Nesta dissertação de mestrado foram utilizadas duas ligas de alumínio (AA1100 e AA5052) para a produção de uma microestrutura final apresentando tamanho médio de grãos menores que um micrometro. Tal fato foi possível através do processo de Accumulated Roll Bonding (ARB). Tais materiais produzidos por ARB, foram caracterizados conforme propriedades mecânicas (microdureza, limite de escoamento e resistência) e microestruturais (tamanho de grão e macrotextura e composição química dos precipitados). O principal resultado para este trabalho foi a produção de tiras de AA 1100 e AA 5052 com tamanho médio de grão de 0,50 ± 0,04 m e 0,42 ± 0,06 m respectivamente. Tal resultado é coerente em comparação à literatura. Com relação aos resultados de textura, tais amostras apresentaram temperatura de recristalização acima de 473K e componente de textura típicas de cisalhamento (tanto para o material oriundo de fábrica como para o material laminado). Tal fato é esperado já que não se utilizou lubrificação durante ensaios de laminação. A propriedade mecânica de microdureza de AA 1100 ficou coerente com a literatura embora as propriedades de limite de escoamento e de resistência possuíram módulos abaixo da literatura. / The present work is related to the production, in a laboratory scale, of a metallic microstructure having a grain size smaller than one micrometer, through the Accumulated Roll Bonding technique(ARB), for two different aluminum alloys, namely AA 1100 and AA 5052. The strips obtained by the ARB technique have been characterized by their mechanical properties (microhardness, yield and tensile strength), and their microstructure (grain size, macrotexture and precipitates chemical composition). The main result of this work has been the rolling of AA1100 and AA5052 strips with an average grain size of 0.5 ± 0.04 m and 0.42 ± 0.06 m respectively. Such results are consistent with the literature. Relative to the texture, the samples presented a recrystallization temperature higher than 473K and typical shear texture components (due to the dry rolling conditions during the ARB). Microhardness of the AA110 was consistent with literature data; however yield and tensile strength presented values that were lower than those observed in the literature.

The bulk metallic glasses (BMGs) are potential metallic materials due to their interesting properties, such as the high strength, high elastic strain limit, and high wear/corrosion resistance. Over the past four decades, a variety of studies have been done on the characteristics of the mechanical, thermodynamic properties of such category of metallic materials, but there still remain many questions about basic deformation mechanisms and their microstructures so far. Molecular dynamics (MD) simulation can provide significant insight into material properties under the atomic level and see a detailed picture of the model under available investigation in explaining the connection of macroscopic properties to atomic scale. MD simulation is applied to study the material properties and the deformation mechanisms in various binary metallic glasses and intended to examine the feasibility of MD simulation to compare the experimental results obtained in our laboratory over the past few years. The gradual vitrification evolution of atom mixing and local atomic pairing structure of the binary Zr-Ni, Zr-Ti alloys and pure Zr element during severe deformation at room temperature is traced numerically by molecular dynamic simulation. It is found that the icosahedra clusters will gradually develop with the increasing of disorder environment of alloys in the Zr-Ni, Zr-Ti systems, forming amorphous atomic packing. Other compound-like transition structures were also observed in transient in the Zr-Ni couple during the solid-state amorphization process under severe plastic deformation. The crystalline pure Zr can be vitrified in the simulation provided that the rolling speed is high enough and the rolling temperature is maintained at around 300 K. On the other hand, the effective medium theory (EMT) inter-atomic potential is employed in the molecular dynamics (MD) simulation to challenge the study of the diffusion properties in the Mg-Cu thin films. The transition of local structures of Mg-Cu thin films is traced at annealing temperatures of 300, 413, and 500 K. Furthermore, the simulation results are compared with the experimental results obtained from the transmission electron microscopy and X-ray diffraction. The gradual evolution of the local atomic pairing and cluster structure is discussed in light of the Mg and Cu atomic characteristics. Lately, the progress of the cyclic-fatigue damage in a binary Zr-Cu metallic glass in small size scale is investigated using classical molecular-dynamics (MD) simulations. The three-dimensional Zr-Cu fully amorphous structure is produced by quenching at a cooling rate 5 K/ps (ps = 10-12 s-1) from a high liquid temperature. The Nose-Hoover chain method is used to control the temperature and pressure to maintain a reasonable thermodynamic state during the MD-simulation process, as well as to bring the imposed cyclic stress on the subsequent simulation process. Both the stress- and strain-control cyclic loadings are applied to investigate the structural response and free-volume evolution. The overall structure would consistently maintain the amorphous state during cyclic loading. The plastic deformation in simulated samples proceeds via the network-like development of individual shear transition zones (STZs) by the reversible and irreversible structure-relaxations during cyclic loading, dislike the contribution of shear band in large-scale specimens. Dynamic recovery and reversible/irreversible structure rearrangements occur in the current model, along with annihilation of excessive free volumes. This behavior might be able to retard the damage growth of metallic glass and enhance their fatigue life.

Ein Verbundwerkstoff aus Titan und Aluminium kann mittels akkumulativem Walzplattieren hergestellt werden. Dabei wird die Dehngrenze angehoben, wenn die Titanlagen nicht abschnüren, sondern laminar bleiben. Die Herstellung eines laminaren Ti/Al-Verbundwerkstoffes ist neu gegenüber den bisherigen Studien. Diese Dissertation beschreibt die Hindernisse und Lösungen, die aus metallphysikalischer Überlegung entstanden und praktisch umgesetzt worden sind. Bei der starken Umformung je ARB-Zyklus neigt das Titan bereits beim zweiten Walzen zur Bildung von Einschnürungen. Das kann durch eine Verringerung der Dickenreduktion je Zyklus sowie durch eine Erhöhung der Verfestigungsrate unterdrückt oder verzögert werden. Walzen mit unterschiedlich großen Ober- und Unterwalzen führt im Vergleich zum symmetrischen Walzen bei gleicher Dickenreduktion zu verstärktem Einschnüren der Titanlagen. Da der Prozess jedoch eine Verringerung der Dickenreduktion erlaubt, ermöglicht er die Zahl der Einschnürungen bei gegenüber dem Quartowalzen gleicher Geschwindigkeit zu verringern. Die spezifische Festigkeit erreicht hierbei einen Wert von auf dem Niveau hochfester Stähle.

O presente trabalho teve como objetivo a caracterização mecânica, microestrutural e inspeção fratográfica do compósito de matriz de alumínio Al-1100 reforçado com partículas de carbeto de silício-SiC (40 μm) fabricados por meio de laminação acumulativa (ARB- do inglês Accumulative Roll Bonding), assim como, para efeito comparativo, foram estudados o Al-1100 processado por ARB sem adição de partículas e Al-1100 como recebido. Ensaio de desgaste microadesivo com esfera fixa e ensaio de tração unidirecional quase estático que foram realizados em amostras sem entalhes e em amostras contendo diferentes geometrias de entalhe. Microscopia óptica, microscopia eletrônica de varredura nos modos: elétrons secundários, elétrons retroespalhados, espectroscopia de energia dispersiva por raios-X e difração de elétrons retroespalhados, difração de raios-X e microtomografia computadorizada foram utilizados para caracterizar as amostras. Os resultados obtidos mostraram êxito da incorporação de partículas de SiC na matriz de Alumínio por meio do processo ARB. Houve ganhos relevantes na resistência máxima à tração, na rigidez e na deformação máxima no momento da ruptura, devido à incorporação de SiCp. Essas propriedades foram bastante influenciadas na presença de concentradores de tensão (entalhes). A resistência ao desgaste do compósito foi excepcionalmente incrementada comparativamente aos demais materiais. Todos os resultados foram corroborados pelas análises microetrutural e fratográficas. / The present study aims to characterize mechanical, microstructural and through fractographic inspection laminates Al-1100 aluminum matrix composite reinforced with silicon carbide particles, SiCp (40 μm), manufactured by accumulative roll bonding (ARB), as well as, for comparative effect, were studied Al-1100 processed by ARB without the addition of particles and Al-1100 received. Micro-adhesive wear test with fixed ball and test almost static unidirectional traction were performed on samples without scoring, and in samples containing different geometries notches. Optical microscopy, scanning electron microscopy modes: secondary electrons, backscattered electrons, energy dispersive X-ray and electron backscatter diffraction, X-ray diffraction and computed microtomography, these were used to characterize the samples. The results indicated successful incorporation of SiC particles in the aluminum matrix by ARB process. There have been significant gains in maximum tensile strength, stiffness and maximum deformation at the time of rupture, due to incorporation of SiCp. These properties were strongly influenced in the presence of stress concentrators (notches). The resistance of the composite wear was exceptionally increased compared to Al-1100 ARB. All results were corroborated by microstructural and fractographics analysis.

Nesta dissertação de mestrado foram utilizadas duas ligas de alumínio (AA1100 e AA5052) para a produção de uma microestrutura final apresentando tamanho médio de grãos menores que um micrometro. Tal fato foi possível através do processo de Accumulated Roll Bonding (ARB). Tais materiais produzidos por ARB, foram caracterizados conforme propriedades mecânicas (microdureza, limite de escoamento e resistência) e microestruturais (tamanho de grão e macrotextura e composição química dos precipitados). O principal resultado para este trabalho foi a produção de tiras de AA 1100 e AA 5052 com tamanho médio de grão de 0,50 ± 0,04 m e 0,42 ± 0,06 m respectivamente. Tal resultado é coerente em comparação à literatura. Com relação aos resultados de textura, tais amostras apresentaram temperatura de recristalização acima de 473K e componente de textura típicas de cisalhamento (tanto para o material oriundo de fábrica como para o material laminado). Tal fato é esperado já que não se utilizou lubrificação durante ensaios de laminação. A propriedade mecânica de microdureza de AA 1100 ficou coerente com a literatura embora as propriedades de limite de escoamento e de resistência possuíram módulos abaixo da literatura. / The present work is related to the production, in a laboratory scale, of a metallic microstructure having a grain size smaller than one micrometer, through the Accumulated Roll Bonding technique(ARB), for two different aluminum alloys, namely AA 1100 and AA 5052. The strips obtained by the ARB technique have been characterized by their mechanical properties (microhardness, yield and tensile strength), and their microstructure (grain size, macrotexture and precipitates chemical composition). The main result of this work has been the rolling of AA1100 and AA5052 strips with an average grain size of 0.5 ± 0.04 m and 0.42 ± 0.06 m respectively. Such results are consistent with the literature. Relative to the texture, the samples presented a recrystallization temperature higher than 473K and typical shear texture components (due to the dry rolling conditions during the ARB). Microhardness of the AA110 was consistent with literature data; however yield and tensile strength presented values that were lower than those observed in the literature.

Ein Verbundwerkstoff aus Titan und Aluminium kann mittels akkumulativem Walzplattieren hergestellt werden. Dabei wird die Dehngrenze angehoben, wenn die Titanlagen nicht abschnüren, sondern laminar bleiben. Die Herstellung eines laminaren Ti/Al-Verbundwerkstoffes ist neu gegenüber den bisherigen Studien. Diese Dissertation beschreibt die Hindernisse und Lösungen, die aus metallphysikalischer Überlegung entstanden und praktisch umgesetzt worden sind. Bei der starken Umformung je ARB-Zyklus neigt das Titan bereits beim zweiten Walzen zur Bildung von Einschnürungen. Das kann durch eine Verringerung der Dickenreduktion je Zyklus sowie durch eine Erhöhung der Verfestigungsrate unterdrückt oder verzögert werden. Walzen mit unterschiedlich großen Ober- und Unterwalzen führt im Vergleich zum symmetrischen Walzen bei gleicher Dickenreduktion zu verstärktem Einschnüren der Titanlagen. Da der Prozess jedoch eine Verringerung der Dickenreduktion erlaubt, ermöglicht er die Zahl der Einschnürungen bei gegenüber dem Quartowalzen gleicher Geschwindigkeit zu verringern. Die spezifische Festigkeit erreicht hierbei einen Wert von auf dem Niveau hochfester Stähle.:1. Einleitung - hochfeste, verformbare und leichte Halbzeuge für ressourcenschonende Mobilität 2 2. Zielstellung - hochfeste Leichtmetall-Verbundbleche mit feinlamellaren Strukturen und geringer Korngröße 4 3. Grundlagen 7 3.1. Härtungsmechanismen 7 3.2. Ultrafeinkörnige Werkstoffe und Werkstoffkonzepte für den Leichtbau 10 3.3. Akkumulatives Walzplattieren 15 3.4. Titan/Aluminium-Verbundmaterialien durch ARB 18 3.5. Prinzip und Anwendung von Differential speed rolling 21 4. Methoden 24 4.1. Walzen und Akkumulatives Walzplattieren 24 4.2. DSR - Scherwalzen 27 4.3. Metallographische Probenpräparation 29 4.4. Elektronenmikroskopie, EBSD und Korngrößenbestimmung 32 4.5. Zugversuche 34 4.6. Härtemessungen 36 5. Akkumulatives Walzplattieren 38 5.1. Einfluss von Walzenparametern 38 5.1.1.Walzgut- und Walzenvorheizung 38 5.1.2. Zwischenglühung 45 5.1.3. Walzgeschwindigkeit 60 5.1.4. Mechanische Spannung durch Haspelzug 64 5.1.5. Vergleich von Triowalzen und Quartowalzen 70 5.2. Parametersatz und Vergleich des Verbundes mit EinzelmaterialBlechen 77 5.3. Nachwalzen 80 6. DSR / Walzen mit verschiedenen Geschwindigkeiten der Arbeitswalzen 84 6.1. Ermittlung der Scherung beim Walzen mit verschiedenen Geschwindigkeiten der Arbeitswalzen in Abhängigkeit der vorherigen ARB-Zyklen 84 6.2. Entwicklung des Gefüges in homogenen Metallen und Verbundmetallen 88 7. Abschließende Diskussion und Ausblick 100 8. Zusammenfassung 106 9. Literatur 108

L’électronisation de l’industrie a mené à l’augmentation de la pollution électromagnétique pouvant être néfaste pour les systèmes électroniques sensibles et les êtres vivants. L’un des moyens pour limiter la propagation des champs électromagnétiques est l’utilisation d’un blindage. L’étude s’est ainsi focalisée sur l’élaboration à froid d’un composite bimétallique pour le blindage magnétique. Le composite étudié allie les propriétés physiques de l’aluminium et de l’acier via le trilame Al8011/AcierDC01/Al8011. Le trilame est élaboré par colaminage à température ambiante. Il s’est avéré que la qualité de l’adhérence des interfaces Al/Acier et l’architecture du trilame dépendent fortement des paramètres du colaminage. Une préparation minutieuse des tôles et de leurs surfaces concomitantes se révèle être tout aussi importante que le colaminage en lui-même. De plus, au cours du colaminage, la tôle d’acier s’est montrée sensible à des instabilités plastiques qui amènent par la suite à sa striction et à sa fragmentation. Ces instabilités plastiques favorisent l’adhérence grâce à des soudages Al/Al mais n’en sont pas un prérequis. Au niveau de l’efficacité de blindage, le trilame s’est révélé être particulièrement intéressant puisque, grâce à sa composition et à sa structuration, il est capable d’atténuer aussi bien les champs magnétiques basses fréquences (< 1 kHz) que les champs magnétiques de plus hautes fréquences (> 1 kHz). Dans une étude à iso-masse, le trilame a présenté une meilleure efficacité de blindage que les tôles d’Al, de Cu et d’acier. Cependant, la fragmentation de l’acier dans le trilame s’est révélée être néfaste pour le blindage magnétique, nécessitant de faire alors un compromis entre tenue mécanique et efficacité de blindage. / The growth of electronic devices has led to an increase in electromagnetic pollution that can be harmful to sensitive electronic systems and living beings. One of the means of limiting the propagation of electromagnetic fields is the use of shielding. Then, the study focused on the elaboration of a bimetallic composite for magnetic shielding. The studied composite combines the physical properties of aluminum and steel via the Al8011/SteelDC01/Al8011 trilayer. The trilayer is produced by cold roll bonding (CRB). It has been found that the adherence quality of the Al/Steel interfaces and the architecture of the composite heavily depend on the CRB parameters. Careful preparation of the sheet and their concomitant surfaces is just as important as CRB itself. Furthermore, during CRB, the steel sheet was sensitive to plastic instabilities which subsequently led to its necking and fragmentation. These plastic instabilities promote adherence through Al/Al welds but are not a prerequisite. In terms of shielding effectiveness, the bimetallic composite has proved to be particularly interesting. Thanks to its composition and its structuring, it can attenuate both low (< 1 kHz) and high frequency (> 1 kHz) magnetic fields. In an iso-mass study, the composite showed a higher shielding effectiveness than Al, Cu and steel sheets. However, the steel fragmentation in the composite proved to be detrimental to magnetic shielding, then requiring a compromise between mechanical strength and shielding effectiveness.

Le multi-colaminage est connu pour pouvoir créer des composites ayant une résistance mécanique améliorée et coupler les bonnes propriétés des deux métaux utilisés. L’étude s’est focalisée sur l’élaboration à froid et à chaud de deux composites fonctionnels à base d’aluminium : Al6061/ Al5754 et Al6061/Acier IF. Sur le premier composite, une comparaison a été faite entre le procédé classique et le multi-colaminage croisé, où la direction de laminage est tournée de 90° entre chaque passe. Ce dernier s’est avéré plus apte à hyperdéformer et donc à améliorer la résistance mécanique à température ambiante alors qu’une élaboration à chaud limite cette augmentation par rapport au procédé classique. Au niveau de l’architecture des composites, une réalisation à l’ambiante strictionne puis fractionne la phase dure occasionnant une chute de la résistance mécanique pour le second composite, tandis qu’une réalisation en température conserve la stratification et permet la disparition des interfaces pour le premier composite et l’apparition d’intermétalliques pour le second. Enfin, le composite Al6061/Al5754 s’est montré apte à résister à la fissuration à chaud tandis que le composite Al6061/Acier IF est capable de blinder magnétiquement. / The Accumulative Roll Bonding (ARB), consisting in a repetition of roll bonding, is known as a suitable process to work out composite with tailored properties and higher mechanical strength. The present study aimed to develop two functional composites at room and hot temperatures: AA6061/AA5754 and AA6061/IF steel. The first one was developed with both ARB and Cross-ARB (CARB). The Cross-ARB changes the rolling direction by 90° between each pass. As a result, the second process showed higher strength at room temperature. A hotter temperature of process prevented a further enhancement of the strength. According to the temperature of the process, different architectures were obtained. Indeed, ARB at room temperature led to the necking then to the fragmentation of the hard phase and, as a consequence to the collapse of the strength of the composite AA6061/IF steel. The temperature preserved the stratification in the AA6061/AA5754 composite but favored the appearance of intermetallic phase in the AA6061/ IF steel composite. Eventually, the first composite was able to resist to the hot cracking while the second showed magnetic shielding effectiveness.