Les travaux effectués concernent le développement et la caractérisation de nouveaux alliages de titane à grande déformation, combinant des effets TRIP (« Transformation Induced Plasticity ») et TWIP (Twinning Induced Plasticity »). Ils s’inscrivent dans le cadre de la recherche de technologies plus économiques en termes de coûts énergétiques, nécessitant en particulier le développement de matériaux structuraux légers et performants avec une résistance, une ténacité et une ductilité exceptionnelles. Nous avons d’abord utilisé une approche semi-empirique, combinant calculs théoriques et données expérimentales, comme méthode de conception de ces nouveaux alliages. Basée sur des paramètres électroniques, cette approche permet de contrôler le degré de stabilité de la phase β du titane. Cette métallurgie, appelée métallurgie combinatoire, nous a permis de développer rapidement 3 nouvelles nuances d’alliages, qui sont : le Ti-8.5Cr-1.5Sn, Ti-8.5Cr-1.5Al, et le Ti-10V-4Cr-1Al. Il s’avère que plusieurs mécanismes de déformation sont déclenchés pour accommoder plastiquement le matériau, lors d’une sollicitation mécanique externe. Parmi ces mécanismes, sont présents le maclage {332}⟨113⟩, la martensite sous contrainte, et le glissement des dislocations. Nous avons montré que leur synergie donnée naissance à deux effets, un effet de raffinement microstructural dit « effet Hall & Petch dynamique », et un effet assimilable aux interactions matrice-renforts, appelé « effet Composite ». Nous avons mené ensuite une campagne d’essais balistiques comparative avec d’autres alliages de titane, pour analyser le comportement à l’endommagement, au plus proche d’une potentielle application industrielle. Nous avons montré que les alliages ayant la capacité d’être transformable par déformation sont ceux qui possèdent la ténacité (KIC) et la résilience (KCV) la plus élevée. Enfin, dans une dernière partie, axée sur l’ouverture de cette thématique, nous avons étudié dans un premier temps la transposition de la méthode de conception à un alliage industriel. Puis, dans un deuxième temps, une transposition des effets TRIP/TWIP à des matrices α+β, dont les résultats prometteurs des propriétés mécaniques offrent de nouvelles perspectives. / The work carried out concerns the development and characterization of new high deformation titanium alloys, combining TRIP (Transformation Induced Plasticity) and TWIP (Twinning Induced Plasticity) effects. They are part of the search for more economical technologies in terms of energy costs, requiring in particular the development of lightweight and efficient structural materials with exceptional strength, toughness and ductility. We first used a semi-empirical approach, combining theoretical calculations and experimental data, as a method for designing these new alloys. Based on electronic parameters, this approach makes it possible to control the degree of stability of the β phase of titanium. This metallurgy, called combinatorial metallurgy, allowed us to quickly develop 3 new grades of alloys, which are : Ti-8.5Cr-1.5Sn, Ti-8.5Cr-1.5Al, and Ti-10V-4Cr-1Al. It turns out that several deformation mechanisms are triggered to plastically accommodate the material during an external mechanical stress. Among these mechanisms are the {332}⟨113⟩ twinning, the stress martensite, and the dislocation slip. We have shown that their synergy gives rise to two effects, a microstructural refinement effect called "dynamic Hall & Petch effect", and an effect comparable to the matrix-reinforcement interactions, called the "Composite effect". We then carried out a comparative ballistic test campaign with other titanium alloys, to analyze the behavior to damage, closest to a potential industrial application. We have shown that alloys with the ability to be transformable by deformation are those with the highest toughness (KIC) and resilience (KCV). Finally, in a final part, focusing on the opening of this thematic, we first studied the transposition of the design method to an industrial alloy. Then, a transposition of the TRIP / TWIP effects to α+β matrices, whose promising results of mechanical properties offer new perspectives.Keywords : Titanium alloys, Twinning, Strain-hardening, Deformation microstructure, Martensitic phase transformation.

S960 and S700 are two types of high strength low alloy steels (minimum yield strengths at 960 MPa and 700 MPa, respectively) developed recently by Tata Steel. These steels are typically used in heavy lifting equipment. This research examines the feasibility and characteristics of single pass autogenous laser welding (ALW), multi-pass ultra-narrow gap laser welding (NGLW) of 8 mm thick S960 and 13 mm thick S700 high strength low alloy (HSLA) steels and compared the characteristics of the welds with those of gas metal arc welding (GMAW). The work aims to understand the development of welding induced residual stresses, microstructures, microhardness, tensile properties, bending properties and Charpy impact toughness at different temperatures as produced by different welding techniques (ALW, NGLW and GMAW).Design of experiments and statistical modelling were used to predict and optimise laser welding parameters of S960 and S700 HSLA steels. The contour method was used to measure the 2D distribution of residual stresses of the welded specimens. X-ray diffraction was carried out to measure the surface residual stresses of the welded specimens. The main novel contributions include:(1) Development of welding procedures for ultra-NGLW of HSLA steels. The ultra-NGLW process was successfully applied to the welding of 8 mm thick S960 and 13 mm thick S700 HSLA steels with a very narrow groove (1.2-1.4 mm wide) using a moderate laser power (2-3 kW).(2) Resolving the melt sagging problem for single pass autogenous laser welding of thick section materials. Horizontal (2G) welding position was applied to successfully resolve the melt sagging problem when single pass flat (1G) position ALW was applied to welding a 13 mm thick S700 steel plate. Computational fluid dynamic (CFD) modelling was carried out to understand the dynamic force interactions in the weld pool and the factors affecting the formation of the weld bead profile.(3) Understanding the effects of heat input on the microstructures evolution and mechanical properties of the welded high strength steel joints. The much lower heat input for ALW of 8 mm thick S960 steel and ultra-NGLW of both 8 mm thick S960 and 13 mm thick S700 steels results in the generation of hard martensite in the narrow fusion zone (FZ) and heat affected zone (HAZ), which strengthened the welded joints but deteriorated the toughness of the welded joints. The strengthened narrow FZ and HAZ for both the ALW and ultra-NGLW of 8 mm thick S960 steels demonstrated almost the same tensile strength and elongation as the base material. A relatively high heat input for the ALW of 13 mm thick S700 steel results in the generation of bainite in the FZ, which has almost the same microstructure and hardness as the base material.(4) Understanding the effect of solid-state phase transformation on the residual stresses of the welded specimens. It was demonstrated that the solid-state phase transformation from austenite to ferrite, bainite and martensite changes the magnitude of residual stress in the fusion zone for the welded S700 steel plates. In addition, it also changes the yield strength of the FZ, which also has a significant effect on the welding residual stress. In summary, this work has resulted in a significantly enhanced understanding of the way in which the choice of welding process affects the properties of welded joints in high strength steels. Laser welding was found to offer strengthened welded joints. However, the laser welded joints presented low impact toughness. If the toughness of the laser welded joints can be improved, laser welding will be a promising technique for joining high strength steels.

Orientador: Annete Gorenstein / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T01:04:35Z (GMT). No. of bitstreams: 1 FigueroaCadillo_Robinson_D.pdf: 6828830 bytes, checksum: 25774e9d4bb796e5048a90db527b894e (MD5) Previous issue date: 2007 / Resumo: Em dispositivos eletroquímicos como microbaterias ou dispositivos eletrocrômicos o catodo está presente na forma de filme fino. Com o objetivo de otimizar a performance de tais dispositivos, a pesquisa cientifica e tecnológica tem sido orientada na busca de novos materiais para o catodo. Este trabalho, contudo, propõe-se estudar a influencia da morfologia e da microestrutura do catodo no comportamento eletroquímico das microbaterias. O material escolhido foi o WO3. As amostras foram depositadas por sputtering reativo, e diversos parâmetros de deposição foram variados. Explorou-se a variação da potência durante a deposição e, trabalhou-se com o substrato inclinado, em modo estacionário ou rodante. Utilizaram-se diversas técnicas de caracterização. A técnica de Microscopia de Força Atômica (AFM) foi utilizada para analise de área da superfície, rugosidade, e tamanho de grão. A técnica de microscopia eletrônica MEV-FEG foi utilizada na analise da seção transversal dos filmes. O estudo eletroquímico por cronopotenciometria cíclica com limite de potencial permitiu a obtenção da capacidade de carga/descarga durante diversos ciclos. Foram obtidas amostras com e sem estrutura colunar; além disto, morfologias tipo hélice ou pilares foram conseguidas com rotação do substrato. A capacidade de carga depende fortemente do tipo de morfologia. Os melhores resultados foram obtidos com alta potência, para todas as estruturas / Abstract: In electrochemical devices like microbatteries or electrochromic devices, the cathode is present in thin film form. In order to optimize the performance of these devices, the scientific and technological research has been oriented in the search of new cathode materials. The aim of this work, however, is to study the influence of the cathode morphology and microstructure on the electrochemical behavior of microbatteries. WO3 was chosen as the thin film compound. The samples were deposited by reactive sputtering, and several deposition parameters were varied. The power during deposition was fixed in different values, and the samples were deposited with inclined substrates either stationary or rotating. Atomic Force Microscopy was used in order to obtain the surface area, roughness and grain size. Scanning electron microscopy was used in the analysis of the cross sections. The electrochemical study using chronopotentiometry with potential limits allowed the obtention of the charge/discharge capacity during several cycles. Depending on the deposition conditions, samples with or without columnar structures were obtained; also, helicoidal or pillar morphologies were attained with the rotation of the substrate. The charge capacity is strongly dependent on the morphology. The best results were obtained with high power, for all structures / Doutorado / Física / Doutor em Ciências

O objetivo deste trabalho foi estudar as propriedades mecânicas do metal como soldado usando fluxo ativado na condição como recebido. Foram utilizadas cinco chapas base, sendo quatro delas de aço do tipo alta resistência e baixa liga (ABRL) e uma de aço carbono comum SAE 1020, que foram soldadas usando um único passe. O eletrodo utilizado foi o arame EM 12K , diâmetro de 4 mm e pó de ferro 400. As condições de soldagem utilizada foram: tensão de 34V, corrente de 660A, velocidade de soldagem de 30 cm/mim por minuto e uma adição de pó metálico de 373 g/m. Estas condições produzem um aporte de calor de 4,5 kJ/mm e uma diluição da chapa base em torno de 43%. Os ensaios mecânicos realizados forma de dureza, de tração e de impacto. A natureza das inclusões não metálicas foi investigada por microscopia eletrônica de varredura e análise por Energy Dispersive X RAY (EDS). Os resultados mostraram que as condições do fluxo e a diluição da chapa base alteraram a química nos metais como soldados, principalmente o oxigênio, isto permitiu mudanças significativas na temperabilidade. Como resultado as percentagens das microestruturas foram bastante alteradas principalmente na ferrita acicular, ocasionando mudanças nas propriedades mecânicas de dureza, tração e impacto. / The objective of this work was to study the properties of the metal as welded using activated flux in the condition as received. Five base plates, four of which were HSLA steel and one SAE 1020, that were welded using a single pass. EM 12K electrode and 400 metallic powder were used. The conditions for welding were: voltage 34V, current 660A, welding speed 30 cm/min and addition of metallic powder 373 Kg/M. These conditions produced a heat input of 4,5 kJ/mm and dilution in the base plate around 43%. Mechanical tests of hardness, impact resistance and tensile strength were carried out. The nature of non-metallic inclusions was investigated by scanning electron microscopy and analysis by Energy Dispersive X-Ray (EDS). The results showed that the conditions of the flux and the dilution of the base plate changed the chemical compositions in the metal as welded, mainly oxygen, which altered significantly the hardenability. As a result, the percentage of the microstructures changed, specially for acicular ferrite, allowing for changes in mechanical properties of hardness, impact resistance and tensile strength.

No description available.

The goal of this study was to identify and describe different microstructures observed in samples from two major shear zones in the Gällivare area, namely the Nautanen Deformation Zone (NDZ), and the Fjällåsen deformation zone (FDZ). Thirteen samples were examined during this study. The samples represent metavolcanic sedimentary rocks with felsic composition containing mostly quartz, K-feldspars and plagioclase with some accessory minerals such as allanite, monazite, biotite, muscovite, calcite, chlorite etc. and these rocks preserve in some cases mylonitic textures. Two metamorphic events (M1 and M2) and four deformation phases (D1, D2, D3 and D4) were identified. Beginning with the regional metamorphic event M1, which also is peak metamorphism (greenschist to amphibolite facies), resulting in D1, a compressional deformation creating the penetrative foliation S1 from a N-S to NNW-SSE shortening direction. A tectonic pause is followed by M2 synchronous with intrusions of Lina granites resulting in widespread contact metamorphism and reactivation of the shear zones. This new compression has tilted the foliations with a dip of ~60°W of FDZ and ~60°E of NDZ. This also created a SC-fabric, a related S2 foliation which shows a slight WSW tilting, and records reverse dip-slip, ENE dextral movement. A last compressional deformation, D3, generated brittle-plastic deformations observed W of FDZ as a reverse thrust of the Gällivare block upon the W block. The last deformation described, D4, has resulted in a set of fractures, some of which have been quartz filled. These are only observed E of NDZ and were interpreted as post metamorphic brittle deformation in a normal fault motion.

Les microcavités à semiconducteurs apparaissent aujourd’hui comme une plateforme particulièrement propice à l’étude des fluides quantiques en interactions. Dans ces cavités, la lumière et les excitations électroniques sont confinées dans de petits volumes et leur couplage est rendu si fort que les propriétés optiques sont gouvernées par des quasi-particules hybrides lumière-matière appelées polaritons de cavité. Ces quasi-particules se propagent comme des photons, mais interagissent avec leur environnement via leur partie matière. Elles peuvent occuper massivement un même état quantique et se comporter comme une onde macroscopique cohérente et non-linéaire. On parle alors de fluide quantique de lumière. Dans cette thèse, nous étudions la dynamique de fluides quantiques de polaritons dans différentes microstructures unidimensionnelles. La technologie de gravure de microcavités planaires, développée au C2N, permet de réaliser une ingénierie complète du potentiel dans lequel nous générons ces fluides de polaritons et d’implémenter des géométries complexes. Dans une première partie, nous avons étudié les propriétés de localisation des états propres de réseaux synthétiques quasi-périodes. L’exploration théorique du diagramme de phase de localisation des modes propres a dévoilé une nouvelle transition de type délocalisation-localisation lors d’une déformation originale d’un quasi-cristal, transition que nous avons pu observer expérimentalement. Une deuxième partie de la thèse est consacrée à l’étude de la dynamique non-linéaire de deux fluides contra-propageant dans un canal unidimensionnel. La compétition entre énergie cinétique et énergie d’interactions conduit alors à l’apparition de solitons sombres, dont le nombre discret et la position peuvent être contrôlés optiquement. Nous avons mis en évidence une bistabilité contrôlée par la différence de phase imprimée sur les deux fluides. La dernière partie du travail concerne l’étude des non-linéarités pour un fluide de polaritons occupant une bande plate. L’énergie cinétique du fluide y est nulle, si bien que sa propagation est gelée. Nous observons alors la formation de domaines non-linéaires de taille quantifiée. Ce travail ouvre des perspectives prometteuses, tout particulièrement pour l’exploration de phases topologiques de bosons en interactions. De plus, augmenter les interactions permettrait d’utiliser notre plate-forme comme un simulateur quantique. / Semiconductor microcavities have emerged as a powerful platform for the study of interacting quantum fluids. In these cavities, light and electronic excitations are confined in small volumes, and their coupling is so strongly enhanced that optical properties are governed by hybrid light-matter quasiparticles, known as cavity polaritons. These quasiparticles propagate like photons and interact with their environment via their matter part. They can macroscopically occupy a single quantum state and then behave as an extended coherent nonlinear wave, i.e. as a quantum fluid of light. In this thesis, we study the nonlinear dynamics of polariton quantum fluids in various one-dimensional microstructures. The possibility to etch microstructures out of planar cavities, a technology developed at C2N, allows full engineering of the potential landscape for the polariton fluid, and implementing complex geometries. In a first part, we have studied the localization properties of the eigenstates in synthetic quasiperiodic lattices. Theoretical exploration of the localization phase diagram revealed a novel delocalization-localization transition in an original deformation of a quasicrystal and we have experimentally evidenced this transition. A second part of the thesis is dedicated to the study of the nonlinear dynamics of two counterpropagating polariton fluids in a one-dimensional channel. The interplay between kinetic and interaction energy is responsible for the formation of dark solitons, whose number and position can be controlled by optical means. We have evidenced a bistable behaviour controlled by the phase twist imprinted on the two fluids. The last part of this work addresses the study of nonlinearities for a fluid injected in a flat band. Therein, the kinetic energy of the fluid is quenched, so that propagation is frozen. We then observe the formation of nonlinear domains with quantized size. This work opens us exciting perspectives, specifically towards the exploration of topological phases of interacting bosons. Enhancing interactions would also allow using our platform for quantum simulation.

Die Arbeit beschreibt die Entwicklung und Evaluierung einer Technologieplattform für die Herstellung von oberflächennahen Mikrostrukturen mit hohen Aspektverhältnissen. Grundlage dieser Technologieplattform stellt ein neuartiges Konzept zur mechanischen und elektrischen Kontaktierung beweglicher Elemente mittels spezieller Träger dar, deren typische Breite unterhalb eines Mikrometers liegt. Basierend hierauf werden drei unterschiedliche Prozessabläufe zur Herstellung der Mikrostrukturen, auch als Air gap Insulated Microstructures (AIM) bezeichnet, vorgestellt. Der Schwerpunkt dieser Arbeit liegt dabei auf der mehrschichtigen Trägervariante mit Isolationsebene und Leitungsebene. Verschiedene Schichtkombinationen, bestehend aus Siliziumnitrid, Siliziumdioxid und Aluminium, sind in ihrem mechanischen, thermischen und Langzeitverhalten charakterisiert und im Hinblick auf ihre Anwendbarkeit für die Träger bewertet. Für die Strukturierung der Siliziumelemente wird ein Verfahren basierend auf einem CF-Polymer als Passivierungsschicht beschrieben. Neben verschiedenen Ausfallmechanismen für die Passivierung werden gezielte Optimierungen der Abscheide- und Ätzprozesse erläutert sowie deren Resultate dargestellt. Für die vollständige Trennung von Substrat und seismischer Masse ist eine isotrope, vom Aspektverhältnis nahezu unabhängige Siliziumstrukturierung nötig. Entsprechende Betrachtungen und Untersuchungen hierzu, unter Verwendung der Reaktionsgase SF6 und O2, stellen den Abschluss der Untersuchungen zur Prozessentwicklung dar. Um die Leistungsfähigkeit der Technologieplattform zu demonstrieren, erfolgt die Herstellung verschiedener Sensoren und Aktoren. Die Charakterisierung dieser Elemente in ihrem mechanischen, thermischen und Langzeitverhalten stellt den Abschluss dieser Arbeit dar.

Localization of deformation occurs in Earth's crust as a consequence of applied stress and is widespread phenomenon that can be found in crustal rocks. Such localization of deformation can be mostly seen in a form of shear zones. Small shear zones referred as shear bands or S-C structures are often used as kinematic indicators. However, the evolution and kinematic continuity of such structures is not well identified, which makes it problematic when interpreting regional geodynamic evolution. Two possible cases were distinguished and described in this thesis: a) kinematically discontinuous S-C structures formed during two deformation events and b) kinematically continuous S-C structures formed during single deformation event. Kinematically unrelated S-C structures were studied in westernmost part of Tauern Window in Eastern Alps and in Gemer-Vepor Contact Zone in Central West Carpathians where previous geodynamic interpretations might have misinterpreted localization structures. Kinematically continuous shear bands were studied in South Armorican Shear Zone where the S-C fabrics were originally defined and described (Berthé et al., 1979). Two fabrics that crosscut each other at small angles forming S-C geometries were documented during field work and studied from macroscale down to microscale or...

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Elemental titanium (Ti), niobium (Nb), zirconium (Zr), and iron (Fe) powders were used to fabricate four near-β alloys with non-toxic of composition Ti-34Nb-25Zr, Ti-34Nb-25Zr-0.4Fe, Ti-34Nb-25Zr-1.2Fe, and Ti-34Nb-25Zr-2Fe (wt. %) (TNZ and TNZF) using spark plasma sintering (SPS) of nano-crystalline powders attained by high energy ball milling. The fabricated alloys were compared to Ti-34Nb-25Zr (used as a benchmark alloy in this study) and comparison was made with the commercially used Ti base alloys produced either by conventional methods or powder metallurgy. The powder mixtures were milled for 5 hours using a Simoloyer high energy ball mill with a ball to powder ratio of 10:1 and a rotational speed of 1000 rpm. This was followed by sintering the mechanically alloyed powders at 1100 ºC for 10 minutes with a pressure of 50 MPa and a heating rate of 100 ºC/min using an H-HP D25 spark plasma sintering furnace (FCT System, Germany). The powders were characterised for particle size and crystal structure using SEM and XRD. The consolidated components were characterised with regards to density, microstructure, mechanical properties. The electrochemical behaviour of the alloys was investigated using a Digi Ivy DY2300 series potentiostat. Three corrosion medium, Sodium chloride (NaCl), phosphate buffered saline solution (PBS) and Dulbecco’s modified eagle’s medium that mimic the conditions in the human body were used. Mouse myoblast cell line (C2C12) was used to investigate the biocompatibility of the sintered alloys in 1010x5 mm specimens using standard colorimetric assay MTT. Both electrochemical and biocompatibility test were conducted in triplicates and the results compared with that of the benchmark. Results of mechanical alloying of powder mixtures demonstrated an inhomogeneous structure. Milling for 5 hours resulted in agglomeration of small Fe and Zr particles. Milling for 3 hours resulted in a better distribution of elements compared to longer milling times. Therefore, sintering powders milled for 3 hours would have yielded better results. The densification results were acceptable and ranged between 97-99% of theoretical densities. Although some porosity was observed, especially on the un-etched microstructure. An insignificant decrease in density was observed when 1.2 (wt. %) Fe was added. The sintered samples had microstructures which were not homogenous. However, the addition of Fe yielded a more homogeneous microstructure compared to the one with less Fe. Therefore, TNZF with 2 (wt. %) Fe had a more homogenous microstructure. Sintering at 1100 ºC resulted in undissolved niobium and titanium which were observed in the microstructure as dark and white areas. The hardness of the TNZF alloys were comparable and lied between 373 and 432 Hv. These hardness values are higher than other similar titanium-based alloys fabricated using conventional methods. The addition of Fe to TNZ showed an insignificant decrease in hardness. The addition of Fe was found to decrease the Young’s Modulus of TNZ from 119.1 to 80 GPa with an addition of 2 wt.% Fe. However, an unacceptable reduction (230.91 to 158.2 MPa) in strength was also noticed. Pseudo passivation was observed when the alloys were immersed in 0.9 % Sodium Chloride (NaCl) which could be attributed to the inhomogeneity in the microstructure. The possibility of pitting corrosion was also observed. The alloy containing 2 Fe (wt.%) was found to be more corrosion resistant than the other alloys. The TNZF alloys exhibited better corrosion resistance in 0. 9% NaCl compared to phosphate buffered solution (PBS) and DMEM. The corrosion behaviour in PBS and DMEM cannot clearly be explained from the graphs. The morphology of the corroded samples was almost the same for all the alloys in different corrosion media. The microstructures showed pits which could have been from the pores that acted as initiation sites for pitting. In cell culture for 1 and 7 days, the cell viability for TNZF alloys was greater than that of the control group (TNZ). A significant decrease in cell viability for TNZF was observed in cell culture for 4 days. The addition of Fe on TNZ do not cause toxic effects and show good cell adhesion, indicating in-vitro cytocompatibility. The greatest cell viability of 102±3.0 % for Ti-34Nb-25Zr-2Fe. The analysis of cell morphology indicated good cell-substrate interaction. The TNZF alloys developed in this study can be suitable candidates for orthopaedic implant application due to their low Young’s modulus, corrosion resistance and superior biocompatibility. However, the strength needs significant improvement. The advantage of this biomaterial, when compared to commercial alloys, is the absence of cytotoxicity elements such as Al and V.