed using electron backscatter diffraction. Variations in the chemical composition along thickness in the commercial purity aluminum produced by the DC process in the as-received condition and after annealing at 400 ºC for 1 and 24 hours were possible to observe. The precipitates in the aluminum AA1100 and AA1070, in the as-received condition were distributed in the rolling direction, including several sites of clusters of the same precipitates. In the aluminum AA1050 the precipitates were finely dispersed in the rolling direction. After annealing at 400 ºC for 1 and 24 hours the precipitate characteristics were maintained, and there was an increase in the volumetric fraction of the as-received condition in comparison to samples annealed at 400 ºC, showing that precipitation occurred during annealing. The shear texture was observed in the commercial purity aluminums, either in the as-received condition or after annealing, and this effect was due to the mechanical effort between the rolling mill and the samples. At ¼ of the thickness and in the center of the material after annealing the shear texture was still observed, and also the type cube, rotated cube and brass textures. The center of the material continues showing the type cube and brass textures. On the other hand, the aluminum AA1199 has a coarse structure (oligocrystalline grains), without the occurrence of precipitates, and texture results were not obtained due to the fact the grains are much coarser, due to the size of big grain. After cold rolling with approximately 70% of reduction in thickness, followed by isochronous treatments for 1 hour at temperatures of 50, 100, 150, 200, 250, 300, 350, 400 and 500 ºC, the aluminum AA1199 presented a smaller temperature for complete recrystallization, around 280 ºC, followed by the aluminum AA1050 (375 ºC) and of the aluminum AA1100 and AA1070 (both, 400 ºC). As the chemical compositions of the solid solutions matrixes are almost identical, the variation in the recrystallization temperature should be attributed to the presence of precipitates in the aluminum, and when finely dispersed in the matrix they impede the movement of the sub-boundary, delaying the beginning of the recrystallization. In comparison to the other aluminums, the aluminum AA1199 has a smaller temperature for complete recrystallization, since there are not precipitates in its microstructure. Observing the texture, in the surface and the ¼ of the thickness, the commercial purity aluminums, after cold rolling and without heat treatment, showed the shear texture found in the surface in the as-received condition with the appearance of the S texture. After heat treatment at 250 ºC for 1 hour the Goss texture appeared and at 350 ºC for 1 hour the type cube, rotated cube and cube ND textures; notice that in both cases the shear and S texture were still present. Energy dispersive X-ray spectroscopy (microanalysis) showed in the aluminum AA1199, the texture type cube, so cold rolled without heat treatment as after the treatments. After cold rolling with approximately 80% of reduction in thickness, followed by isothermal treatments, at temperatures of 150, 250 and 350 ºC and times of ½, 1, 2, 3 and 4 hours, the commercial purity aluminum presented a temperature for complete recrystallization around 350 ºC. Transmission electron microscopy technique showed dislocations cellular arrangements, but significant differences were not detected among those arrangements presented by the three aluminums. Differences certainly exist, but for their characterization detailed study with transmission electron microscopy is necessary. The presence of particles of intermetallic compounds were observed in all analyzed samples, those particles resulted of the low solubility of iron and silicon in the aluminum and were formed during the several stages of the processing of the materials.
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Monlevade, Eduardo Franco de. "Relações de orientação resultantes da precipitação de austenita em ferrita em aço inoxidável dúplex." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-29072003-144316/.
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Aços inoxidáveis dúplex apresentam uma estrutura composta por ferrita e austenita. O fato de a austenita ser estável à temperatura ambiente possibilita que esses aços sejam usados no estudo da reação de formação da austenita a partir da ferrita, podendo os resultados ser aplicados a aços de baixa liga, em que a austenita se transforma em martensita no resfriamento brusco, e a outros sistemas com transformações entre fases cúbicas de corpo centrado (CCC) e cúbicas de face centrada (CFC). Foram realizados estudos em um aço inoxidável dúplex do tipo DIN W.Nr. 1.4462 (UNS 31803). As amostras foram solubilizadas no campo ferrítico a 1325°C e resfriadas em água. As amostras foram ainda tratadas isotermicamente em temperaturas entre 700°C e 1100°C por tempos entre 5.000 e 30.000 segundos. Deste modo, a formação de austenita a partir da ferrita foi estudada em seu estágio inicial e em estágios avançados da reação, com relação aos seus aspectos morfológicos e cristalográficos. As morfologias encontradas apresentaram variações dependentes dos segmentos de contorno de grão em que as partículas se formam. As partículas nucleadas nos contornos de grão podem ser adequadamente descritas pela classificação morfológica de Dubé. Além disso, essas partículas apresentaram, em geral, relações de orientação do tipo Kurdjumov-Sachs e Nishyiama-Wassermann com pelo menos um dos dois grãos, podendo ser encontradas relações intermediárias entre essas duas. . Em alguns casos, as partículas mantêm relações de orientação com os dois grãos adjacentes, apresentando pequenos desvios das relações exatas relatadas na literatura. As partículas de austenita intragranulares apresentam desvios em relação à relações exatas maiores do que os encontrados nas partículas de contornos de grão. Em alguns casos, as partículas intragranulares aparentam não apresentar relações de orientação com a matriz ferrítica.Duplex Stainless Steels have a structure composed by ferrite and austenite. The fact that austenite, in these steels, is stable at low temperatures, allows the use of these steels in studies of austenite formation from ferrite, in such way that the results can be applied to low alloy steels, in which austenite transforms to martensite upon rapid cooling, and to other systems containing transformations between body-centred cubic (BCC) and face-centred cubic (FCC) phases. Studies were performed on a DIN W.Nr. 1.4462 (UNS 31803) duplex stainless steel. The samples were solution treated in the ferrite region at 1325°C and water cooled. Samples were then submitted to isothermal treatments at temperatures between 700°C and 1100°C for up to 30.000 seconds. In this way, austenite formation from ferrite was studied on initial and advanced stages of the reaction, concerning morphological and crystallographic aspects. The morphologies observed varied with the grain boundary segment in which the particles were formed. The grain boundary particles may be adequately described by the Dubé classification. Moreover, these particles presented Kurdjumov-Sachs and Nishyiama-Wassermann orientation relationships with at least one of the adjacent grains, with possibilities of occurrence of intermediate relationships between K-S and N-W relationships. In some cases, the particles show orientation relationships with both adjacent grains, with small deviations form the exact relationships reported in literature. Intragranular austenite particles show higher deviations from the exact relationships than grain boundary particles. In some cases, intragranular particles have no apparent orientation relationships with the ferrite matrix.
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Galand, Romain. "Caractérisation physique de la microstructure des interconnexions avancées Cu/Low-k pour l'étude des défaillances par électromigration." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00669388.
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L'electromigration est identifiée comme la principale cause de dégradation des interconnexions en cuivre limitant ainsi la fiabilité des produits issus de la microélectronique. Dans ces travaux nous proposons d'approfondir notre connaissance de ce phénomène en étudiant le lien qu'il présente avec les paramètres morphologiques du cuivre. Dans ce but, la technique de diffraction des électrons rétrodiffusés est utilisée. Nous avons d'abord développé les méthodes de préparation et d'acquisition nécessaires afin de pouvoir caractériser les structures issues des technologies 45 nm et au-delà que nous avons choisies pour cette étude. Un lien entre les joints de grains de forte désorientation et la localisation des cavités a alors pu être mis en évidence. Nous avons ensuite tenté de modifier la microstructure du cuivre pour impacter la fiabilité sans succès. Finalement, c'est l'intégration de nouveaux matériaux (Al, Co) renforçant l'interface supérieure, chemin de diffusion du phénomène, qui semble être la voie à adopter pour améliorer la résistance des lignes à l'électromigration.
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Verchere, Lena. "Interactions microstructure - mécanique - électrochimie locale : application à l'alliage base nickel A600." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0239.
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La corrosion sous contrainte (CSC) est un phénomène de dégradation localisée découlant de la synergie entre des paramètres microstructuraux, mécaniques et environnementaux. La compréhension des interactions entre ces paramètres permet aux industriels d’améliorer de plus en plus les modèles de fiabilité des pièces et ainsi d’augmenter la sûreté des installations. Cette étude porte sur l’Alliage 600, alliage à base nickel utilisé dans les réacteurs à eau pressurisée et sujet à la CSC.Comprendre et modéliser les interactions matériau-mécanique-environnement nécessite de se placer à l’échelle des hétérogénéités microstructurales, de champs mécaniques et de propriétés électrochimiques, afin de s’affranchir des effets de moyennation. Au cours de la thèse, ce changement d’échelle a été atteint grâce à l’utilisation de techniques locales à la fois expérimentales et numériques.Le microscope électrochimique à balayage (SECM) a permis de réaliser des mesures de courant à l’échelle des grains. En le couplant avec l’EBSD, l’effet de l’orientation cristallographique des grains sur les propriétés électrochimiques du film passif a pu être quantifié. L’effet de la nature des joints de grains a également été investigué. Par la suite, les mêmes mesures ont été faites sur une éprouvette sous sollicitation mécanique, grâce au développement d’un montage expérimental de traction in situ couplé au SECM. La microstructure obtenue par EBSD a alors été utilisée pour reconstruire une microstructure virtuelle, sur laquelle les champs mécaniques locaux ont été déterminés par un calcul en plasticité cristalline. L’influence d’un pré-écrouissage puis l’influence d’une sollicitation mécanique en traction sur la réactivité de la surface ont été montrées à l’échelle de la microstructure, confirmant que les modèles de CSC doivent intégrer les hétérogénéités localesStress corrosion cracking (SCC) is a local damaging phenomenon, which results from the synergy of microstructural, mechanical and environmental parameters. Understanding the interactions between those parameters allows manufacturers to continuously improve their reliability models for components and thus to improve facility safety. The present study focuses on Alloy 600, a nickel-based alloy which is used in pressurized water reactors and subject to SCC.Understanding and modelling interactions between the material, mechanics and environment requires decreasing the scale down to heterogeneities of the microstructure, mechanical fields and electrochemical properties, in order to avoid averaging effects. In this study, this scaling was achieved thanks to the use of experimental and numerical local techniques.A scanning electrochemical microscope (SECM) made it possible to measure currents at the grain scale. The effect of grain crystallographic orientation on the electrochemical properties of the passive film was quantified by means of a coupling of SECM with EBSD. The effect of the grain boundary type was also investigated. Thereafter, same measurements were conducted on a specimen under mechanical load thanks to the development of an experimental set-up composed of an in situ tensile machine coupled to SECM. The microstructure which was obtained by EBSD was then used to recreate a virtual microstructure on which local mechanical fields were determined through a crystal plasticity computation. The influence of cold-work and that of a tensile load on surface reactivity were then demonstrated at the microstructural scale, attesting that SCC models must integrate local heterogeneities
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Jones, Franziska Anna. "The Effect of a High-Temperature High-Pressure Nitrogen Environment with Carbonaceous Impurities on the Performance of Three Austenitic Alloys." Thesis, University of Canterbury. Mechanical Engineering, 2007. http://hdl.handle.net/10092/3268.
Full textAbstract:
WhisperGenTM heater head components are currently machined from the austenitic stainless steel Sandvik 253MA. The inner surface of the heater heads is subjected to the working gas of the engine, which is a high-pressure, high-temperature nitrogen-based environment with carbonaceous impurities. As a result of this exposure, a scale forms during operation and eventually spalls. This spalled scale causes abrasive damage to piston seals and guides, which leads to pressure loss and eventual failure of the engine. The aim of the present work was to compare the performance of the austenitic alloy 253MA with two alternative alloys, Incoloy 800H and AISI 310, thereby enabling a material recommendation. A literature review provided information about many general aspects of high temperature corrosion in similar alloys. However, little was found about the application of these alloys in environments similar to those experienced by a WhisperGenTM heater head. Therefore, laboratory experiments were conducted to indicate the relative performance characteristics of the three potential alloys (253MA, Incoloy 800H and AISI 310). To overcome the difficulties with testing at high temperatures and pressures, Thermo-Calc™ was used to calculate gas mixtures at 1 bar that approximated the chemical potentials of carbon and nitrogen in the working gas at 24 bar. Comparisons of the different materials were made via weight loss/gain measurements and metallographic analysis, which included optical microscopy, scanning electron microscopy, X-ray mapping and electron back scatter diffraction (EBSD). The laboratory test sample results were also compared with results from heater heads of the same materials that were run in an actual WhisperGenTM engine. The experimental results taken in total indicate that 253MA is the least suitable alloy for the heater head application because it exhibited poor spalling performance, internal oxidation and formation of a large amount of Cr23C6. AISI 310 was shown in all cases to develop the detrimental sigma phase, although this alloy was the least susceptible to internal oxidation. Incoloy 800H was the most resistant alloy to all forms of degradation and is thus recommended for the heater head application.
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Sidhu, Mandeep Singh. "Liquid Aluminium Corrosion Characteristics of Cast Iron and Steel." Thesis, University of Canterbury. Mechanical Engineering, 2012. http://hdl.handle.net/10092/7013.
Full textAbstract:
Cast iron and steel alloys are commonly used for tooling and structural components in Al production, Al die-casting and the aluminizing industry due to their favourable properties including high strength, good formability and low cost. However, the iquid Al corrosion of these materials is one of the crucial concerns in maintaining the efficient production. Al is produced by the electrolytic smelting of alumina. Cast iron and/or cast steel pipes - commonly known as „tapping pipes‟ - are used to extract the liquid Al produced by smelting. Tapping pipes mainly degrade by material loss because liquid Al reacts with nearly all metals. Failure of tapping pipes is a significant contributor to the maintenance expenses; therefore, the primary aim of this research is to develop a material to enhance the life time of tapping pipes. Various test methods were developed in order to examine the effect of molten Al
environment on cast iron and steel alloys. The corrosion resistance of these alloys was determined under different conditions of Al flow and temperature. The intermetallic compounds formed by exposing the ferrous to liquid Al were characterized using the Energy Dispersive X-ray Spectroscopy (EDS) and Electron Back Scatter Diffraction (EBSD) techniques. The formation, growth and nature of reaction products were revealed to establish a link to the liquid Al corrosion resistance. A relationship between the chemical composition and liquid Al corrosion resistance of cast irons could not established in the past. In the present work, the corrosion rate was found to depend upon the graphite morphology and fraction of each Fe-C phase of cast
iron matrix, which can be controlled by selecting the chemical composition. Moreover, present research suggested the guidelines for producing a cast iron with enhanced liquid
Al corrosion resistance. The presence of C-rich phases, graphite flakes and cementite was found to be effective in enhancing the liquid Al corrosion resistance of gray cast
irons. Conversely, a higher Si content was found to enhance the susceptibility of cast irons to liquid Al corrosion.
The corrosion mechanisms for ferrous alloys in liquid Al are not fully understood. Thus the subsequent analysis of the dissolution data was supported by investigating the
reaction products formed between Al and substrate materials. In addition to commonly existent ε-Fe2Al5 and ζ-FeAl3 phases, the formation of Al4C3 and κ-Fe3AlC compounds was confirmed for the first time in the intermetallic layers of ferrous alloys. The Fe3Si phase in the intermetallic layers of high Si cast irons was found, which was believed to facilitate the high corrosion rates of high Si cast irons. Moreover, the mechanism by which C in Fe-substrates affects the liquid Al corrosion resistance can be better understood given the present work.
Furthermore, the analysis presented here gives an understanding of the nature, growth and dissolution of intermetallic compounds in several cast iron alloys. Higher Si
additions to cast irons played an important role in molten metal corrosion by accelerating the material loss and changing the nature of intermetallic layers. The results of this study
clearly indicated that the dissolution and the growth of intermetallic compounds are interrelated and the dissolution and/or spallation of the intermetallic layers may be the
primary mode of liquid Al corrosion of ferrous alloys.
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Schayes, Claire. "Low cycle fatigue of the Fe-3Si steel : damage mechanisms and strain localisation by EBSD." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10002/document.
Full textAbstract:
L’objectif de ce travail de thèse était d’étudier le comportement en fatigue oligocyclique de l’acier Fe-3Si utilisé pour les rotors des nouveaux alterno-démarreurs développés par Valeo. L’étude pris en compte la relation entre la réponse mécanique et la microstructure, les mécanismes de fatigue, l’évaluation de la déformation à une échelle mésoscopique et une optimisation du dimensionnement du rotor. Les essais de fatigue, menés sur des éprouvettes d’épaisseur 350μm, ont montré un durcissement cyclique du matériau et le mode de propagation de la fissure, fragile, souligne sa faible ténacité. La formation de structure de dislocations observées par Microscopie Electronique en Transmission (TEM) et par cECCI (Controlled Electron Channelling Contrast Imaging) est dépendante de la déformation et la variation de déformation totale Δεt=0.7% apparaît comme une valeur de transition. En-dessous de Δεt =0.7%, des arrangements homogènes de dislocations et un amorçage de la fissure transgranulaire sont observés. Au-dessus de Δεt =0.7%, des structures veines-canaux et murs-canaux sont observés et l'amorçage de fissure est intergranulaire. Une étude EBSD (Electron Back-Scattered Diffraction) basée sur les paramètres KAM, GROD et GOS menée sur les éprouvettes fatiguées montre un gradient de déformation dans les grains et une localisation de la déformation aux joints de grain au-dessus de Δεt =0.7%. Enfin, en prenant en compte les propriétés en fatigue de l’acier Fe-3Si dans la base de données matériaux de la modélisation par éléments finis, des légères modifications de la géométrie du rotor ont été effectuées ce qui améliore les performances électromagnétiques de la machineThe objective of the PhD work was to investigate the low cycle fatigue (LCF) behaviour of Fe-3Si steel employed for rotors of new starter-alternators developed by Valeo. The study took into account the relation between mechanical response and microstructure, the fatigue mechanisms, the assessment of strain at a mesoscopic scale and an optimisation of the rotor design. Low cycle fatigue tests performed on 350μm thick specimen pointed out a cyclic hardening of the material. The brittle crack propagation mode underlined the low toughness of the material. The formation of dislocations structures observed by Transmission Electron Microscopy (TEM) and controlled Electron Channelling Contrast Imaging (cECCI) was strain dependant. The total strain variation Δεt =0.7% appeared as a transition value. Below Δεt =0.7%, homogeneous arrangement of dislocations and transgranular crack initiation are observed. Above Δεt =0.7%, a mixture of veins-channels and wall-channels were observed inside the grains and cracking became intergranular. An Electron Back-Scattered Diffraction (EBSD) study was then performed on the specimen fatigued above Δεt=0.7% and approached with KAM, GROD and GOS parameters. It pointed out the strain gradient within grain and highlighted the strain localisation at grain boundaries. Finally, by taking into account LCF properties of the Fe-3Si steel in the material database of the finite element modelling, slight modifications of the rotor geometry have been performed which improves the electromagnetic performances of the machine
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Eriksen, Lars. "Combined EBSD-Investigations and In-situ Tensile Tests of a Direct Metal Deposited Ti6Al4V-Alloy." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22438.
Full textAbstract:
Two blocks made of Ti6Al4V material produced by Norsk Titanium Components ned Direct Metal Deposition (DMD) production technology were delivered for this investigation. The main difference between the blocks was the different waiting time implemented in the production parameters. The different waiting time implied that the material were allowed to cool to a deisred Interpass Temperature (IT). The blocks are referred to as T200 and T600 after their lowest IT of <200 degrees celsius and 500-700 degrees celsius, respectively. Sintef Manufacturing Raufoss reported elongations of 5% and 8% in the deposition-direction of the two blocks, which was lower than the 10% elongation obtained for the building-direction. The objective was to find any explanations for the impaired ductility in the deposition-direction, and why T200 have a lower elongation than T600. To reveal differences in micro- macrostructure and deformation-mechanisms between the blocks was combined EBSD+In-situ. tensile tests the main tool. Complementary studies with optical microscopy of etched in-situ specimens were also performed.The work started with an extensive macroetching of different planes relative to the deposition-direction. This revealed a 3D-image of the epitaxially growing solidification structure of columnar prior beta grains. Measurements of grain size and morphology did not indicate significant differences between the blocks. Later was EBSD selected to prior beta grain boundaries for specimens at the center of the blocks. Measurements of the thickness of primary alfa phase also indicated small differences between the blocks. From this it was concluded that the different ITs lead to small differences in solidification structure and the amount of primary alfa phase in the center of the blocks.The EBSD + in-situ tensile tests were carried out for specimens fabricated from the blocks in the deposition direction, such that investigation could be performed in the XZ-plane. The force was applied parallel to the deposition direction X. The in-situ specimens in block T200 had a slightly higher position in the block giving a finer microstructure because of faster cooling rates. The T200 specimens also contained to deposition layers in contrast to only one in T600 specimens. This made a direct comparison difficult. However, from the four in-situ specimens investigated was the following concluded: specimens from T200 deformed more homogeneously on a macroscale. Correspondingly was more activity observed at prior beta grain boundaries for T600. The more active grain boundaries in T600 may result from the different cooling rates from the peak temperature. Slower cooling rates will give smaller prior beta grains decorated with more homogeneous alfa phase along the boundaries of T600 specimens. The frequently reported detrimental mismatch between soft and hard HCP-grains in titanium alloys were also observed. However, the orientation and morphology of these grains seems to play an important role. Cracks growing along prior beta grains were always located at the side having a non-Burgers orientation relationship. The lamellar basketweave microstructure also seem quite effective to stop cracks from growing further, because of the plates having distinct orientations.This work has also uncovered the transition in microstructure between the substrate plate and first deposition layer. The microstructure develops from a very fine bimodal plate structure, through a equiaxed region with small amounts of primary alfa phase, to early stages of the columnar beta grain configuration. The first columnar beta grains are very small in size compared to higher up in the block, and they contains very small amounts of primary alfa phase. However, the basketweave microstructure develops relatively close to the substrate plate.
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Chauve, Thomas. "La recristallisation dynamique dans les matériaux anisotropes : caractérisation et modélisation dans la glace polycristalline." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI001/document.
Full textAbstract:
La glace est un matériau de structure cristallographique hexagonale ayant une anisotropie plastique très importante. La déformation est principalement accommodée par le glissement des dislocations dans le plan basal. Cette forte anisotropie du monocristal de glace conduit lors de la déformation d’un polycristal, à de fortes hétérogénéités de déformation et de contrainte. Lors de la déformation à haute température, les mécanismes de recristallisation dynamique permettent, par le développement d’une nouvelle microstructure et d’une nouvelle texture, d’augmenter la ductilité du matériau. L’objet de cette étude est de mieux caractériser les mécanismes de recristallisation et leurs liens avec les hétérogénéités de déformation afin de mieux comprendre le développement des nouvelles microstrutures et textures ainsi que leurs impacts sur le comportement du matériaux.Ce travail est basé sur des essais de type fluage dans les conditions où la recristallisation dynamique est importante (T > 0.95T f et 0.5 < σ < 1 M P a). Deux types de polycristaux sont étudiés : la glace granulaire, considérée comme un volume élémentaire représentatif, qui permet d’appréhender d’un point de vue statistique l’impact de la recristallisation sur le développement des microstructures et des textures ; et la glace colonnaire, qui permet d’étudier les différents mécanismes de germination et leurs liens avec les hétérogénéités de déformation à l’échelle inter et intra-granulaire. Les outils de caractérisation utilisés sont la mesure in situ de l’évolution du champ de déformation par corrélation d’images numériques et la caractérisation des microstructures et des textures pré- et post- déformation par mesure optique et Electron BackScatter Diffraction (EBSD).Étant donné les fortes hétérogénéités de déformation, les mécanismes de recristallisation dynamique continue et discontinue sont actifs au cours de la déformation. La formation de sous-joints de grains, la germination par gonflement (bulging), où la migration de joints de grains ont été mises en évidence. Des germes fortement désorientés par rapport aux grains parents ont également été observés. Ces observations impliquent un mécanisme de germi- nation différent de ceux mentionnés ci-dessus. De plus, les dislocations géométriquement nécessaires composants les sous-joints de grains ont été caractérisées à l’aide du tenseur de Nye extrait des mesures EBSD. Cela a permis d’observer des sous-structures de dislocations composées de dislocations c. Ces dislocations c étaient jusqu’alors très rarement observées et seulement dans des conditions très spécifiques.Une forte corrélation entre les hétérogénéités de déformation et les mécanismes de recristallisation a été mise en évidence grâce aux mesures de champs de déformation. Les mécanismes de recristallisation se concentrent dans les zones où la déformation est importante et ont tendance à réduire les hétérogénéités de déformation. De plus, ces bandes de déformation, où la recristallisation est active, sont orientées à environ ±45° et ont une dimension supérieure à la taille moyenne des grains, ce qui montre une organisation des hétérogénéités de déformation et de contrainte à grande distance.Un modèle théorique pouvant contraindre l’orientation des germes crées par la germination spontanée est proposé. Ce modèle, basé sur la relaxation de l’énergie élastique, du fait de l’anisotropie élastique du mono-cristal de glace, permettrait de favoriser les cristaux dont l’axe c est aligné avec la direction de la contrainte principale locale. Cette étude a été complétée par des expériences numériques, basées sur un modèle à champ complet et une loi de plasticité cristalline élasto-viscoplastique qui permet de reproduire les hétérogénéités de déformation et de contrainte. Ces expériences numériques ont montré que ce mécanisme de germination orienté pourrait permettre d’expliquer le développement des textures de recristallisationIce is an hexagonal material in which deformation mainly occurs by dislocation glide along the basal plane conferring a strong viscoplastic anisotropy to the single crystal. Hence, during polycrystalline ice deformation the incompatibility between grains lead to highly heterogeneous strain. During ice creep at high temperature, dynamic recrystallisation occurs, leading to the development of a new microstructure and strong recrystallisation textures.These new microstructure and texture increase the ductility of the material. The aims of this study is to investigate dynamic recrystallisation mechanisms and their links with strain heterogeneities to better understand the development of these microstructure and texture.Creep experiments are carried out in conditions where dynamic recrystallisation is important (T > 0.95T f and 0.5 < σ < 1 M P a). Two kinds of polycrystalline samples are used: granular ice, which can be considered as a representative elementary volume and enable to understand the global impact of dynamic recrystallisation mechanisms on texture and microstructure; and columnar ice which enable to better constrain the dynamic recrystallisation mechanism such as nucleation and their link with the strain heterogeneities down to the intra and inter-granular scales. Strain field evolution is measured in situ using digital images correlation and pre- and post- deformation microstructures and textures are measured using optical imaging and Electron BackScatter Diffraction (EBSD).Due to the strong strain heterogeneities, both continuous and discontinuous recrystallisation mechanisms occured. Sub-grain boundary formation, nucleation by bulging and grain boundary migration are mechanisms very active during dynamic recrystallisation in ice. On top of that, we also observed new grains with orientations highly disoriented compared to the neighbouring grains. This observation implies a nucleation mechanism different compare to the one mentioned above. Using Nye theory on EBSD measurements constrains the geometrically necessary dislocations of the sub-grain boundaries. Tilt sub-grain boundaries made of non-basal c dislocations have been observed. Only few observations of c dislocations existed so far, all of them made in very specific conditions.A strong correlation between recrystallisation mechanisms and strain field heterogeneities have been observed. Recrystallisation mechanisms lead to a decrease and spread of strain heterogeneities. The strain localise into bands of deformation oriented at around ±45° from the compression axis and with a typical length higher than the mean grain size. These bands of high deformation localise most of the dynamic recrystallisation mechanisms. This observation shows that the long range interaction of the strain and stress heterogeneities.We propose a new model which could be able to constrain the nucleus orientation for spontaneous nucleation. This model, based on the elastic energy relaxation during nucleation tanks to the elastic anisotropy of ice single crystal, should constrain the c axis to be aligned with the locale principal stress direction. To investigate the impact of such oriented nucleation mechanism on the texture development, a numerical experiment has been proposed using full field simulation with an elasto-viscoplastic law able to simulate the strain and stress fields heterogeneities. These numerical experiments show that the oriented nucleation mechanism might be able to explain the development of recrystallisation texture
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Abbasi, Kévin. "Etude de L’endommagement en fluage de cuivre par tomographie à rayons X et polissages successifs." Thesis, Saint-Etienne, EMSE, 2013. http://www.theses.fr/2013EMSE0706/document.
Full textAbstract:
Les modèles basés sur la mécanique des milieux continus prévoient généralement une déformation à la rupture plus élevée, ainsi qu'une durée de vie en fluage beaucoup plus longue que les valeurs observées expérimentalement. Cette thèse met en évidence deux aspects de cette problématique en analysant l’endommagement à l'aide de tomographie in situ à rayons X de synchrotron et reconstruction 3D de la structure polycristalline par polissages successifs.L’endommagement en termes de fraction surfacique des cavités a été identifié dans les couches de reconstructions tomographiques perpendiculairement à l’axe de déformation. L'évolution de la fraction surfacique des cavités a été comparée avec le modèle de prédiction de Cocks et Ashby. Ce dernier surestime la durée de vie en fluage et sous-estime l’état de l’endommagement. L'importance de l'hétérogénéité initiale de l’endommagement et l’effet de localisation de l’endommagement est également souligné. L'amplitude de la plus grande fluctuation surfacique augmente de façon parabolique en fonction de la fraction surfacique moyenne.Une méthode de sectionnement sériel améliorée basée sur la profilométrie de surface a été développée. Elle permet la mesure précise de l'épaisseur du matériau enlevée localement. Les analyses ont montré que l'emplacement des cavités par rapport aux joints de grains et l’orientation cristallographique des grains au voisinage est similaire pour les échantillons déformé par différents mécanismes de fluage. La population relative des cavités de fluage présente aux joints de grains simples est supérieure à celle présente aux joints triples. Les cavités trouvées aux joints triples, cependant, sont plus grandesPower law creep damage is one of the most intriguing unsolved phenomena of materials science. Models based on continuum mechanics generally predict a much higher strain to failure, as well as a much longer creep lifetime than experimentally observed values. This thesis highlights two aspects of this problematic by analyzing creep damage in copper using in situ synchrotron tomography and 3D reconstruction of the damaged polycrystal structure by serial sectioning.Damage in terms of the area fraction of voids was first identified in slices of tomographic reconstructions of creep deformed copper. The local and global evolution of cavities area fraction was checked against the Cocks and Ashby model and it was found that the model overestimates creep lifetime and underestimates damage development. The importance of the initial damage heterogeneity and the role of damage localization are also emphasized. It was found that the amplitude of the largest damage fluctuation increases parabolically as a function of cavity’s mean area fraction.An improved serial sectioning method based on surface profilometry was developed, which allows the accurate measurement of the removed local material thickness. The 3D reconstructions enabled identifying the creep voids and the grains of the polycrystal. It was shown that with the exception of the void shape, the relationship between void location at a given grain boundary and crystallographic orientation of the neighbor grains is similar in samples deformed by different creep mechanisms. The relative population of creep voids is higher at simple grain boundaries than at triple junctions. Voids found at a triple boundary, however, are larger
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Ionescu-Gabor, Sorin. "Study and empirical modelling of recrystallisation annealing of martensitic chromium steel strip by means of EBSD." Licentiate thesis, KTH, Materials Science and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10539.
Full textAbstract:
Recrystallisation annealing, a repeated heat treatment between different stages of cold rolling of martensitic chromium steel strip, is successful when neither high rolling forces nor wear of the working rolls occur during the subsequent cold rolling. Mechanical properties as tensile strength, yield, elongation or hardness have been, by tradition, the criteria that described the quality of the annealing process. In recent years, the development of the measurement equipment in the rolling mills and of the instruments for material investigations has accentuated more and more the role played by the microstructural properties in the evaluation of the heat treatment. Two microstructural characteristics of the degree of annealing are, firstly and most important, the recrystallisation degree, and, secondly, the secondary carbide density.
The sample manufacturing and heat treatment, modelling and microstructure investigations by light optical- (LOM) and scanning electron microscopy (SEM) described in this article were carried out at Sandvik Materials Technology’s R&D Department and Bell Furnace Line in Sandviken, Sweden, while microstructure investigations and evaluation by scanning electron microscopy with field emission gun (FEG-SEM) and electron back scatter diffraction (EBSD) were done at the Corrosion and Metals Research Institute (KIMAB) in Stockholm, Sweden.
The first part of this work shows that, in contrast to the traditional methods LOM and SEM, that use chemical etching for the preparation of the samples, EBSD can successfully characterise recrystallised structures in annealed martensitic chromium steels. Unlike conventional microscopy with LOM and SEM, EBSD is able to reveal the grain geometry, as well as to separate and identify the different phases in this kind of steels (ferrite, M23-, M6-carbides). Important parameters such as grain size, particle size and recrystallised fraction can be measured with high accuracy. This information can be used to understand, evaluate, control and even predict the recrystallisation annealing of martensitic chromium steel.
The second part of this work presents how the results from microstructure description by EBSD can be directly used in relatively simple empirical models for determination of recrystallisation degree as function of the annealing parameters and the deformation history. EBSD was applied to evaluate the degree of recrystallisation in a series of annealing tests, with the purpose to model recrystallisation temperature in two types of martensitic chromium steel strip, a traditional one and one alloyed with molybdenum, cold rolled with different amounts of reduction and annealed with different temperatures, soaking times and heating rates. The empirical quadratic models were built with Umetrics’ software for experimental design, MODDEÒ 8.0 and they defined the recrystallisation degree (limits for LAGB and HAGB were set to 1.5° and 7.5° for the first grade and 2.5° and 10° for second one) and the secondary carbides density as functions of annealing temperature, soaking time and cold reduction (the factor heating rate was removed as nonsignificant). To be observed that these empirical models were fit much better for the recrystallisation degree than for the secondary carbides density.
The modelling work described above, together with the implementation of online physical temperature models in the bell annealers may lead to an increased productivity in the production plant by shortening the annealing cycle and minimising scrap and thus to an economical gain of ca 1,5 MSEK per year at Sandvik Materials Technology.
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Thieme, Manuel. "Résistance visqueuse et frictionnelle du manteau lithosphérique : caractérisation microstructurale de l'olivine polycristalline déformée expérimentalement." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG061/document.
Full textAbstract:
La convection dans le manteau terrestre est la principale force motrice du mouvement des plaques tectoniques. Alors que les parties inférieures du manteau supérieur se déforment de manière ductile, les plaques tectoniques sont rhéologiquement plus rigides que l'asthénosphère sous-jacente. Pour comprendre le couplage entre la convection profonde et les plaques tectoniques à la surface de la Terre, il est essentiel de comprendre les mécanismes de déformation visqueuse et frictionnelle du manteau lithosphérique. Mais à ce jour, la rhéologie du manteau supérieur juste au-dessous de la discontinuité de Mohorovicic est encore mal comprise. De plus, les premiers stades de la déformation viscoplastique à des températures intermédiaires (600-1000 ° C) pertinentes pour le manteau lithosphérique, ne sont ni bien documentés ni quantifiés. Dans le passé, la plupart des expériences de déformation étaient effectuées à des températures très élevées (> 1200 ° C). Pour fournir des valeurs mécaniques précises pour le manteau lithosphérique, nous avons besoin de données mécaniques mais aussi de la caractérisation de la microstructure associée pour comprendre la physique des mécanismes en jeu lors de la déformation permanente des roches riches en olivine. Dans cette thèse, nous avons réalisé des expériences de déformation en compression axiale à l'aide d'une presse Paterson (Géosciences Montpellier, Université de Montpellier, France) à haute pression et température (300 MPa, 1000-12000 ° C) et en torsion (‘rotary shear frictional testing machine’ au laboratoire de mécanique des roches, université de Durham, Royaume-Uni) à pression et température ambiantes. Les échantillons ont été caractérisés par microscopie électronique à balayage, diffraction d’ d'électrons rétrodiffusés et microscopie électronique en transmission. Après un chapitre d'introduction où l'état de l'art est détaillé et un chapitre consacré aux méthodes expérimentales et analytiques utilisées dans les projets scientifiques, la thèse s'organise en trois chapitres, chacun correspondant à trois articles scientifiques: le premier est publié (1) Évolution de la contrainte et des microstructures associées au fluage transitoire de l'olivine à 1000-1200 °C (Phys. Earth Planet. Int., doi: 10.1016/ j.pepi.2018.03.002. (https: //hal.archives- ouvertes.fr/hal-01746122) et les deux autres sont en préparation, (2) Densité de disclinaisons dans l'olivine polycristalline déformée expérimentalement à 1000 ° C et 1200 ° C (3) Déformation par cisaillement de l'olivine nano- et micro-cristalline. Le premier projet du chapitre III a montré que le durcissement mécanique observé ne peut pas provenir d'une simple augmentation de la densité de dislocations (e.g., la forêt) et que d'autres mécanismes doivent être mis en œuvre pour compenser les limites de glissements des dislocations. Dans le chapitre IV, les densités de dislocation géométriquement nécessaires (GND, défauts de translation) et les disclinaisons (défauts de rotation) sont quantifiées sur une série de roches déformées à différentes températures, déformations finies et niveaux de contrainte, mais aucune corrélation n'a été identifiée entre la densité de disclinaisons, et la contrainte, la déformation finie, ou la densité de GND. Le rôle des disclinaisons serait donc limité à la migration aux joints de grains, ce qui peut être suffisant pour débloquer les dislocations dans l'agrégat d'olivine polycristalline. Au chapitre V, les expériences de torsion ont confirmé l'effet négligeable de la taille du grain (olivine de 0,7 à 70 µm) sur la diminution drastique du coefficient de frottement, mais la caractérisation des échantillons n’a pas permis d'élucider le mécanisme principal de déformation. Cette thèse a permis de mieux caractériser la transition fragile-ductile d'une roche de type dunite à grains fins soumise à une déformation permanente aux températures du manteau sommitaleConvection in Earth’s mantle is the major driving force behind the movement of tectonic plates. While the lower parts of the upper mantle deform in a ductile way, the plates themselves are rheologically more rigid than the asthenosphere beneath. To understand how convection yields tectonic plates, it is vital to quantify the viscous and frictional strength of the lithospheric mantle. Yet to date, the rheology of the uppermost mantle just below the Mohorovicic discontinuity is still poorly understood. Furthermore, the early stages of visco-plastic deformation at intermediate temperatures (600 – 1000 °C) relevant of the lithospheric mantle are not well documented or quantified. In the past, most deformation experiments were performed at high temperatures (> 1200 °C). To provide accurate mechanical values for the lithospheric mantle, we need mechanical data but also a characterization of the associated microstructure to understand the deformation mechanisms at play during permanent deformation of olivine-rich rocks. In this thesis, I have performed deformation experiments in axial compression using a Paterson press (at Géosciences Montpellier, University of Montpellier, France) at high pressure and temperature (300 MPa, 1000 -12000 °C) and in torsion using a low to high velocity rotary shear frictional testing machine (Rock Mechanics Laboratory, Durham University, UK) at room pressure and temperatures. The recovered samples were characterized using scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. After an introduction chapter where the state-of-the-art is detailed, and a chapter focusing on experimental and analytical methods used during scientific projects, the thesis is organized as three subsequent chapters, each of them corresponding to three scientific articles: one is published (1) Stress evolution and associated microstructure during transient creep of olivine at 1000-1200 °C (Phys. Earth Planet. Int., doi: 10.1016/j.pepi.2018.03.002.); and the two others are in preparation, (2) Disclination density in polycrystalline olivine experimentally deformed at 1000 °C and 1200 °C; and (3) Shear deformation of nano- and micro-crystalline olivine at seismic slip rates. Chapter III has shown that the observed mechanical hardening can not come from a simple increase in dislocation density (e.g., entanglement) and that other mechanisms must be at play to compensate for the limitations of dislocation slip. For the first time, in chapter IV the densities of geometrically necessary dislocations (GND, translational defects) and disclinations (rotational defects) are quantified on a series of rocks deformed at different temperatures, finite strains and stress levels. No correlation has been identified between disclination density and stress, strain or GND. The role of the disclinations will therefore be limited to migration at grain boundaries, which may be sufficient to unblock dislocations in the polycrystalline olivine aggregate. In chapter V, torsion experiments confirmed the negligible effect of grain size (olivine from 0.07 to 70 μm) on the drastic decrease of the coefficient of friction, but the characterization of the samples did permit to shed light on the main mechanism of deformation. Thanks to an experimental approach and up-to-date material characterization, this thesis permitted better characterization of the brittle-ductile transition of a fine-grained dunite-type rock subjected to permanent deformation at uppermost mantle temperatures
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Cunnett, Glinys. "Children with EBSD and staff working together to create an environment supportive of dealing with anger." Thesis, Open University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435920.
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Mateescu, Nora-Maria Materials Science & Engineering Faculty of Science UNSW. "Development of 3D-EBSD and its application to the study of various deformation and annealing phenomena." Publisher:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41541.
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The ability to generate three dimensional (3D) microstructures in solids is of great importance in understanding their true nature, as it eliminates speculation about the spatial distribution of features associated with conventional two dimensional (2D) imaging techniques. There are several recently-developed 3D techniques for determining the spatial distribution of microstructural features, each with a given resolution. There is considerable interest in the development of a specific serial sectioning methodology, termed 3D electron backscatter diffraction (3D-EBSD), which combines a focused ion beam (FIB) with EBSD interfaced to a field emission gun scanning electron microscope. Here, FIB is used as a serial sectioning device for cutting parallel slices of single- and multi-phase materials with a site-specific accuracy of up to 50 nm. Each consecutive slice is mapped by EBSD and the complete dataset combined using advanced computer algorithms to generate a volume of a material whereby the true crystallographic features can be analyzed at submicron resolution. The aims of the thesis was to develop 3D-EBSD into a powerful materials analysis tool and use it to resolve several issues concerning the nature of the deformed state and the nucleation and the growth behaviour of recrystallizing grains. The study commenced with an investigation into the effect of material type (restricted to face centred cubic AI, Cu and Au metallic crystals), FIB milling conditions and EBSD software variables on the quality of EBSD patterns generated on ion-milled surfaces of these materials. The effect of material type on EBSD pattern quality following FIB milling was found to be significant with relatively poor quality EBSD patterns obtained for metals of low atomic number. It was demonstrated, particularly for the high atomic number metals, that moderate FIB milling currents (~1-5nA) generated good quality EBSD maps from a given ion-milled surface. This preliminary work was necessary for balancing the time required for serial sectioning during 3D-EBSD and the generation of sufficient quality EBSD maps from each ion-milled surface. The outcomes of this investigation were applied to two major 3D-EBSD investigations on the microstructural and crystallographic characteristics of: (i) deformation features generated in a cold rolled interstitial free (IF) steel, with particular emphasis on the formation of microbands; and (ii) recrystallization of a cold rolled nickel alloy containing coarse (>1 ??m) silica particles, with particular attention given to the generation of particle deformation zones and their influence on nucleation and growth of recrystallizing grains including particle stimulated nucleation (PSN), twin formation during PSN and the growth behaviour of various types of grain boundary into the deformation microstructure. The foregoing 3D-EBSD studies were significant as they revealed various microstructural and crystallographic features not usually clearly evident in conventional 2D micrographs obtained by either EBSD or optical metallography. For example, the technique demonstrated that microbands in cold rolled IF steel consist of irregular curved surfaces that reconcile findings that microbands straight and aligned parallel to slip planes when viewed in normal direction-rolling direction sections but are wavy in transverse direction-rolling direction sections. Three slip planes were found within the angular range of the curved surface of the microband, which indicates that multiple slip planes are operative during deformation. The work also showed the influence of particle diameter on the misorientations generated within particle deformation zones and clearly showed that particle stimulated nucleation (PSN) occurred at particles greater than 1.5-2 ??m. It was observed that PSN in the nickel sample also generates contiguous grains separated by both coherent and incoherent twin boundaries and, on further growth of these grains into the matrix, the coherent boundary dominates and remains parallel to the primary growth direction of the grains.
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Sukhopar, Olga Verfasser], Günter [Akademischer Betreuer] Gottstein, and Wolfgang [Akademischer Betreuer] [Bleck. "Experimentelle und simulationsgestützte Studien der Würfelkeimbildung basierend auf EBSD Untersuchungen / Olga Sukhopar ; Günter Gottstein, Wolfgang Bleck." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130327035/34.
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Wenn, Maia. "EBSD karakterisering av et austenittisk rustfritt AISI 304 stål under in situ deformasjon ved ulike temperaturer." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25837.
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Denne masteroppgaven kartlegger martensittdannelsen i et austenittisk rustfritt stål som følge av ytre påkjenninger i form av temperatur og spenning. Dette er gjort ved hjelp av in situ deformasjon i skanning elektronmikroskop (SEM) i kombinasjon med diffraksjon av tilbakespredte elektroner (EBSD). Stålet som er undersøkt er AISI 304, som er et austenittisk rustfritt stål med en fullstendig austenittisk struktur. Stålet ble undersøkt ved tre forskjellige tilfeller•Martensittdannelse som følge av bråkjøling i flytende nitrogen•Martensittdannelse som følge av strekktesting ved romtemperatur•Martensittdannelse som følge av strekktesting ved lave temperaturerUnder in situ forsøkene ble et spesiallaget strekkbord montert i SEM, og prøvene ble strukket opp til 12 %. For strekktesting ved lave temperaturer ble en spesiallaget kaldfinger montert på prøven, og deformasjonen ble utført når temperaturen hadde stabilisert seg. Temperaturen stabiliserte seg på henholdsvis -51,7 °C og – 47 ºC. Ved bruk av in situ EBSD, er en av utordringene å finne gode nok kalibreringspunkt etter hvert som deformasjon blir introdusert i materialet. I tillegg oppstår det kontaminasjon av overflaten jo lengre skannet pågår, spesielt ved lave temperaturer. Det ble derfor utviklet en ny metode for kalibrering av skannene. Dette ble gjort for å undersøke om det er mulig å forenkle opptaksprosessen, og dermed korte ned tiden i SEM ved opptak av mange diffraksjonsmønstre av det samme området ved for eksempel strekk og kjøling. Den forenklede indiseringsmetoden går ut på at man bruker kalibreringspunktene for det første skannet ved kalibrering av alle skannene over området. Slik unngår man å ta opp nye kalibreringspunkt for hvert skann. Alle filene fra det første skannet unntatt filen med selve mønsteret gjenbrukes ved indisering av alle skannene. Det ble konkludert med at den nye indiseringsmetoden gir litt dårligere kvalitet enn den som brukes per i dag, men i tilfeller hvor man ikke finner gode kalibreringspunkt som følge av deformasjon eller kontaminasjon, vil den nye indiseringsmetoden være avgjørende for å få et resultat. Ved bråkjøling i flytende nitrogen ble det ikke observert martensittdannelse i prøvene som ble undersøkt. Det ble derimot dannet små fraksjoner av martensitt i prøver strukket ved romtemperatur og i prøver strukket ved lave temperaturer. Martensittandelen som ble dannet var større for prøver strukket ved lave temperaturer enn for prøver strukket ved romtemperatur. Det ble dannet omtrent 1 % martensitt i prøver strukket til 8 % ved romtemperatur, og 2,5 % martensitt i prøver strukket til 8 % ved lave temperaturer. Det ble konkludert med at austenitt lettere transformeres til martensitt for plastisk deformasjon ved lave temperaturer enn ved romtemperatur som følge av høyere termodynamiske drivkrefter. Etter in situ forsøkene ble en prøve som var strukket til 12 % ved romtemperatur, og en prøve som var strukket til 12 % ved lav temperatur, slipt og elektropolert før de på nytt ble undersøkt med EBSD. Det ble observert henholdsvis 0,1 % og 0,6 % martensitt i prøvene, noe som er en mindre martensittandel enn det som ble observert under selve forsøket. Prøven strukket ved lav temperatur viste også her en større martensittandel enn prøven strukket ved romtemperatur. Martensitten som ble dannet lå langs austenittkorngrenser. Ved hjelp av TSL OIM Analysis ble det bekreftet at martensitten har en K-S orienteringssammenheng med austenitten den ble dannet fra, noe som indikerer at martensitten er riktig indisert. Ved hjelp av et Schmid faktor kart i TSL OIM Analysis, ble slipstriper introdusert i mikrostrukturen undersøkt. Det teoretiske kartet anga hvilke korn det mest sannsynlig oppstod slip i, og dette ble sammenlignet med IQ kartene, hvor sliplinjene var tydelige, til samme prøve ved deformasjon. Det ble konkludert med at sliplinjer i stor grad oppstod i områder hvor Schmid faktoren var høy, det vil si områder hvor sliplinjer teoretisk mest sannsynlig oppstår, men at det er viktig å ta hensyn til andre faktorer som kan påvirke dannelse av sliplinjer, som for eksempel kornstørrelse.  
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Sukhopar, Olga [Verfasser], Günter Akademischer Betreuer] Gottstein, and Wolfgang [Akademischer Betreuer] [Bleck. "Experimentelle und simulationsgestützte Studien der Würfelkeimbildung basierend auf EBSD Untersuchungen / Olga Sukhopar ; Günter Gottstein, Wolfgang Bleck." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130327035/34.
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Rodrigues, Jean Carlos. "Estudo da textura cristalográfica em um aço de grão não orientado com 3,3% SI via EBSD"." Universidade Federal de Minas Gerais, 2011. http://hdl.handle.net/1843/BUOS-8NGN6C.
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This work consists in the analysis of the texture of samples of steel with 3.3wt% Silicon according to the variation of the final annealing temperature. The samples of this electrical steel were 2mm thick after hot rolling and were subjected to intermediate annealing at 1030°C. Then they underwent the first stage of cold rolling, having their thickness reduced to 0,6mm. After that, they underwent another annealing process at 1030°C and a second stage of cold rolling, with thickness reduction to 0,23mm. Finally, the samples were annealed at temperatures which varied from 620°C to1100°C. This thermomechanical processing was carried out at the ArcelorMittal Inox Brasil and the rolling stages were performed in a reversible Steckel. A final annealing at higher temperatures led, as expected, to an increase be the final grain size. It was verified that the fractions in the áreas of fibers e reached lower values to samples which were annealed between 1020 e 1080 °C and that, within these temperature levels, fiber reached higher temperature levels in this parameter. Finally, around a temperature of 1060°C the grain size is 110m. This grain size can be considered excellent to the scope of this study, once that at this point one can verify higher fraction of favorable orientations and lower fraction of unfavorable orientations to the magnetic properties.Este trabalho consiste na análise da textura de um aço com 3,3% de silício em função da variação da temperatura de recozimento final. As amostras desse aço elétrico saíram da laminação a quente com espessuras de 2mm, foram submetidas a um recozimento intermediário a 1030°C, depois passaram pelo primeiro estágio de laminação a frio, onde suas espessuras foram reduzidas para 0,6mm. Em seguida, experimentaram outro recozimento a 1030°C e um segundo estágio de laminação a frio com uma redução de espessura para 0,23mm. Por último, as amostras foram recozidas com temperaturas variando de 620°C até 1100°C. Este processamento termomecânico foi realizado na ArcelorMittal inox Brasil, as etapas de laminação foram executadas em um laminador reversível Steckel. Observou-se um aumento no tamanho do grão para temperaturas de recozimento finais mais altas. Verificou-se que as frações em área das fibras e atingem valores mais baixos para as amostras recozidas entre 1020 e 1080°C e que dentro dessa faixa de temperaturas a fibra atingiu valores mais elevados nesse parâmetro. Por fim, em torno da temperatura de 1060°C tem-se um tamanho de grão no valor de 110m. Este tamanho de grão pode ser considerado como ótimo para o escopo deste estudo, visto que neste ponto verifica-se maior fração das orientações favoráveis e menor fração das orientações desfavoráveis às propriedades magnéticas.
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Soulié, Camille. "Formation des chondres et relation avec leurs auréoles de matrice à grains fins." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0378/document.
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Les météorites les plus primitives, appelées chondrites, sont les témoins privilégiés de la formation des premiers solides du système solaire et des processus qui ont conduit à la naissance des premiers corps planétaires. Les chondres, qui sont des sphérules ferromagnésiennes ignées, et leur matrice finement cristallisée constituent l’essentiel du volume des chondrites primitives. L’origine des chondres comme celle de la matrice est encore largement débattue. Cette thèse interroge les relations qui existent entre les chondres et la matrice à grains fins qui les auréole fréquemment, notamment dans les chondrites carbonées. En prenant l’exemple de la chondrite Vigarano (CV3) nous explorons la piste d’un continuum des conditions physico-chimiques pour former les chondres et leurs auréoles de matrice à grain fin. La thèse aborde cette problématique par une double approche : une approche expérimentale consacrée à la quantification des vitesses de dissolution de l’olivine dans des liquides silicatés caractéristiques des chondres de type I et une approche de caractérisation détaillée de la minéralogie, des fabriques et de la composition isotopique de l’oxygène des chondres et de leurs auréoles de matrice à grains fins dans Vigarano. Ces travaux suggèrent que chondre et matrice pourraient enregistrer une continuité d’interaction avec le gaz environnant, d’abord de type liquide/gaz (solubilité) pour la formation des chondres, puis de type solide/gaz (condensation) à plus basse température pour la formation des auréoles de matrice à grains finsThe most primitive meteorites, the chondrites, are our best witnesses of solar system birth and formation of first solids as well as processes that formed the first planetary bodies. Both chondrules, which are ferromagnesian igneous spherules, and fine-grained matrix, constitute the largest volume fraction of primitive chondrites. Their origin still constitutes a matter of debate. This thesis questions the relationship between chondrules and fine-grained matrix, called fine-grained rims, that frequently overlay chondrules in primitive carbonaceous chondrites. By taking the example of Vigarano (CV3), we explore the idea that chondrules and fine-grained rims could form in a continuum of physical and chemical conditions. This thesis combines both experimental and characterization approaches, with an experimental determination of olivine dissolution rates in molten silicates representative of type I chondrule melts and a detailed petrographic characterization of mineralogy, fabrics and oxygen isotopic composition of chondrules and their fine-grained rims in Vigarano. This work suggests that chondrules and their fine-grained rims could register a continuous interaction with surrounding gas, with first, chondrule formation from liquid/gas interaction (solubility) and then fine-grained rim formation, at lower temperature and from solid/gas interaction (condensation)
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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.
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Cette thèse se concentre sur certains des derniers progrès réalisés en microscopie d'orientation (EBSD) afin d'améliorer l'analyse des microstructures complexes de l'acier et de contribuer à une meilleure compréhension de la genèse des microstructures héritées par transformation de phase. Ceci est d'une importance capitale pour optimiser les traitements thermomécaniques et les propriétés mécaniques. La première question était de capturer la formation d'austénite à haute température avant la transformation complète en ferrite/bainite ou martensite pendant le refroidissement. Dans ce but, des traitements thermiques EBSD in-situ ont été mis en œuvre dans un MEB en complément de la reconstruction cristallographique indirecte. Un module de chauffage au design optimisé pour l'EBSD a été couplé à une caméra EBSD dernière génération. Le résultat montre que des clichés de haute qualité peuvent être acquis à des températures d'environ 1000°C avec une vitesse d'indexation de plus de 1000Hz. Cela permet de capturer l'évolution dynamique de la microstructure héritée par transformation de phase et la croissance des grains d'austénite. Différents cas d'études réalisées avec différents partenaires industriels illustrent les performances de l'analyse EBSD à haute température, avec un accent particulier sur l'analyse de l'affinement du grain d'austénite dû aux traitements de trempe. La deuxième question était d'appliquer l'analyse avancée des clichés EBSD à des microstructures d'acier complexes et multiphases afin d'améliorer les données d'orientation acquises en termes de taux d'indexation et de discrimination des phases (en particulier pour les phases à symétrie cristalline cubique). Pour l'approche classique d'indexation par Transformée de Hough (HT), l'optimisation de la liste de réflecteurs par phase est la caractéristique la plus importante pour une discrimination de phase fiable. L'approche "Refined Accuracy" (RA) récemment proposée est sensible à la différence de largeur de bande de Kikuchi et s'avère capable de discriminer les phases cubiques avec une différence de paramètre de réseau de 0.73Å. Les approches Pattern Matching qui comparent les clichés expérimentaux à un dictionnaire de cliches simulés dynamiquement se sont avérées les plus performantes pour (1) indexer les clichés de mauvaise qualité souvent trouvés dans les îlots de Martensite/Austenite et (2) discriminer les phases cubiques correspondant à des inclusions ou des précipités mineurs dans une matrice de ferrite/austenite. La meilleure métrique pour comparer les clichés expérimentaux et simulés est la Normalized Cross Correlation (NCC). Enfin, la dernière question était de progresser dans la discrimination automatisée des produits de transformation (ferrite/bainite/martensite) en utilisant données de l'EBSD. Ces phases sont toutes indexées comme phase ferrite-cubique mais des paramètres comme la qualité du cliché ou le KAM, peuvent être utilisés pour les différencier. Cependant, les critères définis par l'utilisateur pour identifier ces phases sont souvent subjectifs et la procédure peut prendre beaucoup de temps. Pour ces raisons nous avons mis en place des modèles d'IA basés sur la qualité du cliché et le KAM. Une méthode d'apprentissage supervisé a été développée en utilisant l'architecture U-Net CNN pour séparer ferrite/bainite supérieure/martensite. Des précisions élevées ont été atteintes pour les microstructures ayant des caractéristiques similaires à celles montrées au modèle pendant l'entrainement, ce qui en fait une bonne option pour les tâches répétitives. Pour éviter l'étiquetage, des approches non supervisées ont également été testées. Une approche de clustering k-means a démontré une capacité relativement bonne à discriminer la bainite supérieure et inférieure en utilisant des caractéristiques extraites de la reconstruction cristallographique indirecte. D'autre part, les CNN non supervisées ont montré une excellente capacité à discriminer la ferrite [...]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
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Bernardi, Heide Heloise. "Processamento e caracterização microestrutural de nióbio deformado plasticamente por extrusão em canal angular." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/97/97134/tde-27092012-123519/.
Full textAbstract:
Amostras de nióbio de alta pureza na forma de monocristais, bicristais e policristais foram retiradas de seções longitudinais de lingotes fundidos por feixe eletrônico. As amostras foram deformadas via extrusão em canal angular (ECAE - Equal Channel Angular Extrusion) em temperatura ambiente até 8 passes, utilizando a rota Bc numa matriz com ângulo de intersecção entre os canais de = 90º. As amostras foram caracterizadas em termos da evolução microestrutural e da textura de deformação. A caracterização microestrutural foi realizada com o auxílio de microscopias ótica, eletrônica de varredura e eletrônica de transmissão, além de medidas de difração de elétrons retroespalhados (EBSD) para determinação da microtextura e da mesotextura. Medidas de microdureza Vickers foram realizadas para acompanhar o encruamento e o amolecimento das amostras. Um outro monocristal de nióbio foi deformado em 1 passe via ensaio interrompido, utilizando uma matriz com ângulo = 120º, a fim de estudar a evolução da textura durante a passagem pelo canal de ECAE. A textura foi determinada por meio de difração de raios X e comparada com os dados da literatura para materiais deformados via ECAE com estrutura CCC e também com as texturas simuladas pelo modelo VPSC (visco-plastic self-consistent). No estudo comparativo numa escala maior (monocristal e policristal), verificou-se que houve um refinamento microestrutural significativo após 8 passes. O espaçamento médio entre os contornos de alto ângulo medido perpendicular à direção de extrusão foi próximo nos dois casos (500 nm), maior que o observado para o monocristal deformado numa escala menor (440 nm). Os resultados mostram ainda que os grãos do policristal deformado são mais equiaxiais que os do monocristal. Amostras foram recozidas isotermicamente para avaliar o comportamento frente ao engrossamento microestrutural. Os resultados mostram que o engrossamento torna-se apreciável, em geral, a partir de 500oC com a ocorrência de recristalização descontínua. Acima de 700oC, o crescimento normal de grão passa a ser o principal mecanismo de engrossamento microestrutural. Efeitos de orientação importantes foram observados no bicristal nos estados encruado e recozido.High-purity niobium single crystals, bicrystals and polycrystals were cut out from longitudinal sections of ingots processed by electron beam melting. Samples were deformed by Equal Angular Channel Extrusion (ECAE) at room temperature up to 8 passes, using the route Bc with a die angle = 90o. Samples were characterized in terms of their microstructural evolution and deformation textures. Microstructural characterization was performed using optical, scanning electron, and transmission electron microscopies, as well as electron-backscatter diffraction measurements (EBSD) to determine both microtexture and mesotexture. Vickers microhardness testing was performed to follow hardening and softening behaviors in the samples. Another single crystal was deformed by 1 pass in an interrupted ECAE experiment using a die angle = 120o to follow the changes in texture through the extrusion channel. Texture was determined by X ray diffraction and compared with those reported in the literature for deformed bcc materials and also with those predicted using the viscoplastic self-consistent model (VPSC). A comparative study in a larger scale (single and polycrystals) was also performed. It was observed that there is a significant refinement of the microstructure after 8 passes. The average spacing between high angle boundaries perpendicular to extrusion direction was close in the two cases (500 nm), larger than observed in the single crystal deformed in a smaller scale (440 nm). Results also show that ultrafine grains of the deformed polycrystal are more equiaxial compared to those found in the deformed single crystal. Samples were annealed to evaluate their behavior regarding microstructural coarsening. Results show that coarsening becomes noticeable at temperatures higher than 500oC by means of discontinuous recrystallization. Above 700oC, normal grain growth becomes the main microstructure coarsening mechanism. Important orientation effects were observed in the bicrystal in both deformed and annealed states.
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Martins, Juliana de Paula. "Evolução da microestrutura e da textura durante o processamento de chapas da liga Al-Mn-Fe-Si (3003) produzidas por lingotamento contínuo: um estudo comparativo com o processo semi-contínuo." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-31012006-124433/.
Full textAbstract:
A principal motivação para o desenvolvimento do presente projeto de doutorado foi comparar as microestruturas e texturas resultantes da liga de alumínio 3003 obtida por lingotamento contínuo e semicontínuo. O processo roll caster (lingotamento contínuo em cilindros) tem sido crescentemente utilizado na indústria de laminação de alumínio. Produtos que antes sofriam altos graus de deformação durante seu processamento são hoje obtidos nas dimensões próximas da espessura final. Com o intuito de entender este processo relativamente novo, as microestruturas e as texturas (macrotextura e microtextura), ao longo da espessura, das chapas produzidas por lingotamento contínuo e por lingotamento semicontínuo (placas fundidas com 250 mm de espessura, seguido de homogeneização e laminação a quente) foram analisadas. Foi possível constatar que os materiais provenientes dos dois processos diferem bastante e que ao longo da espessura também há grandes diferenças. Foi possível observar que durante o processamento roll caster há considerável deformação plástica, com a formação de células de discordâncias e subgrãos. Foi possível observar, também, que a microestrutura, a morfologia e o tamanho de grão, da amostra caster bruta de fundição são mais homogêneos que na amostra laminada a quente. As duas chapas, a laminada a quente e a obtida por lingotamento contínuo, exibem forte gradiente de textura ao longo da espessura. A textura predominante nos dois processos, ao longo da espessura, é a do tipo latão {011}. A evolução da textura do material proveniente do processo roll caster também foi caracterizada após laminação e posterior recristalização, revelando a presença de componentes típicas de laminação e de recristalização de alumínio. Após laminação a frio com redução de 91% e posterior tratamento térmico de 400°C por 1 h, a chapa proveniente do processo caster apresentou uma textura de recristalização caracterizada pela presença da componente cubo (recristalização) somada à parcela de textura de deformação. No caso do alumínio e suas ligas, sabe-se que esta textura proporciona os melhores resultados para minimizar o efeito de orelhamento durante a estampagem. Outro ponto relevante do trabalho foi o aperfeiçoamento da técnica de extração de precipitados para a liga 3003, uma vez que, a extração de precipitados em ligas de alumínio é especialmente problemática, pois a maioria das partículas presentes dissolve-se até mais facilmente que a matriz de alumínio. Algumas técnicas foram testadas: 1. dissolução química em solução de iodo em metanol; 2. dissolução eletrolítica em solução de ácido benzóico e hidroxiquinolina em clorofórmio e metanol; 3. dissolução eletrolítica em solução de ácido perclórico, butil glicol, álcool etílico e água; 4. dissolução química em solução de fenol. A técnica que apresentou melhores resultados foi a dissolução química com fenol, onde foi possível separar os precipitados da matriz alumínio. Com o auxílio desta técnica foi possível analisar as transformações de fase do composto intermetálico Al6Mn durante tratamentos térmicos. Obtiveram-se dados da completa transformação da fase Al6Mn em alfa-AlMnSi, também conhecida na literatura como, transformação "six to alfa". A precipitação e os precipitados desempenham um papel importante na cinética de recristalização e no tamanho de grão final. Para se entender este comportamento, comparou-se uma chapa que sofreu tratamento térmico antes da laminação com outra chapa que foi laminada no estado bruto de fundição. Os resultados revelaram que a recristalização foi retardada na amostra, inicialmente, bruta de fundição. A precipitação ocorreu simultaneamente com a recristalização, com isso, os dispersóides precipitaram preferencialmente na microestrutura deformada, em subcontornos ou nas discordâncias isoladas, levando a um considerável atraso no rearranjo das discordâncias e na nucleação da recristalização.The main reason for the development of this PhD Thesis was to compare the microstructures and textures of the 3003 aluminum alloy produced from continuous and semi-continuous casting processes. The roll caster process (continuous casting) has been increasingly used in the aluminum industry. Products usually obtained by means of heavy rolling operations in the past are nowadays obtained with dimensions close to the final ones using the roll caster technology. To understand this new process, microstructures and textures (macrotexture and microtexture) along the thickness of the sheet produced by continuos casting and semi-continuous casting (plates with 250 mm thickness, followed by homogenization and hot rolling) have been investigated. It was possible to verify that materials coming from these two processes did differ each other a lot mainly across the thickness. During roll casting the plastic deformation was large enough to promote the formation of dislocation cells and subgrains. It was also possible to notice that the microstructure, morphology, and grain size from as-cast sample are more homogenous than the ones found in hot rolled samples. Both the sheets obtained by hot rolling and continuous casting have shown a strong texture gradient across the thickness. The predominant texture in both processes is the Brass component {011} . The texture evolution from sheets obtained by roll casting was also determined after rolling and subsequent recrystallization. It shows the presence of typical components of rolling and recrystallization of aluminum. After 91% cold rolling and subsequent recrystallization at 400°C for 1 h, the cube component (recrystallization texture) and the deformation texture were observed. It is well known that this texture minimizes earing effects during deep drawing of aluminum products. Another relevant point in this work was the development of the technique for the extraction of precipitates for the aluminum 3003 alloy. The extraction of precipitates extraction is particularly problematic in aluminum because most of the particles tend to dissolve more readily than the aluminum matrix. Some of the techniques performed are the following: 1. chemical dissolution with iodine in methanol solution; 2. electrolytic dissolution with benzoic acid and hydroxyquinoline in chloroform and methanol; 3. electrolytic dissolution with perchloric acid, butyl-glycol and ethanol; 4. chemical dissolution with phenol solution. Chemical dissolution with the phenol solution was the technique that provided the best results. It was possible to separate precipitates from the aluminum matrix. With this extraction technique it was possible to analyze phase transformations of the intermetallic compound Al6Mn during heat treating of this alloy. The phase transformation of the Al6Mn compound into alfa-AlMnSi, also known as 6-to-alfa transformation, could be followed in detail by means of this technique. Precipitation plays an important role in the recrystallization kinetics and final grain size. Therefore, to understand this behavior, the roll cast aluminum alloy was cold rolled from two distinct starting conditions: as-cast and heat-treated (homogeneized) conditions. It was shown that recrystallization was delayed in the sheet rolled from the as-cast condition. Precipitation has occurred simultaneously with recrystallization, in such a manner that dispersoids did precipitate in the deformed microstructure, preferentially, at subgrain boundaries or at free dislocations. As a result, the rearrangement of the dislocations and further recrystallization nucleation has been significantly retarded.
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Dubosq, Renelle. "Assessing the Structural and Alteration Controls on Gold Mineralization at Detour Lake Mine, Ontario, Canada." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36755.
Full textAbstract:
The giant Detour Lake deposit is a Neoarchean orogenic Au ore body located in the
northwestern Abitibi district within the Superior Province. The deposit is situated along the high strain Sunday Lake Deformation Zone (SLDZ) parallel to the broadly E-W trending Abitibi greenstone belt. The lower amphibolite facies assemblage (Act-Bt-Pl-Ep-Alm ±Cal ±Qz ±Ilm) suggests maximum temperatures reaching 550°C, exceeding conditions for pyrite plasticity, an important and ubiquitous Au-bearing phase that may ultimately represent the source for Au at orogenic style Au deposits. The metamorphic assemblage also obscures the relationship between Au and biotite, a visual indicator mineral within Au-rich ore zones. This work combines microstructural, geochemical and geochronological analyses to assess the influence of regional scale deformation and alteration on Au mineralization. EBSD and LA-ICP-MS analyses on pyrite reveal Au enrichment at microstructures supporting a syn- to post-peak metamorphic and
deformation-assisted Au upgrading model. EMPA and 40Ar/39Ar analyses on biotite reveal one chemically homogeneous population, which yield variably reset ages that post-date regional metamorphism and Au mineralization.
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Fazal, Mohammed. "Understanding the microstructural efects in a large grain cast nickel-based superalloy." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/understanding-the-microstructural-efects-in-a-large-grain-cast-nickelbased-superalloy(a6255d81-ba70-48ed-a5bc-917ae1e95fb4).html.
Full textAbstract:
Scatter observed in the fatigue test results of a cast nickel-based superalloy may arise from its coarse grain microstructure. With only a few grains through the sample cross-section, it has been postulated that the inherent anisotropy of individual grains results in the different surface strain distributions during testing. Crystal plasticity finite element modelling (CPFEM) was used to model the deformation of a fat test piece containing a few grains in the cross-section. The mesh was generated using EBSD maps from the surfaces of samples that were subjected to monotonic and cyclic loading at two different temperatures. Digital image correlation (DIC) was used to study the local strain the same sur- faces. Heterogeneous strain distribution, that could be responsible for scatter in the fatigue test results, was observed both in the model and experimentally. However, they were quantitatively different. These differences are attributed to the simplistic microstructural representation in the model and its inability to accurately represent intergranular deformation. The inherent anisotropy within grains resulted in different surface strain distributions during cyclic loading and it was observed that the fatigue life of the test specimens could be correlated to the maximum plastic strain in the sample at the end of the first cycle. As the CPFE model captured the maximum strain measured experimentally, the maximum strain at the end of the first cycle was determined as a fatigue indicator parameter (FIP) for the number of cycles to failure. Randomly generated synthetic microstructures were then loaded in tension and it was observed that when using local strain as a FIP, the scatter in orientations of individual grains resulted in scatter in the expected fatigue life.
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Juan, Pierre-Alexandr. "Twinning in hexagonal materials: application to zirconium and magnesium." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53945.
Full textAbstract:
The main objective of this thesis is to investigate and quantify the influence of parent-twin and twin-twin interactions on the mechanical response of hexagonal close-packed metals. To study parent-twin interactions, a mean-field continuum mechanics approach has been developed based on a new twinning topology in which twins are embedded in twinned grains. A first model generalizing the Tanaka-Mori scheme to heterogeneous elastic media is applied to first and second generation twinning in magnesium. In the case of first generation twinning, the model is capable of reproducing the trends in the development of backstresses within the twin domain as observed experimentally. Applying the methodology to the case of second-generation twinning allows the identification, in exact agreement with experimental observations, of the most likely second-generation twin variants to grow in a primary twin domain. Because the elastic behavior assumption causes internal stress level magnitudes to be excessively high, the first model is extended to the case of elasto-plasticity. Using a self-consistent approximation, the model, referred to as the double inclusion elasto-plastic self-consistent (DI-EPSC) scheme, is applied to Mg alloy polycrystals. The comparison of results obtained from the DI-EPSC and EPSC schemes reveals that deformation system activities and plastic strain distributions within twins drastically depend on the interaction with parent domains.
The influence of twin-twin interactions on nucleation and growth of twins is being statistically studied from zirconium and magnesium electron back-scattered diffraction scans. A new twin recognition software relying on graph theory analysis has been developed to extract all microstructural and crystallographical data. It is capable of identifying all twinning modes and all twin-twin interaction types occurring in hexagonal close-packed materials. The first results obtained from high purity Zr electron back-scattered diffraction maps reveal that twin-twin interactions hinder subsequent twin nucleation. They also show that mechanisms involved in twin growth may differ significantly for each twinning mode. A second study performed on AZ31 Mg presents statistics about low Schmid factor {10-12} tensile twins and about {10-12}-{10-12} sequential double twins coupled with a simplified version of the Tanaka-Mori scheme generalized to heterogeneous elasticity with plastic incompatibilities.
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Kim-Hak, Olivier. "Étude de la nucléation du SiC cubique sur substrats de SiC hexagonaux à partir d’une phase liquide Si-Ge." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10140.
Full textAbstract:
L'objectif de ce travail était de comprendre les mécanismes menant à la formation de SiC-3C sur substrats de SiC hexagonaux lors de la croissance par mécanisme Vapeur-Liquide-Solide (VLS) à partir d'une phase liquide Si-Ge. Notre étude s'est concentrée sur les premiers instants de l'interaction liquide/SiC, c'est-a-dire sans ajout de phase gazeuse réactive (propane). Nous avons montré qu'il se formait très rapidement des îlots de SiC-3C à la surface des germes. L'étude en fonction de divers paramètres (température et durée de plateau, vitesse de chauffage, nature du germe) a permis de mettre en évidence l'influence prononcée du creuset en graphite dans lequel est confinée la réaction. Les observations expérimentales associées à des calculs thermodynamiques ont permis de montrer que l'étape prépondérante, pour la formation du 3C, est sans doute la réaction transitoire entre un liquide très riche en germanium et le germe de SiC. Des considérations d'ordre cinétiques sont cependant à prendre en compte pour expliquer le caractère hors équilibre de la réactionThe aim of this work was to understand the mechanisms that lead to the 3C-SiC formation on hexagonal SiC substrates during the Vapor-Liquid-Solid (VLS) growth from a Si-Ge liquid phase. Our study focused on the early stages of the liquid/SiC interaction, i.e. without reactive gaseous phase (propane) addition. We have shown that 3C-SiC islands were very rapidly formed upon seeds surface. The study of several parameters (such as temperature and duration of the plateau, heating rate, nature of the seed) evidenced the huge influence of the graphite crucible that contains the reaction. Experimental observations combined with thermodynamic calculations show that the most important step for the 3C formation, is the transient reaction between a germanium very rich liquid and the SiC seed. Kinetic effects have to be taken into account to explain the out-of-equilibrium nature of the reaction
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Cagna, Céline. "Influence des gaz de fission sur l'état mécanique des combustibles oxydes irradiés." Thesis, Paris, ENSAM, 2016. http://www.theses.fr/2016ENAM0033/document.
Full textAbstract:
L'irradiation génère dans le combustible des gaz de fission, principalement xénon et krypton, présents sous forme dissoute et sous forme de bulles. L’objectif de ces travaux de recherche est de contribuer à la méthodologie de caractérisation de ces bulles et d’apporter ainsi des éléments de validation de référence pour la modélisation. Deux approches sont étudiées. Sur la base d’une méthode existante de détermination de la pression moyenne des bulles par le couplage de trois techniques : EPMA, MEB et SIMS, une nouvelle méthode complémentaire a été mise au point sur une bulle isolée sous la surface. La méthodologie consiste à repérer une bulle fermée et remplie en xénon par des cartographies microsonde et images MEB et de mesurer la quantité de gaz présent par SIMS. Une observation 3D, par abrasion FIB, donne une estimation du volume de la bulle et permet ainsi de calculer la pression de gaz. A 300 K, une estimation des niveaux de pression est obtenue, sur des bulles intragranulaires, micrométriques du centre de pastilles de combustibles irradiés. En parallèle, une méthode de mesure du champ de déformation élastique engendré par la présence de bulles pressurisées, est développée par HR-EBSD. Un modèle par éléments finis permet d’évaluer les niveaux de déformation autour des bulles de gaz de fission et met en évidence que seules les bulles nanométriques engendrent des déformations élastiques mesurables par cette technique. Au préalable, la méthode a été calibrée à partir d’essais de flexion quatre points sur du silicium monocristallin et sur des céramiques implantées en xénon, permettant une exploitation étendue de la méthode par la prise en compte de déformations libres. Cette étape définit les paramètres d’acquisition et de traitement optimum pour son application sur combustible irradié. La mesure de déformation élastique par HR-EBSD sur combustible irradié reste une mesure relative qui demandera davantage de réflexion quant au choix de la référenceThe irradiation generates in the fuel, fission gases, mainly xenon and krypton, present in dissolved form and in the form of bubbles. This research objective is to contribute to the fission gas bubbles methodology of characterization and thus to bring elements of reference for the models validation. Two approaches are studied. Based on an existing method of bubbles average pressure evaluation by the coupling of three techniques: EPMA, SEM and SIMS, a new complementary method has been developed on an isolated bubble under the surface. The methodology consists in identifying a closed and filled bubble with xenon by microprobe mapping and SEM images and to measure the amount of present gas by SIMS. 3D observation by FIB abrasion provides an estimation of the bubble volume and thus allows to calculate the bubble pressure. At 300 K, an estimation of the pressure levels is obtained on intragranular micrometric bubbles from the fuel pellets center area. Meanwhile, a method of elastic field strain measurement, produced by the presence of pressurized bubbles, is developed by HR-EBSD. A finite element model evaluates the levels of strain around the fission gas bubbles and shows that only nanometric bubbles generate measurable elastic strain by this technique. First, the method was calibrated from four points bending tests on monocrystalline silicon and ceramics implanted with xenon, allowing to take into account free strains. This step defines the parameters of acquisition and optimum treatment for its application on irradiated fuels. Measurement of elastic strain with HR-EBSD on irradiated fuel is a relative measure that will require further consideration in the choice of the reference
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Mineur, Marie. "Conditions locales d'amorçage des fissures de fatigue dans un acier inoxydable de type 316L : aspects cristallographiques (EBSD)." Poitiers, 2000. http://www.theses.fr/2000POIT2266.
Full textAbstract:
Les caracteristiques microstructurales des metaux et alliages metalliques conditionnent fortement les processus de deformation et d'endommagement qui gouvernent leur durabilite en fatigue. Dans ce contexte, nous avons etudie l'influence de la texture cristallographique sur les conditions d'amorcage et de croissance de fissures dans le cas d'un acier inoxydable austenitique 316l teste a 20\c. Pour cela, les caracteristiques cristallographiques locales au niveau d'une population representative de fissures formees en surface ont ete etablies par diffraction des electrons retrodiffuses (ebsd). L'analyse des resultats montre qu'a la fois l'activite des systemes de glissement et les conditions locales d'emergence en surface des bandes de glissement controlent l'amorcage de fissures transgranulaires. Les fissures intergranulaires ou s'amorcant aux joints de macle dependent des desorientations relatives et de l'activite de glissement de part et d'autre des joints. Les domaines angulaires (inclinaison des plans de glissement, directions de glissement, desorientation,) particulierement favorables a l'amorcage ont ete determines pour chaque type de fissure. De plus, des analyses comparatives conduites sur des echantillons testes sous air et sous vide revelent que le processus d'amorcage depend egalement d'effets d'environnement couples aux conditions locales de deformation en surface. Enfin, on met en evidence que les premiers stades de croissance des microfissures sont egalement gouvernes par les conditions locales de surface qui regissent l'amorcage de fissures.
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French, Marsha. "Quartz growth : understanding porosity-preserving microcrystalline quartz through EBSD, TEM, and NanoSIMS examination of low temperature silica." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/7157/.
Full textAbstract:
Deeply buried sandstones in sedimentary basins typically have low porosity due to cementation and compaction. Formation of microcrystalline quartz has proven to be effective at preserving porosity in deeply buried sandstone petroleum reservoirs, typically cemented by syntaxial quartz cement. There remains much uncertainty about what controls the growth of microcrystalline quartz and how it prevents syntaxial quartz overgrowths. Here, the Cretaceous Heidelberg Formation, Germany, and the Oligocene Fontainebleau Formation, Paris Basin, France, provide a natural laboratory to study silica polymorphs and develop an understanding of their crystallography, paragenetic relationships, and growth mechanisms, leading to a new understanding of the growth mechanisms of porosity-preserving microcrystalline quartz. Data from scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) data illustrate that porosity-preserving microcrystalline quartz cement is misoriented with respect to the host grain upon which it grows. In contrast, ordinary quartz cement grows in the same orientation (epitaxially) as the host quartz sand grain, and typically fills pore spaces. EBSD and TEM observations reveal nanofilms of amorphous silica (~ 50-100 nm in thickness) between the microcrystalline quartz and the host grain. The microcrystalline quartz is interpreted to be misoriented relative to the host grain, because the amorphous silica nanofilm prevents growth of epitaxial quartz cement. Instead, the microcrystalline quartz is similar to chalcedony with [11-20] perpendicular to the growth surface and c axes parallel with, but randomly distributed (rotated) on, the host quartz grain surface. Development of pore-filling quartz growing into the pore (in the fast-growing c-axis direction) is thus inhibited due to the amorphous silica nanofilm initially and, subsequently, the misoriented microcrystalline quartz that grew on the amorphous silica. High precision, in situ oxygen isotope analyses of Cretaceous Heidelberg Formation detrital grains and quartz cements show three varieties of authigenic silica growing on detrital quartz grains. Interpretation of these data show that quartz overgrowths grew from meteoric water at about 80°C followed by concentric bands of silica cements. A thin layer of chalcedony was first deposited on both detrital quartz grains and quartz overgrowth cements followed by microcrystalline quartz; this cycle was then repeated. If it is assumed that the closely-related chalcedony and microcrystalline quartz grew from the same water, then isotope data suggest that chalcedony grew at approximately 34°C while microcrystalline quartz grew at approximately 60°C from meteoric water. To further understand the role of chalcedony in microcrystalline quartz growth, chalcedony in two agates from the Citronelle Formation in Louisiana and Lake Superior in Michigan, were studied This study concludes that the bands formed as a result of discrete influxes of siliceous fluid. Within these individual bands there is a sequence of minerals; chalcedony-A (with amorphous silica and nanocrystalline quartz) à chalcedony-MQ (with microcrystalline quartz) à quartz. This paragenetic sequence suggests a viable model for the growth of chalcedony in agates, which helps explain the growth of chalcedony and microcrystalline growth in sandstones. Now that we know what controls microcrystalline quartz growth and why it preserves porosity, it can be used to help identify, rank and appraise deeply buried petroleum accumulations.
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Rault, Vincent. "Analyse locale de la corrosion des renforts métalliques dans les pneumatiques exposés à des environnements représentatifs : vers un modèle prédictif." Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS022.
Full textAbstract:
Le sujet de thèse concerne l’analyse et la prédiction de la corrosion des renforts métalliques exposés dans des environnements représentatifs. Dans cette étude, le système va se complexifier en commençant à partir du renfort métallique délaitonné (acier perlitique) en passant par le renfort métallique laitonné (couche de laiton) pour finir avec le renfort métallique sulfuré (couche de sulfures). Cette approche permet de comprendre pas à pas les phénomènes de corrosion ainsi que l’interaction entre les différentes couches. Les matériaux de l’étude sont caractérisés au départ par des techniques de microscopies (MEB-EBSD, MET) et d’analyses de surface (XPS, Auger). Ces informations microstructurales et de composition chimique sont essentielles pour l’interprétation des essais de corrosion. Les essais électrochimiques sont ensuite réalisés dans 0,1M NaCl pour observer et quantifier le comportement en corrosion des trois types de renforts de l’étude. La quantification est un élément important pour établir des modèles prédictifs de corrosion. Deux types de techniques électrochimiques sont utilisés, les mesures à l’échelle globale (Voltampérométrie, Impédance électrochimique, couplage galvanique…) et les mesures à l’échelle locale (microcellule). Les essais à l’échelle locale sont directement reliés aux cartographies EBSD grâce à la microcellule. Un lien direct microstructure-corrosion est donc établi. A partir des essais électrochimiques, des analyses de solutions (SAA, ICP…) ainsi que des mesures de pH localisées sont réalisés pour quantifier les espèces passant en solution. Ces résultats sont des données d’entrée pour définir un milieu représentatif. De nouveaux essais électrochimiques sont enfin effectués dans le milieu représentatif pour étudier l’impact de ce nouveau milieu sur la corrosion des renforts métalliquesThis work deals with analysis and corrosion prediction of steel cords exposed in representative environments. In this study, the system will become more and more complex starting from “délaitonné” metal reinforcement (perlitic) via the brass metal reinforcement (brass layer) to finish with the metal reinforcement sulfide (sulfide layer). This approach allows you to understand step by step corrosion phenomena and the interaction between different layers. Materials of the study are first characterized by microscopy techniques (SEM-EBSD, TEM) and surface analysis (XPS, Auger). These microstructural informations and chemical composition are essential for interpretation of corrosion tests. Electrochemical tests are worked out in 0,1M NaCl to observe and quantify corrosion behavior of the three kind of steel cords. Quantification is a significant element to establish predictive corrosion models. Two electrochemical techniques are used, measurements at global scale (voltammetry, electrochemical impedance, galvanic coupling ...) and locally measurements (microcell). Measurements at the local scale are directly linked to EBSD maps thanks to the microcell. A direct link microstructure-corrosion is established. From electrochemical tests, solutions analysis (AAS, ICP ...) and local pH measurements are performed to quantify species passing into solution. These results are input data to define a representative environment.New electrochemical tests are then performed in this representative solution to study the impact of this medium on the steel cords corrosion