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1
Breban, Philippe. "Composites aluminium fibres de carbone obtenus par filage." Châtenay-Malabry, Ecole centrale de Paris, 1990. http://www.theses.fr/1990ECAP0130.
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La plupart des composites à matrice métalliques étudiés à l'heure actuelle sont élaborés par trois technologies principales, dont le coût relativement élevé limite les domaines d'utilisation. Pour palier cet inconvénient, nous avons travaillé à mettre au point un procédé de cofilage en phase solide. L’évolution du procédé nous a permis de résoudre les problèmes d'imprégnation du renfort par la matrice. Dans le cadre de l'optimisation des étapes de fabrication, nous avons étudié l'influence des paramètres suivants sur le comportement et les mécanismes d'endommagement du matériau: longueur des fibres, orientation du renfort et fraction volumique locale. Pour cela nous avons développé une démarche de type micro-macro fondée sur la théorie d'inclusion équivalente d'Eshelby. Nous modélisons ainsi l'influence de la microstructure sur les caractéristiques élastiques, les coefficients de dilatation et la surface seuil d'écoulement. Des calculs par éléments finis sur cellules de base à trois phases complète cette approche. Nous regardons l'influence de la répartition des fibres sur le développement de la plasticité locale. Une configuration de fibres proches de leurs voisines a un rôle prépondérant sur la propagation de l'endommagement qui se produit en tête de fibre. Nous proposons un critère analytique d'initiation de cet endommagement qui prend en compte la distribution de fraction volumique locale dans le matériau. Les résultats sont comparés à des essais de traction dans l'enceinte du microscope électronique à balayage, ou nous pouvons suivre les différentes étapes du processus de rupture. L’outil analytique développé est intégré dans une démarche originale de détermination d'une statistique d'endommagement pour une structure. Nous pouvons, ainsi, donner localement la probabilité d'endommagement d'un volume de composite en fonction de l'observation de ses distributions de microstructure, et du chargement
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Chamroune, Nabil. "Matériaux composites Aluminium/Carbone : architecture spécifique et propriétés thermiques adaptatives." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0140/document.
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Les matériaux composites à matrice métallique (CMM) sont actuellement étudiés pour être utilisés dans de nombreux domaines d’application. L’une des applications potentielles concerne leur utilisation en tant que drain thermique pour les modules de puissance. Pour cette application, deux conditions sont requises : une conductivité thermique (CT) élevée pour évacuer la chaleur générée par la puce électronique et un coefficient d’expansion thermique (CTE) proche du substrat céramique (2-8×10-6 /K) utilisé dans le module de puissance.Ainsi des matériaux composites à matrice aluminium (Al : CT de 217 W/m.K et CTE de 24×10-6 /K) et à renfort plaquette de graphite (GF : CT de 1000 W/m.K et CTE de -1×10-6 /K dans le plan de la plaquette) ont été élaborés. Ces matériaux composites ont été fabriqués par Métallurgie des Poudres (MP) conventionnelle mais aussi par un procédé original nommé Flake Powder Metallurgy (FPM). Ce procédé, qui consiste à utiliser une poudre métallique à morphologie plaquette, a permis d’optimiser l’orientation des renforts plaquette dans un plan perpendiculaire à la direction de densification sous l’action d’une pression uniaxiale. De plus, ce procédé a permis d’obtenir une meilleure adhésion entre la matrice et le renfort comparé aux matériaux composites élaborés par MP conventionnelle. Cela a abouti à une amélioration de la CT qui est passée de 400 W/m.K à 450 W/m.K pour un taux de renfort de 50%vol. Néanmoins, concernant la dilatation thermique, des CTE de 21,8×10-6 /K et 21,7×10-6 /K ont été obtenus par MP et FPM respectivement, ce qui est incompatible avec l’application visée.Pour surmonter cette problématique, des matériaux composites à renfort multiple ont été élaborés par frittage en phase liquide. Ainsi des fibres de carbone (FC) ont été rajoutées à l’aluminium et aux plaquettes de graphite. L’ajout de ce second renfort au graphite a permis de diminuer de manière importante le CTE des composites Al/(GF+FC) avec une faible proportion en FC tout en maintenant une haute CT. De plus les matériaux composites Al/(GF+FC) présentent des CTE nettement inférieurs aux composites Al/FC avec un %vol. de FC équivalent. Ainsi des matériaux composites Al/(GF+FC) ont été élaborés par frittage en phase liquide permettant d’obtenir une CT de 400 W/m.K (comparable à la CT du cuivre) et un CTE de 8×10-6 /K (comparable au CTE de l’alumine). De plus la légèreté de l’aluminium confère aux matériaux composites Al/C une faible densité (d=2,4). Par conséquent, les matériaux développés dans cette étude sont prometteur en tant que drain thermique léger, notamment dans le domaine de l’électronique embarquéeMany carbon/metal composites are currently used in several applications. One of them concerns their use as heat sinks in microelectronics. Concerning this application, two conditions are required: a high thermal conductivity (TC) in order to evacuate the heat generated by the electronic chip and a coefficient of thermal expansion (CTE) similar to the used material type of the electronic device (2-8×10-6 /K).Therefore, graphite flakes (GF; TC: 1000 W/m.K and CTE: -1×10-6 /K in the graphite plane) reinforced aluminum matrix (Al; TC: 217 W/m.K and CTE: 25×10-6 /K) composites were fabricated. These composite materials were fabricated by Powder Metallurgy (PM) and Flake Powder Metallurgy (FPM). This process, which consist to use a flattened metallic powder, helped to improve the in-plane orientation (perpendicular to the pressure direction) of GF under uniaxial pressure. Moreover, this process provided a better Al-C interface thanks to a planar contact between the matrix and the reinforcements. This resulted in an improvement of the CT from 400 W/m.K to 450 W/m.K for a reinforcement content of 50 vol.%. Nevertheless, regarding thermal dilation, CTEs of 21.8×10-6 /K and 21.7×10-6 /K were obtained by MP and FPM respectively, which is incompatible with the intended application.To overcome this problem, composite materials with multiple reinforcement were developed by solid-liquid phase sintering. Then, carbon fibers (CF) have been added to aluminum and graphite flakes. The addition of CF to GF reinforcement reduced significantly the CTE of the Al/(GF+CF) composites with a small proportion of CF, while preserving a high TC. In addition, the Al/(GF+FC) composite materials have significantly lower CTEs than the Al/CF composites with a equivalent vol.% of CF. Therefore, Al/(GF+CF) composite materials were developed by solid-liquid phase sintering to obtain a TC of 400 W/m.K (comparable to the TC of copper) and a CTE of 8×10-6 /K (comparable to the CTE of alumina). In addition, the lightweight of aluminum gives composite materials Al/C a low density (d = 2.4 g/cm3). Therefore, the composite materials developed in this study are promising as a lightweight heat sink in microelectronic industries
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Abdullah, Abu. "Machining of aluminium based Metal Matrix Composite (MMC)." Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/34661/.
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The machining of aluminium 2618 particulate reinforced Metal Matrix Composite (MMC) with 18 vol. % silicon carbide (SiC) using cemented carbide cutting tools has been undertaken. Two grades of cemented carbide inserts, uncoated K68 grade and coated KC910 grade (coated with TiC and A1203) having negative and positive rake angles (with and without chip breaker) have been used to machine this material in order to understand the machining process, tool failure modes and wear mechanisms. Turning tests in the speed range 15 - 10 m/min have been carried out at 0.2,0.4 and 0.6 mm/rev feed rates and 2 mm and 4 mm depths of cut. Both cemented carbide tools have been shown to be capable of machining the MMC and give reasonable tool lives. Low speed and high feed rate are found to be a good combination in order to machine this material effectively. Coated KC910 grade inserts with negative rake angle gave the best performance. The use of a chip breaker has no significant effect on the machining process of the NMC because the material is one which inherently short chips due to ductility limitations caused by the particles. Tool failure mode studies showed that the tools failed by flank wear. Tool wear mechanism analysis indicated that abrasion wear was the tool life controlling factor under all cutting conditions. The tool wear is related to the direct contact between the abrasive hard SiC particles and the cutting edge and their relative motion to the rake and clearance face. Hence, the hardness of the SiC particles is a dominant factor for the tool wear. Two separatem odels of abrasio. n haye.b een suggested.B uilt-up edge (BUE) which has a distinct shape was more pro i1ounced at lower cutting speeds, high feed rates and greater depth of cut. The presence of BUE has been found to increase tool life and reduce tool wear but at the expense of surface finish. The increase in tool life or reduction in tool wear is likely due to the protective layer that the BUE formed on the tool surface preventing a direct contact between the tool and chip. Linear regression analysis showed that the value of Taylor exponent n is high (0.8-1.0) compared to the values of n (0.2-0.3) obtained when machining steel. This indicates that the tool life is less sensitive to cutting speed for MMC than it is for steel.
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Melotti, Federico. "A novel aluminium nano-composite with enhanced mechanical properties." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7612/.
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The aim of this study was to develop a new castable and heat treatable alloy, based on the A205 alloy composition, with improved thermal stability at 230 °C. Several unique combinations of alloying elements, chosen from groups IIIB, IVB and VB, up to 0.5 wt. %, were added to the A205 alloy. These elements were chosen to nucleate high temperature precipitates, with a cubic L12 structure. The additions were made in group of two, with one elements being always the zirconium. After 1000 hours holding at 230 °C, several of these alloys resulted to have better mechanical properties when compared to the A205 alloy. The IDEAL alloy was chosen and further studies were carried out. This alloy showed the same tensile proprieties of the A205 alloy at peak-aged condition, while at elevated temperature, the IDEAL alloy had 15 % improved UTS and YS. An investigation was carried out to understand the reasons of this improvement. Two strengthening mechanisms were found. Firstly, the microstructure of the alloy showed a reduced size of the Al-Cu precipitates. Secondly, two different high temperature precipitates were nucleated.
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Tyurin, Yu, O. Ivanov, O. Kolisnichenko, M. Kovaleva, I. Duda, O. Maradudina, and Y. Trusova. "Properties of nanostructured composite titanium coating on aluminium surface." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20488.
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Popineau, Sylvain. "Durabilité en milieu humide d'assemblages structuraux collés type aluminium/composite." Phd thesis, École Nationale Supérieure des Mines de Paris, 2005. http://tel.archives-ouvertes.fr/tel-00159392.
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La présente étude traite de la durabilité (vieillissement) en milieu humide d'assemblages structuraux constituants les tuyères de propulseurs à poudre. Les matériaux utilisés sont un alliage d'aluminium et un matériau composite, collés ensemble par un adhésif polymère.L'adhésif se révèle être la partie la plus sensible à un environnement aqueux. La cinétique de diffusion de l'eau dans la colle semble être décrite convenablement par le modèle mathématique de Carter et Kibler.
La diminution des propriétés mécaniques du polymère massique et des assemblages structuraux semble liée à la pénétration de l'eau. Un modèle permettant d'évaluer indirectement l'énergie d'adhésion, et par extrapolation la résistance des assemblages en fonction du temps de vieillissement a été élaboré à partir du faciès de rupture des éprouvettes et de la cinétique de diffusion d'eau. L'influence d'un traitement organosilane de la surface d'aluminium sablée sur la cinétique de dégradation en milieu humide des assemblages a ensuite été étudiée.
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Miao, Tingyi. "Nacre-like Aluminium Alloy Composite Plates for Ballistic Impact Applications." Thesis, The University of Sydney, 2019. https://hdl.handle.net/2123/21231.
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It is a major scientific challenge to develop the light-weight materials with high performance simultaneously in diverse applications ranging from civil engineering to defence. Numerical results for composite plates of 5.4-mm, 7.5-mm and 9.6-mm thick bioinspired composite plates were compared with corresponding bulk plates under the impact of a rigid hemi-spherical projectile at same impact velocities. The most significant improvement was recorded for the 5.4-mm thick nacre-like aluminium alloy composite plate, which was attributed to the larger area of plastic deformation due to the tablet arrangement. Experiments data were collected to validate the numerical simulation. It has been found that the nacre-like composites of different thickness had better ballistic behaviour than the bulk ones. The aim of this thesis is to give general background and research progress about natural nacre and the corresponding nacre-inspired artificial composites, to provide the basis for preparing the detailed experimental and numerical study on the ballistic performance of nacre-like aluminium alloy composites. My following ballistic experiments are to validate the numerical simulation results that the nacre-like composite plate has better ballistic performance at high velocity due to the tablets arrangement and plastic deformation. From previous simulation results, 5.4-mm nacre-like plate has shown a significant performance improvement compared with same thickness bulk plate owing to the hierarchical structure induced high energy absorptions. Hence, plate thickness and projectile velocity play a significant role on the performance improvement of the proposed nacre-like AA7075-T651 composites. Further experimental works are needed to assess other crucial parameters for modifying the mechanical behaviours of such bioinspired materials.
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Polley, Neal John. "Development of Al-Mgâ‚‚Si in situ composites." Thesis, Brunel University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274812.
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Johannesson, Birgir. "Internal stresses and the cyclic deformation of an aluminium matrix composite." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/843903/.
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The development of internal stresses in planar random Saffil fibre reinforced aluminium with a range of fibre volume fractions has been studied theoretically and in monotonic and cyclic deformation (Bauschinger) experiments at room temperature and 77K. The conventional method of analysing Bauschinger experiments is extended to allow for a separation of the mean and thermal stresses. This analysis is applied to experimental results enabling the mean stress hardening rate and the magnitude of the thermal stress to be measured. The experimental results are compared with predictions of the mean field model, which is based on the Eshelby method of determining internal stresses. For that purpose the Eshelby S tensor for a planar random array of fibres is calculated. Because the aluminium/Saffil composites are not isotropic in the transverse directions, the plastic strain used in the calculations has to be determined experimentally. A method for quantifying the anisotropic plastic flow of the aluminium/Saffil composites is proposed and the results are used in calculations of the mean stress hardening rate. A comparison of predictions for the mean stress hardening rate with results of the experimental analysis proposed here shows that good agreement is obtained for low fibre volume fractions at 77 K. The results also show that relaxation of the mean stress increases with fibre volume fraction and that at 77 K the mean stress hardening rate is about a factor of two larger than at room temperature. The measurements of the thermal stresses obtained in the Bauschinger experiments are in quantitative agreement with results obtained in monotonic tests. The magnitude of the thermal stress at room temperature or 77 K is independent of fibre volume fraction and a comparison with predictions shows that relaxation of the thermal stress increases with fibre volume fraction. Cycling in the Bauschinger experiments reduces the thermal stress and hence the separation of the mean and thermal stresses is essential for a reliable measurement of the mean stress hardening rate. Matrix hardening contributes considerably to the overall hardening of the composite, both at room temperature and 77 K. The modified Orowan-Wilson model, which enables the plastic friction coefficient to be measured in copper-tungsten composites, has been applied to the aluminium\Saffil composites. The model requires both the mean stress and the peak stress curves obtained in Bauschinger experiments to be linear in plastic strain. Most of the peak stress curves for the aluminium/Saffil composites are non-linear but for the curves which are linear the predictions of the model are not in quantitative accord with experimental results. This may be because relaxation reduces the mean stress and the source shortening stress in different proportions. The diameter of the Saffil fibres is also close to the lower end of applicability of the model. The temperature dependence of the mean stress hardening rate suggests that relaxation is thermally activated. A model for relaxation of the mean stress is proposed. An equation is derived for the number of Orowan loops per fibre and it is assumed that the rate controlling mechanism of relaxation is cross slip of screw dislocations. The estimated activation energy is independent of fibre volume fraction but the activation volume decreases with increasing fibre volume fraction. The magnitudes of activation energy and activation volume support the assumptions of the model. A preliminary study on the early stages of fatigue shows that persistent slip bands form in the matrix of the aluminium/Saffil composites.
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Styles, Millicent. "Characterisation of the flexural behaviour of aluminium foam composite sandwich structures /." View thesis entry in Australian Digital Theses Program, 2008. http://thesis.anu.edu.au/public/adt-ANU20080813.170807/index.html.
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Styles, Clinton Mark. "Fracture and fatigue behaviour of a particulate reinforced aluminium based composite." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239454.
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Famodimu, Omotoyosi Helen. "Additive manufacturing of aluminium-metal matrix composite developed through mechanical alloying." Thesis, University of Wolverhampton, 2016. http://hdl.handle.net/2436/620337.
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Laser melting of aluminium alloy - AlSi10Mg has increasingly been used to create specialised products in aerospace and automotive applications. However, research on utilising laser melting of Aluminium matrix composites in replacing specialised parts have been slow on the uptake. This has been attributed to the complexity of the laser melting process, metal/ceramic feedstock for the process and the reaction of the feedstock material to the laser. Thus an understanding of the process, material microstructure and mechanical properties is important for its adoption as a manufacturing route of Aluminium Metal Matrix Composites. The effect of the processing parameters (time and speed) on embedding the Silicon Carbide onto the surface of the AlSi10Mg alloy was initially investigated in Phase 1 and 2 of the research. The particle shape and maximum particle size for each milling time and speed was analysed in determining a suitable starting powder for the Laser Melting phase. An ideal shape and size for the composite powder was obtained at 500 rev/min when milled for 20 mins. The effects of several parameters of the Laser Melting process on the mechanical blended composite were investigated. Single track formations of the matrix alloy, 5% Aluminium Metal Matrix Composites and 10% Aluminium Metal Matrix Composites were studied for their reaction to the laser melting in Phase 3. Subsequently in Phase 4, density blocks were studied at different scan speeds and step-over for surface roughness, relative density and porosity. These were utilised in determining a process window to fabricate near fully dense components. Phase 5 of the research focused on microstructural and mechanical properties of the laser melted matrix alloy using the normal parameters for the matrix alloy and the modified LM parameters for the composite powders. Test coupons were built in one orientation and some coupons were heat-treated to initiate precipitation-hardening intermetallics in the matrix and composite. This study investigates the suitability of the mechanical alloying as a novel method of producing feedstock material for the LM process. This research further explores the interaction of the composite powders with the laser until suitable process parameters were obtained. Furthermore, the fractography, mechanical and microstructural evolution of the Al/SiC composite, with different percentage volume reinforcement manufactured by the LM and subsequently heat treated, was explored for the first time.
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Jiao, Shuai. "Development of an Innovative Composite Mullion Made of Aluminium and Timber." Thesis, Griffith University, 2021. http://hdl.handle.net/10072/401641.
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The façade, as the envelope of a building, provides essential functions such as structural resistance against wind loading, thermal insulation and weather independence. The aluminium-glass curtain wall façade system has become a popular alternative for high-rise buildings due to its aesthetic appeal and efficient unitised installation. In a unitised glass curtain wall façade system, the vertical structural frame, named mullion, is the dominate wind load-bearing element but the critical thermal bridging element. Extruded aluminium mullions have been popularly used due to their high strength to weight ratios, high corrosion resistance and extrudability to allow the façade frames light, durable and flexibly unitised. However, the aluminium mullions might not be so good as some mullions in other aspects, e.g., in thermal performance, aesthetics and sustainability. To address these issues, several attempts to improve their performance, including introducing thermal breaks or structural timber, and hiding the exposed aluminium extrusions, were proposed and evaluated in recent decades. However, none of them could solve all the drawbacks of aluminium mullions. This thesis proposes an innovative aluminium-timber composite mullion, which is durable, unitised, structurally sound, energy-efficient, aesthetically pleasing and sustainable, and aims at its structural and thermal behaviours.
In the structural investigation, three series of experimental tests were firstly conducted to investigate and evaluate the structural behaviour of the novel composite mullions: material property tests, connection tests, and four-point bending tests. Material property tests were done to obtain the mechanical properties of aluminium and timber used in the novel composite mullions. Four types of aluminium-timber connections were subjected to shear loading in the connection tests. The results showed that the proposed adhesive bond formed the optimum connection between aluminium and timber. After determining the connection type, a series of four-point bending tests were conducted using a back-to-back restrained test set-up under both positive and negative loading cases. Furthermore, the traditional aluminium mullions were also tested for comparison. The aluminium mullions failed in local buckling under negative loading, while the composite mullions failed due to plywood compressive yielding and aluminium flange local buckling. Moreover, distortional buckling was observed during aluminium mullion tests subjected to positive loading, while the composite mullions failed due to parallel to the grain tensile failure in the plywood flanges. It was found that the composite mullion had greater structural performance subjected to bending.
Then, a numerical study using finite element models was conducted to further investigate the bending behaviour of the composite mullion based on the experimental results. Two types of finite element models, experimental models and ideal models, were used and validated with the experimental tests. Parametric studies were also performed using validated ideal models to develop the design rules of the composite mullions. The finite element analysis results were then compared with two current design methods: limiting stress method (LSM) and total moment capacity approach (TMCA). It was found that the LSM was too conservative and that the TMCA was only accurate under positive loading with a mean ratio of 1.07 and a COV of 3% for male mullions, 1.09 and 3% for female mullions. Hence, this thesis proposes a modified TMCA using an elastic-plastic approach under negative loading to improve its accuracy. The modified TMCA to predict the negative loading case reached an adequate accuracy with a mean ratio of 0.99 and a COV of 3% for male mullions, and a mean ratio of 1.00 and a COV of 3% for female mullions.
This thesis also evaluates and compares the thermal performance of this novel composite mullion with several current aluminium mullions. It showed that the composite mullion had a much greater thermal performance than the traditional mullion with an improvement of 52%, though it was less energy-efficient than thermally broken aluminium mullion. Furthermore, it was found that the thermal conductance of the composite mullion could be further reduced by four proposed energy-efficient strategies. The optimal combination could reach a reduction of 69% compared with the initial design of the innovative composite mullion. Moreover, a generic study was also performed to investigate the influence of various parameters on the thermal conductance of the composite mullions. The results and evaluation are detailed in this thesis.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Asselin, Daniel. "Influence des defauts sur les propriétés mécaniques du composite Duralcan F3S.20S /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1993. http://theses.uqac.ca.
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Pratapa, Suminar. "Synthesis and character of a functionally-graded aluminium titanate/zirconia-alumina composite." Thesis, Curtin University, 1997. http://hdl.handle.net/20.500.11937/988.
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A functionally-graded Al(subscript)2TiO(subscript)5/ZrO(subscript)2-Al(subscript)2O(subscript)3 (AT/zirconia-alumina) composite has been successfully synthesized by an infiltration process involving an alpha-Al(subscript)2O(subscript)3-ZrO(subscript)2 (90:10 by weight) green body and a solution containing titanium chloride. The mass gain after infiltration has been used to estimate the amount of new phase introduced into the system. The phase composition character of the functionally-graded material (FGM) has been determined by x-ray diffraction. The Rietveld "whole pattern" refinement method was applied to diffraction patterns of the sample which were collected from the surface and at several depths which were made by polishing away the material. Absolute weight fraction determination using the Rietveld external standard method showed that the concentration of AT reduces linearly from the surface to the core. In contrast, the alpha-alumina content increases with depth in a complementary manner. Low level amorphous phase was also observed. Other functionally-graded microstructural profiles examined were x-ray characteristic line intensity of Ti, Ti dot-mapping, and alpha-alumina grain size. The FGM also exhibits graded character in both thermal and mechanical properties, i.e. thermal expansion, microhardness, and Young's modulus. The thermal expansion coefficient (TEC) of the FGM increased with polishing-depth and approached that of the zirconia-alumina reference sample at a depth of 0.5 mm.Relatively lower thermal expansion and softer surface layer in comparison to those of the core (TEC value of 5.9 x 10(subscript)-6 degrees celsius(subscript)-1 and microhardness of 6 GPa compared to 7.4 x 10(subscript)-6 degrees celsius(subscript)-1 and 12 GPa, respectively) render possibilities to implement the material to which thermal shock resistance surface but hard core, such as a metal melting crucible, are required. Load-dependent microhardness was obviously observed on the surface of the material but only slight dependence was observed in the core. This observation indicated that the material exhibit "quasi-ductile" surface but brittle core. In comparison to the reference specimen, the FGM displayed damage-tolerance and remarkable machinability.
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Forde, John. "The elevated temperature performance of cast aluminium alloys and the development of a cast aluminium-copper metal matrix composite." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6419/.
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The first phase of this thesis characterised the currently commercially available L169 and A201 aluminium alloys in terms of their response to testing at the operating parameters predicted for next generation aero-engine components. The L169 and A201 alloys were initially subjected to ageing trials at 205°C, specimens of both alloys were then fatigue tested at ambient temperature and at 205°C following 1000 hours exposure at 205°C. Detailed micrographic characterisation was undertaken to assess the impact of prolonged elevated temperature exposure on the alloy microstructure. Fractography was undertaken on the failed fatigue specimens to assess the impact of ageing temperature and temperature exposure on fatigue behaviour. The L169 alloy exhibited a significant reduction in properties following 1000 hours exposure at 205°C due to extensive precipitate coarsening. The A201 exhibited comparably better elevated temperature performance due to the increased stability of the Ω- phase precipitate however the extensive shrinkage porosity observed in the alloy had a negative impact on fatigue performance and will limit its use in a pressure tight environment. In addition to the investigation into currently commercially available alloys a detailed investigation was taken into a novel dilute aluminium-copper based castable metal matrix composite with the potential for use at elevated temperatures. This alloy exhibits unique solidification mechanisms which result in an increased resistance to conventional aluminium copper alloy casting defects such as shrinkage porosity, segregation and hot tearing. A detailed investigation was undertaken to assess the impact of chemical composition on the alloys unique solidification behaviour and to assess whether there was any possibility for further optimisation. Following on from this investigation the alloy was characterised in similar terms to the L169 and A201 alloys in terms of its fatigue behaviour at both ambient and elevated temperatures to provide an assessment of the alloys potential to meet the predicted next generation aero-engine component operating conditions.
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Subbarayan, Sapthagireesh. "Fabrication of a Novel Al/Mg Composite: : Processing and Characterization of Pure Aluminium, Al/AZ31 Alloy Bi-Metal and Aluminium based Sheet Composites by Severe Plastic Deformation." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23778.
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Madgwick, Alexander. "Creep and damage in an A359 aluminium alloy/SiC metal matrix composite." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620311.
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Mustaffar, Ahmad Fadhlan Bin. "Irregular aluminium foam and phase change material composite in transient thermal management." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3338.
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Traction systems generate high loads of waste heat, which need to be removed for efficient operations. A new transient heat sink is proposed, which is based on salt hydrate phase change material (PCM). The heat sink would absorb heat during the short stationary phase i.e. at stations in which the PCM melts, a process accelerated by aluminium foam as it increases the rate of heat transfer within the PCM. When the train moves, the PCM is solidified via a forced convection stack. This creates a passive and efficient thermal solution, especially once heat pipe is employed as heat conduit. At the outset, the characteristics of the foam needed to be accurately determined. The foam was uncommon as its pore morphology was irregular, therefore it was scanned in a medical computed tomography (CT) scanner, which allowed for the construction of a three dimensional (3D) model. The model accuracy was enhanced by software, resulting in an extremely useful analytical tool. The model enabled important structural parameters to be measured e.g. porosity and specific surface area, which were crucial for the subsequent thermal and fluid flow analyses. A defect dense region was also detected, the effect of which was further investigated. Interestingly in the volume devoid of this defect, the porosity and specific surface area were uniform. A test rig was constructed that mimicked liquid cooling (or in the planned application, heat pipe cooling) in power electronics. At the core was a heat sink of salt hydrate PCM, impregnated within the foam. The sink with its current specifications (with liquid cooling) was able to absorb a thermal load consistent from a group of 4-5 IGBTs, which dissipated a low power of 20W per module during stops. The heating period of 1600-3500s per cycle meant the sink could be fitted to intercity locomotives. The foam increased the effective thermal conductivity by a factor of 24, from 0.45 to 10.83 W/m.K. 3D volume averaged numerical simulation was validated by experiment, which could be used to facilitate scale up or redesign for further optimization. As well as a support structure for the storage component of the system, the foam could replace conventional fins in forced convection, adding value to the potential manufacturer of the system. Heat transfer coefficient calculation incorporated the actual surface area that was derived from the 3D model, a first for metal foam studies. Results have shown a good Nu/Re correlation, comparable with other metal foam works.
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Desjardins, Victor. "Connecteurs en cisaillement pour développer l'action composite dans les ponts aluminium/acier." Master's thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27926.
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Les alliages d'aluminium ont plusieurs propriétés qui rendent intéressantes son utilisation dans les ouvrages d’art, en particulier dans un contexte de climat nordique. En effet, ce matériau a un faible ratio poids/résistance, une très bonne résistance à la corrosion, une résilience élevée à basse température, ainsi qu’une bonne formabilité. Pour ces raisons, l’aluminium est envisagé pour la production de platelages de ponts constitués d’extrusions multicellulaires soudées entre elles. Ces platelages doivent être connectés sur des poutres en acier au moyen d’un assemblage boulonné antiglissement, afin de développer l’action mixte entre le platelage et les poutres. La difficulté de ce projet réside dans la difficulté d’accès à l’intérieur des cellules extrudées. Cela empêche la bonne mise en place des connexions boulonnées antiglissement respectant les exigences de la norme canadienne sur les ponts routiers. Deux solutions sont étudiées : l’utilisation de boulons aveugles et la conception d’une extrusion d’attache entre le platelage et les poutres. Pour chacune de ces solutions, une étude de faisabilité est faite. Dans le cas des boulons aveugles, deux modèles ont été identifiés, puis modélisés par éléments finis afin de déterminer s’ils se conforment aux exigences de la norme CAN/CSA-S6-2014. Dans le cas des extrusions d’attache, deux modèles seront conçus et testés par éléments finis, au regard de la norme. Les solutions explorées dans ce travail sont ensuite comparées par le moyen d’analyses SWOT, afin de mettre en évidences leurs forces, faiblesses, opportunités et menaces. Cela permettra d’aboutir à des recommandations. Mots-clefs 6063-T6, aluminium, assemblage antiglissement, boulons aveugles, CAN/CSAS6-2014, éléments finis, extrusions, platelage, pont.Aluminium alloys have many properties that make this material fit for structural uses, in particular in a nordic climate. This metal has indeed a good weight/resistance ratio, an excellent corrosion resistance, a high resilience at low temperatures, and a good formability. For these reasons, aluminium is considered for the production of bridge decks made of multi-cellular extrusions welded together. Decks are to be connected to steel girders with slip-critical bolted joints, in order to achieve composite action between the deck and the girders. The main concern is the lack of accessibility of the interior of the extrusions. This prevents the setting up of the slip-critical bolteds joints, compliantly with the canadian standards about highway bridges. Two solutions are studied : the use of blind bolts and the design of an special extrusion to join the deck to the beams. For each of these solutions, a feasability study is led. Two models of blind bolts are identified, then modeled by finite elements to determine wether they match the CAN/CSA-S6-2014 requirements about slip-critical joints. The solutions explored in this project are finally campared by the mean of SWOT analysis, in order to bring out their strenghts, weaknesses, opportunities and threats. Key-words 6063-T6, aluminium, blind bolt, bridge, CAN/CSA-S6-2014, deck, extrusions, finite elements slip-critical joint.
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Pratapa, Suminar. "Synthesis and character of a functionally-graded aluminium titanate/zirconia-alumina composite." Curtin University of Technology, Department of Applied Physics, 1997. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14696.
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A functionally-graded Al(subscript)2TiO(subscript)5/ZrO(subscript)2-Al(subscript)2O(subscript)3 (AT/zirconia-alumina) composite has been successfully synthesized by an infiltration process involving an alpha-Al(subscript)2O(subscript)3-ZrO(subscript)2 (90:10 by weight) green body and a solution containing titanium chloride. The mass gain after infiltration has been used to estimate the amount of new phase introduced into the system. The phase composition character of the functionally-graded material (FGM) has been determined by x-ray diffraction. The Rietveld "whole pattern" refinement method was applied to diffraction patterns of the sample which were collected from the surface and at several depths which were made by polishing away the material. Absolute weight fraction determination using the Rietveld external standard method showed that the concentration of AT reduces linearly from the surface to the core. In contrast, the alpha-alumina content increases with depth in a complementary manner. Low level amorphous phase was also observed. Other functionally-graded microstructural profiles examined were x-ray characteristic line intensity of Ti, Ti dot-mapping, and alpha-alumina grain size. The FGM also exhibits graded character in both thermal and mechanical properties, i.e. thermal expansion, microhardness, and Young's modulus. The thermal expansion coefficient (TEC) of the FGM increased with polishing-depth and approached that of the zirconia-alumina reference sample at a depth of 0.5 mm.Relatively lower thermal expansion and softer surface layer in comparison to those of the core (TEC value of 5.9 x 10(subscript)-6 degrees celsius(subscript)-1 and microhardness of 6 GPa compared to 7.4 x 10(subscript)-6 degrees celsius(subscript)-1 and 12 GPa, respectively) render possibilities to implement the material to which thermal shock resistance surface but hard core, such as a metal melting crucible, are required. Load-dependent microhardness was obviously observed on the surface of the material but only slight dependence was observed in the core. This observation indicated that the material exhibit "quasi-ductile" surface but brittle core. In comparison to the reference specimen, the FGM displayed damage-tolerance and remarkable machinability.
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Qian, Daishu. "Microstructure and corrosion performance of excimer laser-melted AA2124-T4 aluminium alloy and SiCp/AA2124-T4 composite." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/microstructure-and-corrosion-performance-of-excimer-lasermelted-aa2124t4-aluminium-alloy-and-sicpaa2124t4-composite(705f8af9-2a7c-4188-91e4-fcf33d8f76f0).html.
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The present work studies the microstructure and corrosion behaviour of 25 vol.% SiCp/AA2124-T4 metal matrix composites (MMCs) and AA2124-T4 aluminium alloy; and also the capability of excimer laser surface melting (LSM) to improve the corrosion resistance of the SiCp/AA2124 MMC and the monolithic alloy (MA). Microstructural characterization has shown significant influence of the presence and size of SiC particles on the fine Al2Cu precipitate and Mg segregation at SiC/Al interfacial regions. Such precipitates are revealed to be active sites for corrosion initiation in the MMCs, while the preferential sites for corrosion initiation in the MA are the coarse intermetallics. Corrosion evaluation performed in a 0.6 M NaCl solution suggests that the corrosion resistance of the MMC reinforced with micrometre-sized SiC particles is inferior to that of the MA and the MMC reinforced with submicrometre-sized SiC particles. The submicrometre-sized SiC particles have little adverse effect on the corrosion resistance of the MMC due to the reduced interfacial precipitates. Thin films of up to several micrometres have been achieved by excimer LSM on both the MMC and the MA. The surface roughness and the thickness of the melted layer increase with increasing laser fluence. High number of pulses (40 P) results in significant porosity in the MA and networks of cracking in the MMC. A homogeneous layer without chemical segregation except the Cu-rich segregation bands has been obtained on the MA; while complex microstructures are observed for the MMC, including the Cu-rich segregation bands, Al-Si eutectic structure and microsegregation-free structure laid in sequence from the bottom of the melted layer to the top surface. The modelling work suggest that the presence of SiC particles gives rise in high temperatures in the melt pool, which is useful to explain the materials responses upon laser irradiation, such as decomposition of SiC, evaporation of matrix alloy, and oxides formation. The fast cooling rate up to 1011 K/s is responsible for the formation of microsegregation-free structure. Corrosion evaluation has indicated improvement of corrosion resistance of the MMC and the MA after excimer LSM due to the reduction of the intermetallics. For the laser-melted MA, the corrosion behaviour is governed by the surface morphology and the porosity. The significant rippled structure obtained under high laser fluence could lead to crevice corrosion in the valley between the ripples whilst the pores could provide penetrating routes for the chloride solution to reach the Cu-rich segregation bands, leading to the delamination of the melted layer. For the laser-melted MMC, corrosion mainly initiated at the SiC remnants, which are rich in Si. The corrosion sites of the laser-melted MMC are in the form of small cracked blisters.
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Cano-Castillo, U. "Environment-assisted cracking of spray-formed Al-alloy and Al-alloy-based composite." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260730.
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Sparks, Christopher Nigel. "Hot formability and microstructural development of spray-deposited Al-Li alloy and composite." Thesis, University of Sheffield, 1994. http://etheses.whiterose.ac.uk/1805/.
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The deformational and microstructural behaviour of the commercial Al-Li alloy 8090 and an 8090 based composite containing silicon carbide particulate has been investigated. The materials were deformed at elevated temperature by the test methods of plane strain compression (PSC) and torsion to provide stress-strain data for the formulation of constitutive relationships. Torsion testing also provided high temperature ductility data. Isothermal annealing of rolled samples was carried out at the solution temperature of 530°C to investigate the recrystallisation kinetics and microstructures produced, with particular emphasis on the effect of the inclusion of reinforcement particles on the behaviour of the matrix alloy. Hyperbolic sine forms of constitutive equation have been produced and are found to provide good agreement with the experimental data. High values of the activation energy are calculated for the deformation of both the alloy and composite from the PSC test data. The equations obtained from the two different test methods are found to be comparable for the composite material, but a discrepancy is found for the monolithic alloy, where apparently less hardening results from torsion testing. A distinct transition in microstructure from recrystallised equiaxed grains when deformed at low temperature to an elongated, sometimes partially recrystallised, structure for material rolled at high temperature is present in the monolithic material. This is attributed to the balance of recrystallisation driving force and the Zener pinning force exerted by the 13' (A1 3Zr) phase. The composite material exhibited greatly enhanced recrystallisation kinetics in agreement with the theory of particle stimulated nucleation (PSN) of recrystallisation.
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Briskham, Paul Graham. "Strong and durable fusion bonding of glass reinforced polypropylene to pretreated aluminium." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342549.
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Smith, Joel Edmund. "Development of improved metal matrix composite via the control of interface and matrix microstructure." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296330.
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Peng, Tao. "Processing and characterization of multi-walled carbon nanotube reinforced aluminium metal matrix composite." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6593/.
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Aluminium(Al) is widely utilised in the packaging, transportation, electrical and modern machinery sections because of its low density, high specific strength, excellent corrosion resistance, impressive electrical and thermal conductivity, abundance and recyclability. However, relatively low strength is the most significant challenge for aluminium to be applied in wider area. To solve this problem, carbon nanotube was projected as the most ideal reinforcement due to its incomparable specific strength and elastic modulus, exceptional electrical and thermal conductivity. It is assumed that carbon nanotube can not only strengthen but also introduce various distinctive characteristics into the aluminium matrix to improve its overall properties and performances. In the current research, 0.5 wt. % – 2.0 wt. % of mutil-walled carbon nanotube was ball milled with aluminium powders for 5 – 20h. The microstructure of the as-milled composite powders and as-sintered bulk composite specimens were characterized by particle size analysis, optical microscopy and scanning electron microscopy(SEM). Also, the evolution and dispersion of MWNT were studied by Raman spectroscopy and SEM. Moreover, the as-produced composites were subjected to standard Vickers hardness test and MPIF standard tensile test to investigate the mechanical properties of the composite.
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Kapidzic, Zlatan. "Static and Fatigue Failure of Bolted Joints in Hybrid Composite-Aluminium Aircraft Structures." Doctoral thesis, Linköpings universitet, Mekanik och hållfasthetslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-122349.
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The use of fibre composites in the design of load carrying aircraft structures has been increasing over the last few decades. At the same time, aluminium alloys are still present in many structural parts, which has led to an increase of the number of hybrid composite-aluminium structures. Often, these materials are joined at their interface by bolted connections. Due to their different response to thermal, mechanical and environmental impact, the composite and the aluminium alloy parts are subject to different design and certification practices and are therefore considered separately.The current methodologies used in the aircraft industry lack well-developed methods to account for the effects of the mismatch of material properties at the interface.One such effect is the thermally induced load which arises at elevated temperature due to the different thermal expansion properties of the constituent materials. With a growing number of hybrid structures, these matters need to be addressed. The rapid growth of computational power and development of simulation tools in recent years have made it possible to evaluate the material and structural response of hybrid structures without having to entirely rely on complex and expensive testing procedures.However, as the failure process of composite materials is not entirely understood, further research efforts are needed in order to develop reliable material models for the existing simulation tools. The work presented in this dissertation involves modelling and testing of bolted joints in hybrid composite-aluminium structures.The main focus is directed towards understanding the failure behaviour of the composite material under static and fatigue loading, and how to include this behaviour in large scale models of a typical bolted airframe structure in an efficient way. In addition to that, the influence of thermally induced loads on the strength and fatigue life is evaluated in order to establish a design strategy that can be used in the industrial context. The dissertation is divided into two parts. In the first one, the background and the theory are presented while the second one consists of five scientific papers.
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Ison, Stephen John. "Interfacial reactions between PbO-rich glasses and aluminium composites." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364605.
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Dan, Chengyi. "Effects of nanoparticles on the microstructure and crystallographic texture evolution of two Aluminium-based alloys." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS147.
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Les effets des nanoparticules (cisaillables et non-cisaillables) sur l’évolution microstructurale et l'évolution de la texture cristallographique des deux alliages à base d’aluminium après laminage à froid ont été étudiés dans cette thèse. Un alliage Al-Sc contenant des nanoparticules cisaillables de Al3Sc et un composite Al-TiB2 contenant des nanoparticules non-cisaillables TiB2 sont étudiés. La microscopie électronique en transmission (MET), la diffraction d'électrons rétrodiffusés (EBSD) et l’analyse de la texture par la diffraction de neutrons sont utilisées pour caractériser le développement de la microstructure et la texture cristallographique lors du laminage à froid des 2 alliages.La restauration dynamique pendant laminage a été inhibée dans la matrice contenant des Al3Sc nanoparticules cisaillables et TiB2 non-cisaillables. Par conséquent, peu de cellules de dislocation ont été générées dans la matrice, ce qui limite la diminution de la taille des grains.Le développement de la texture de laminage est retardé par les nanoparticules cisaillables ou les particules non-cisaillables. Des bandes d’orientation de cube résiduelles se trouvent dans les matériaux contenant des particules cisaillables dans une matrice très déformée en raison de la limitation du glissement croisé. La réduction de la proption volumique des composantes de texture du laminage se produit dans les matériaux contenant de grandes particules non-cisaillables (de l’ordre d’un micromètre) en raison de la recristallisation dans les PDZs (Particle Deformation Zones), ce qui contribue également à la diminution des grains.De plus, le cisaillement de nanoparticules favorise le glissades en plan, ce qui conduit à une forte localisation des déformations et à l'apparition de bandes de cisaillement. La génération de bandes de cisaillement dépend de l'orientation et est dû au changement soudain des chemins de déformation et et de l'inhibition de la récupération dynamique. Les nanoparticules non cisaillables ont probablement pivoté avec la matrice environnante, ce qui pourrait constituer un nouveau mécanisme de déformationThe effects of shearable and non-shearable nanoparticles on the microstructure and crystallographic texture evolution of two Al-based alloys after cold rolling have been studied in this thesis. An Al-Sc alloy containing shearable Al3Sc nanoprecipitates and Al-TiB2 composite containing non-shearable TiB2 nanoparticles are investigated, respectively. Transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and neutron diffraction texture analysis are employed to characterize the microstructure and texture development of the two alloys during cold rolling.Dynamic recovery has been inhibited in the matrix containing both shearable (Al3Sc) and non-shearable (TiB2) nanoparticles due to the pinning effects. Hence, few dislocation cells are generated in these matrices that impedes the grain refinement.The development of rolling texture is retarded by either shearable nanoprecipitates or non-shearbale particles. Obvious residual Cube orientation bands are found in materials containing shearable precipitates at the deformed states due to the limitation of cross-slip. Volume reduction of rolling texture components occurs in materials containing large non-shearable particles (about 1 micrometer) due to the recrystallization at PDZs (Particle Deformation Zones), which contributes to grain refinement.In addition, the shearing of nanoprecipitates promotes planar slip leading to strong strain localization and the occurrence of shearbands. The generation of shearbands is orientation dependent and results from the sudden change of deformation paths and inhibition of dynamic recovery. The non-shearable nanoparticles probably have rotated together with the surrounding matrix, which could be a new deformation mechanism
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Segovia, Abanto Franz. "Développement d'un matériau composite à base de bois laminé avec alliage d'aluminium." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/29810.
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Les matériaux composites sont constitués d’au moins deux matériaux dont les propriétés individuelles se combinent pour former un matériau hétérogène ayant des performances globales fortement améliorées. Parmi les types de matériaux composites, on retrouve les matériaux composites à structure sandwich, lesquels consistent en l’assemblage par collage ou soudure de deux revêtements ou peaux minces, faits d’un matériau rigide et lourd, sur un noyau épais et léger qui maintient leur écartement. Les principaux bénéfices de ces structures sont: la légèreté, la très grande rigidité, la grande résistance en flexion et l’isolation thermique. La combinaison des propriétés des matériaux utilisés comme revêtement et noyau procure aux matériaux composites à structure sandwich plusieurs avantages mécaniques, environnementaux et économiques, permettant ainsi l’élargissement du potentiel de ces matériaux composites à différentes applications. L’objectif général de ce projet de doctorat était de développer un matériau composite à base de bois laminé avec alliage d’aluminium. Les objectifs spécifiques de ce projet de recherche étaient de déterminer les propriétés physiques et mécaniques, d’estimer les coûts de production et de mesurer la performance environnementale des matériaux composites à structure sandwich. Finalement, des applications potentielles étaient évaluées en utilisant la recherche qualitative comme méthodologie. Des matériaux à structure sandwich ont été développés en utilisant quatre types de matériaux composites à base de bois (panneau de fibres à haute densité, panneau de fibres à densité moyenne, panneau de lamelles orientées et contreplaqué) comme noyau, alors qu’un alliage d’aluminium 3003 a été utilisé comme peau ou revêtement. Un adhésif polyuréthane (Macroplast UR-8346) a été utilisé pour coller les composants du matériau composite. Les paramètres de fabrication ont été déterminés à travers des essais préalables. Les propriétés physiques des matériaux composites à base de bois ont été améliorées par le laminage avec l’alliage d’aluminium. Les propriétés mécaniques en flexion, comme le module d’élasticité apparent (Eapp) et le module de rupture (MOR), ont été significativement augmentées avec le laminage d’alliage d’aluminium. L’estimation des coûts de production du matériau composite développé nous a permis de démontrer un avantage économique par rapport au panneau nid d’abeille en aluminium. La comparaison de la fabrication des matériaux composites laminés avec alliage d’aluminium par rapport au panneau nid d’abeille en aluminium a permis d’identifier les avantages environnementaux de l’utilisation des matériaux composites à base de bois comme noyau. L’analyse de l’impact environnemental (IMPACT 2002+) a montré que les émissions associées à la fabrication de tôles d'aluminium se sont avérées les plus grandes contributrices aux impacts environnementaux globaux de la fabrication des matériaux composites à structure sandwich développés. Les avantages techniques, économiques et environnementaux des matériaux composites laminés avec alliage d’aluminium ont multiplié ses applications potentielles. Enfin, la recherche qualitative basée sur la théorie ancrée a permis de déterminer les principales applications possibles à partir des suggestions des personnes interviewées. L’utilisation du Logiciel Nvivo 11 de QRS international a permis le codage des principales catégories. Les principales applications suggérées par les personnes interviewées ont été l’utilisation pour les planchers surélevés; l'application comme diviseurs de salle de bain et l’application comme panneau de contreventement ou panneau décoratif.Composite materials consist of at least two materials whose individual properties combine to form a heterogeneous material with greatly improved overall performance. Among the types of composite materials are laminated panels or sandwich panels. These consist in the assembly by bonding or welding of two thin skins, made of a rigid and heavy material, on a thick and light core which maintains their spacing. The main benefits of these structures are: lightness, high rigidity, high flexural strength, and thermal insulation. The combination of materials used as faces and core provides laminated panels with several mechanical advantages as well as environmental and economic benefits. Consequently, the potential applications of these composite materials are extended. The overall objective of this doctoral project was to develop a wood-aluminum laminated panel. The specific objectives of this research project were: to determine physical and mechanical properties; to estimate production costs; and to verify the environmental performance of wood-aluminum laminated panels. Finally, potential applications were proposed using qualitative research methodology. Wood-aluminum laminated panel has been developed using four types of wood-based composite as core (high density fibreboard, medium density fibreboard, oriented strand board, and aspen plywood) and two 0.6-mm-thick aluminum alloy sheets as faces. The polyurethane adhesive (Macroplast UR-8346) was used to bonding laminated panels. The manufacturing parameters were determined through prior testing. The physical and mechanical properties of wood-based composites have been improved by lamination with aluminum alloy sheets. The production costs estimate concluded that the developed laminated panels have an economic advantage over the aluminum honeycomb panel. The manufacturing process of laminated composite materials with aluminum alloy shows lower environmental impacts compared to aluminum honeycomb panel. Emissions associated with the manufacturing process of aluminum sheets is the largest contributor to environmental impacts in sandwich composite materials manufacturing. The technical, economic and environmental benefits have extended the potential applications of wood-based composite materials. Qualitative research based on the grounded theory approach was used to determine the main potential applications. The main applications suggested by the interviewees were: raised flooring panels, bathroom dividers panels and decorative and bracing panels.
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Perron, Christophe. "Définition et mise en oeuvre d'un matériau composite à matrice métallique pour les packagings d'électronique embarquée." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0646/document.
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Les packagings d’électronique embarquée sont actuellement en alliages d’aluminium. A partir d’une étude de sélection des matériaux, complétée par une simulation numérique thermique,nous avons démontré qu’un matériau composite constitué d’une matrice aluminium et de fibres de carbone à forte conductivité thermique, représente un fort potentiel de gain de masse sur ces équipements. Cependant, le couplage de ces deux matériaux génère des problèmes d’élaboration en raison d’incompatibilités fortes parmi lesquelles un mouillage très faible du carbone par l’aluminium liquide et une réactivité chimique élevée qui conduit à la formation de carbures d’aluminium préjudiciables pour le matériau final. Deux voies d’élaboration distinctes ont été envisagées : Une voie liquide où l’utilisation d’un agent de mouillage (un sel fluoré) a permis d’obtenir la montée par capillarité du métal dans des mèches de fibres. Une voie solide basée sur une technique originale d’empilements de feuillets d’aluminium et de fibres de carbone avec le procédé de Spark Plasma Sintering (SPS). .La seconde technique s’est révélée prometteuse en permettant d’obtenir des échantillons multicouches sans porosités, un endommagement très limité des fibres et une architecture contrôlée.Notre étude a montré que la formation de carbures d’aluminium est limitée. De plus, une meilleure compréhension du SPS ou l’application d’un revêtement sur les fibres devraient permettre d’éviter la formation de ces carbures. Les tentatives de caractérisations mécanique et thermique effectuées sur ces échantillons donnent un premier aperçu de l’efficacité du renforcement de l’aluminium par les fibres de carboneEmbedded electronic packagings are currently made of aluminum. A first study – basedupon a material selection method completed by numerical analysis – showed that a metal matrixcomposite made of aluminum and highly thermal conductive continuous carbon fibers represents ahigh potential upon weight savings for those equipments. Though, coupling these componentsrepresents numerous challenges due to their incompatibility such as a really low wetting of carbonliquidaluminum system and its unavoidable chemical reactivity that leads to the formation ofaluminum carbides that are harmful for the final material. Two manufacturing routes were considered: A liquid route using a wetting agent (fluorinated salts) led the metal to rise alongcarbon fibers by capillarity. A solid route based upon a novel technique of aluminum foils and carbon fibersstacking using the Spark Plasma Sintering (SPS) process.This second technique revealed to be very promising and allowed to obtain multilayer samples with noporosities, highly limited fiber damages and controlled composite architecture. Our study shows thataluminum carbides formation is limited. Moreover, a deeper comprehension of SPS process or thedeposit of fiber coatings would prevent this carbide formation. Attempts of mechanical and thermalcharacterization led upon such samples give a first overview of the efficiency of the aluminumreinforcement by carbon fibers
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Hayes, Ian. "Microstructural characterisation and heat treatment refinement of a particulate reinforced aluminium metal matrix composite." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8077/.
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The purpose of this work was to determine the microstructure and secondary phase distribution in the TiB2 particulate reinforced Al-4.5Cu A205 alloy. This was extended to sand, investment and die casting techniques with the overall aim of optimising the existing solution heat treatment protocol for a variety of possible starting conditions. Additional work was aimed at determining a relationship between TiB2 additions and the observed globular microstructure. Hardness testing, DSC analysis, EDS and tensile testing were used to determine the effectiveness of heat treatment. It was found that a 4hr solution treatment at 538oC did not produce significantly different results from a 44hr, four step treatment process. As the diffusion behaviour of Cu was judged to be the most important factor affecting solution heat treatment, a simple microstructural model of typical A205 grain structures was proposed. The model was found to operate on similar timescales to those observed from experimental testing of A205 but was limited by idealised phase structures. The castability of A205 was determined using fluidity and hot tearing experiments. The better than expected castability was attributed to enhanced feeding brought about by the globular structure of A205.
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McCague, Colum. "Development of novel composite cement systems for the encapsulation of aluminium from nuclear wastes." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678940.
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Currently in the UK, composite blends of Portland cement (PC) and blastfurnace slag (up to 90%) are commonly used for the encapsulation of low and intermediate level wastes. The high volume replacement of PC is considered necessary in order to to reduce the high heat generation resulting from cement hydration in 500 litre waste packages. While suited to the majority of waste streams, the high pH environment in such systems (usually around 12.5 -13), will cause the corrosion of certain waste metals such as aluminium. Since aluminium is only passive between pH4 - 8.5, the use of an alternative low-pH cement system could serve to reduce/inhibit the corrosion. However, before such cements can be considered, two main research problems must be addressed, as follows: (1) quantitative evaluation of alternative cement systems based on their corrosion performance with aluminium; (2) high heat generation due to the rapid rate of hydration. The research in this thesis was thus divided into two strands, as follows: (1) The design and development of a novel, scientifically robust testing facility for the quantitative monitoring of aluminium corrosion in cement pastes; (2) the development of novel cement composites based on weakly alkaline calcium sulfoaluminate (CSA) cement for the encapsulation of aluminium from nuclear wastes. The output from this research is considered to be of interest to the UK nuclear industry.
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Ribes, Hervé. "Microstructure de composites aluminium-carbure de silicium après traitements thermomécaniques." Grenoble INPG, 1989. http://www.theses.fr/1989INPG0084.
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Ce travail porte sur l'etude de composites a matrices aluminium (al-mg-si) renforcees par des particules de carbure de silicium qui ont ete utilisees soit brut de reception soit prealablement oxydees. Une investigation microstructurale detaillee (realisee en partie par microscopie electronique en transmission) a permis de preciser la nature de l'interface al/sic dans ces composites ainsi que l'evolution de la precipitation apres traitements thermiques. Nous avons montre que l'interface est souvent composee par differentes interphases dont la composition et le mode de formation sont presentes. Nous montrons alors que la nature de l'interface modifie les proprietes mecaniques et en particulier l'allongement a rupture. A partir de l'etude de la precipitation et d'essais de durete, nous montrons qu'il est necessaire d'optimiser les conditions de traitements thermiques dans les composites. Ainsi en modifiant les interfaces, en optimisant la composition de la matrice et les traitements thermiques dans les composites. Ainsi en modifiant les interfaces, en optimisant la composition de la matrice et les traitements thermiques il doit etre possible d'obtenir une nouvelle generation de composites
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Coelho, Reginaldo Teixeira. "The machinability of aluminium-based SiC reinforced metal matrix composite (MMC) alloy with emphasis on hole production." Thesis, University of Birmingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340966.
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Zhu, Yubin. "Etude de l'interface d'un composite à matrice à base de Ti-Al." Paris 11, 2001. http://www.theses.fr/2001PA112362.
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Mendes, Luís Gonçalves. "Production of aluminium based composites reinforced with embedded NiTi by friction stir welding." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/8764.
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Dissertação para a obtenção do grau de Mestre em Engenharia MecânicaAluminium alloys have been widely used in composite materials in order to promote an enhancement in its properties while reducing weight. As in the production of new composites with a significant difference in mechanical and thermo-physical properties fusion welding processes enhances the formation of undesired intermetallics. Those limitations have driven research on solid state technologies, such as Friction Stir Welding (FSW), for joining dissimilar materials. This study aimed to develop composites in AA 1XXX series aluminium alloys with NiTi by FSW. Different reinforcing material shapes were investigated, analyzed the interfaces and the resulting material flow. The final product was mechanically characterized. It was observed an increase of 70 % of ultimate tensile strength, compared to Al base material and yielding between the two dissimilar materials was greater than the Al lap joint yield stress. The final composite depicted a good electrical conductivity, reducing less than 3 % IACS of the Al base material. Thus, a composite with a strong mechanical bonding was produced, maintaining the original functional properties of the reinforcement NiTi alloy, and the electrical properties of the Aluminium.
FCT/MCTES - "Desenvolvimento da tecnologia de processamento por fricção linear para produzir materiais com gradiente de funcionalidade e melhoria de superfícies para aplicações avançadas de engenharia – FRISURF"
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Lalet, Grégory. "Composites aluminium/fibres de carbone pour l'électronique de puissance." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00538480.
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L'étude a pour objectif l'amélioration de la fiabilité des assemblages électroniques à travers la mise en œuvre de drains composites aluminium/fibres de carbone. Le travail a consisté à 1) modéliser, par la méthode des éléments finis, l'influence des propriétés thermiques et mécaniques du matériau de semelle sur l'assemblage életronique ; 2) élaborer (par frittage sous charge uniaxiale, frittage flash et extrusion à chaud) des matériaux composites aluminium/fibres de carbone ; et 3) lier les microstructures observées aux paramètres des procédés d'élaboration ainsi qu'aux propriétés thermiques et mécaniques mesurées.
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Troadec, Carole. "Composite à matrice métallique Al-AlN : de la poudre au matériau." Grenoble INPG, 1996. http://www.theses.fr/1996INPG4205.
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Cette etude s'inscrit dans le cadre de l'elaboration de composites a matrice metallique aluminium/nitrure d'aluminium, par metallurgie des poudres. Deux types de poudres sont utilisees: une poudre dite composite synthetisee par nitruration directe de l'aluminium par l'azote et une poudre dite melange obtenue a partir d'un melange de poudres commerciales elementaires aluminium et nitrure d'aluminium. Ces deux types de poudres subissent un broyage hautement energetique par melangeur planetaire sous argon, puis sont frittes par compression a chaud en phase solide. La microstructure de ces materiaux, etudiee en met et nanoanalyse edx, est relativement heterogene, constituee de zones denses polycristallines et de zones a forte porosite constituees de nanocristaux. La taille de ces zones microporeuses est superieure dans les materiaux melanges et varie en fonction du taux de nitrure d'aluminium et du temps de broyage. Les zones denses sont composees de grains d'aluminium entoures de nanocristaux de nitrure d'aluminium, avec des aiguilles d'alumine et quelques cristaux d'oxynitrure d'aluminium. L'ordre de grandeur des cristaux (<1 m) est confirme par diffraction des rayons x. Les proprietes physico-chimiques (coefficient de dilatation, conductivites thermique et electrique) et mecaniques (durete, module de young, limite d'elasticite, contrainte a la rupture) different en fonction du type des poudres de depart et evoluent avec la teneur en aln. Le comportement des deux types de materiaux differe egalement en usure et en corrosion. Ces nouveaux materiaux ont dans l'ensemble, a teneur en renfort similaire, des proprietes equivalentes a celles des materiaux al/sic ou al/al#2o#3
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Amiriyan, Mahdi. "Development of ceramic reinforced iron aluminide based composite coatings for wear resistant applications." Doctoral thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/35012.
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Les composés intermétalliques Fe₃Al et leurs revêtements composites sont des matériaux structuraux potentiels pour des applications tribologiques. Parmi les composites, ceux obtenus par broyage mécanique à haute énergie possèdent plusieurs avantages, en particulier une fabrication rentable. Le broyage à billes à haute énergie permet également une large gamme de fraction volumique des particules de renforcement. Dans cette recherche, Nous avons préparé des revêtements composites à matrice d'aluminiure de fer, basés sur la composition chimique de Fe₃Al avec des particules de renforcement de TiC et de TiB₂ en utilisant un broyeur à billes à haute énergie et déposé par la technique HVOF (High Velocity Oxy Fuel). L'effet des paramètres de traitement tels que la durée du broyage et le traitement thermique subséquent sur les la matière première destinés à la projection par HVOF a été étudié. Les paramètres de traitement ont joué des rôles importants sur la poudre composite et par la suite sur la microstructure, les propriétés mécaniques et tribologiques des revêtements. Le but de la première phase expérimentale de ce travail était d'étudier l'effet des particules de TiC in situ sur la microstructure, le comportement mécanique et tribologique des revêtements de Fe₃Al déposés par HVOF. Dans cette étape, des poudres composites Fe₃Al / TiC avec différentes quantités de carbure de titane ont été produites par broyage à haute énergie. Un mélange de Fe₃Al-Ti-C a été broyé pendant 6 h suivi d'un traitement thermique à 1000 °C pendant 2 h sous vide poussé. Des revêtements composites d'aluminure de fer renforcés au TiC in situ ont été préparés pour améliorer la dureté Vickers et la résistance à l'usure des intermétalliques de Fe₃Al. Les revêtements composites consistent principalement en une phase de TiC uniformément dispersée dans des lamelles de la matrice de Fe₃Al. Les revêtements composites ont montré une dureté Vickers croissante avec l’augmentation de la quantité de TiC, allant jusqu'à 70 % en moles de TiC. La résistance à l'usure par glissement à sec des revêtements a été augmentée avec l'addition de particules de TiC formées in situ. Les revêtements composites de Fe₃Al déposés par HVOF avec des renforts en TiC de 50 % et 70 % en moles présentaient une excellente résistance à l'usure par glissement. Le mécanisme d'usure dominant de ces revêtements était l'abrasion et l'oxydation. Dans une autre étape de ce travail, des poudres composites de Fe₃Al-TiB₂ avec deux quantités différentes de borure ont été produites par le dépôt par high Velocity Oxy Fuel (HVOF) sur un substrat en acier. Les revêtements composites consistaient principalement en une phase de TiB₂ pré-synthétisée et uniformément dispersée dans des lamelles de la matrice de Fe₃Al. Il a été montré qu'en augmentant la fraction volumique du TiB₂, la dureté Vickers et la résistance à l'usure par glissement des revêtements contre le contre-corps en alumine (6,33 mm de diamètre) étaient augmentées. L'augmentation de la résistance à l'usure était censée être liée à l'amélioration de la dureté, qui à son tour est due à la présence de particules de TiB₂ dans la matrice Fe₃Al. Le taux d'usure de glissement des revêtements a augmenté pour atteindre un maximum lorsque la vitesse de glissement augmente, puis il a diminué avec l'augmentation supplémentaire de la vitesse de glissement. Les analyses chimiques des surfaces usées ont montré que des vitesses de glissement plus élevées entraînent une oxydation plus élevée de la surface, probablement en raison de la température locale plus élevée. Une telle couche d'oxyde semble agir comme une barrière entre deux corps coulissants, diminuant ainsi le taux d'usure.Fe₃Al intermetallic compounds and their composite coatings are potential structural materials for tribological applications. High-energy ball milled powders possess several advantages, especially cost-effective fabrication and lower cost of reinforcement. High-energy ball mill also allows for a wide range of reinforcement volume fraction. In this research, Iron Aluminide matrix composite coatings based on Fe₃Al chemical composition with TiC and TiB₂ particles were prepared using a high-energy ball mill and deposited via the High Velocity Oxy Fuel (HVOF) technique. The effect of processing parameters such as ball milling duration and subsequent heat treatment soaking time and temperature on the phases of products as a feed stock for the HVOF gun was studied. The processing parameters played important roles on the microstructure, mechanical and tribological properties of the coatings. The aim of the first experimental stage of this work was to study the effect of in-situ TiC particles on microstructure, mechanical and tribological behavior of HVOF deposited Fe₃Al coatings. In this stage Fe₃Al/TiC composite powders with different carbide quantities were produced via high-energy ball milling of Fe₃Al-Ti-C system for 6 h followed by heat treatment at 1000 °C for 2 h under high vacuum. In-situ TiC-reinforced iron aluminide composite coatings were prepared to improve the Vickers hardness and wear resistance of Fe₃Al intermetallics. The composite coatings mainly consist of a TiC phase uniformly dispersed within lamellae of the Fe₃Al matrix. The composite coatings showed increasing Vickers hardness with increasing TiC content up to 70 mol% TiC. The dry sliding wear resistance of coatings was increased with the addition of in-situ formed TiC particles. HVOF deposited Fe₃Al composite coatings with 50 and 70 mol% TiC reinforcements exhibited excellent sliding wear resistance. The dominant wear mechanism in those coatings was abrasion and oxidation. In another stage of this work Fe₃Al-TiB2 composite powders with two different boride quantities were produced by the high Velocity Oxy Fuel (HVOF) spray deposition on a steel substrate. The composite coatings mainly consisted of a TiB₂ phase uniformly dispersed within lamellae of the Fe₃Al matrix. It was shown that by increasing the volume fraction of TiB₂ both the Vickers hardness and sliding wear resistance of the coatings against alumina counterbody (6.33 mm in diameter) were increased. The increase of wear resistance was believed to be related to the hardness enhancement, which, in turn, is due to the presence of TiB₂ particles within the Fe3Al matrix. The sliding wear rate of the coatings increased to reach a maximum as the sliding speed increases, and then it decreased with further increase of the sliding speed. The chemical analyses of the worn surfaces showed that higher sliding speeds result in higher oxidation of the surface, most likely due to the higher local temperature. Such an oxide layer seems to act as a barrier between two sliding bodies, thus decreasing the wear rate.
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LE, PEN ERIC. "Approche micromecanique du comportement en fatigue d'un materiau composite a matrice aluminium renforce par fibres d'alumine." Paris, ENSAM, 1999. http://www.theses.fr/1999ENAM0019.
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Dans le but de prevoir le comportement en fatigue de materiaux composites a matrice metallique, une approche micromecanique de type mori&tanaka a ete developpee. La microstructure est definie precisement par observations fines et analyse d'images : on distingue dans le cas general une matrice ductile ainsi que des particules ou des fibres distribuees en familles d'orientations. D'autre part la mise en place de moyens d'essais de fatigue sur mini-eprouvettes permet d'identifier les mecanismes d'endommagement au cours des cycles. Les parametres d'ecrouissage de la matrice sont egalement determines experimentalement et permettent d'alimenter le modele micromecanique. Ce modele est fonde sur une theorie en champs de contraintes et deformations moyennes pour chaque constituant. Le chargement est impose de maniere incrementale et le passage micro-macro s'effectue par l'intermediaire des modules tangents. On peut ainsi reproduire des trajets de chargement complexes incluant des decharges. Le comportement global du composite est alors regit par les caracteristiques mecaniques et geometriques a l'echelle locale. Les equations de plasticite sont resolues dans la matrice et satisfont une loi d'ecrouissage phenomenologique faisant intervenir les variables internes. Il est possible de rendre compte des phenomenes d'adoucissement ou de durcissement cyclique. Dans le cas d'un composite a matrice aluminium as7g03 renforce par fibres d'alumine et elabore en squeeze-casting le modele prevoit des reponses en fatigue oligocyclique proches de l'experience. Pour prevoir le comportement a plus grand nombre de cycles, les phenomenes d'endommagement tels qu'observes experimentalement au meb ont ete integres. L'evolution statistique de la population de fibres combinee aux phenomenes de fermeture et re-ouverture, permet finalement de prevoir le comportement global du composite au cours des cycles.
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MAKUNTUALA, KEVA. "Desenvolvimento de compositos refratarios SiC-AlN e SiC-SiAlON." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9274.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Jammula, Chaitanya Krishna. "Correlating the microstructure with wear properties of aluminium silicon carbides." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Industriell produktutveckling, produktion och design, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-45820.
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Aluminium is one of the metals playing a prominent role in automobile industry after cast iron. Because of its light weight property and good mechanical properties. When aluminium reinforced with silicon carbide showing good tribological properties and improved strength. Aluminium silicon carbide needs some good wear and frictional properties to use it as break disc. Aluminium reinforced with 15% and 20% silicon carbide and casted in two different ways, liquid casting and stir casting. Four different composites are compared in this paper. Hardness test was carried out on the samples. Increase in the Vickers hardness with increase in silicon carbide reinforcement for both the castings is observed. Rockwell C hardness is showing decreasing trend with increase in SiC reinforcement. The scratch resistance of the surface under micro level was analysed with the help of nano scratch test. The SiC particles in the aluminium matrix are resisting the indenter from deep deformation of the surface. Frictional forces are dropped whenever the indenter met the SiC particles. In other cases, SiC particles are deforming the aluminium matrix in the form of broken particles. The plastic deformation of aluminium is observed, and material is piled up on sideways of groove at high load.Sliding wear behaviour of the composites are investigated by means of reciprocating pin on plate wear rig. The test was carried out at load of 20N for five different sliding duration. Aluminium with 20% silicon carbide of liquid casting is used as a base metal. The worn-out surface of the samples is analysed in SEM. The metallography of the worn-out samples is showing some deep grooves and abrasion of the material. Wear debris from both the surfaces are forming into a cluster of layers. These layers are protecting the surface from wear in some areas were observed. Composition of tribo layer formed during the test was investigated with the help of EDS analysis. The tribo layer are rich in aluminium and silicon elements because both the samples are made of aluminium silicon carbide.
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Pastor, Marie-Laetitia. "Contribution à l'étude en fatigue de structures en aluminium renforcées par patchs composites." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2007. http://tel.archives-ouvertes.fr/tel-00204550.
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Les composants aéronautiques sont soumis en service à des sollicitations mécaniques donnant lieu à des états de contraintes multiaxiaux et à amplitude variable provocant un phénomène d'endommagement par fatigue. Une alternative à la réparation de ces structures consiste à les renforcer préventivement, avant que la fissure ne soit apparue. Le contexte de ce travail s'inscrit donc dans le cadre du renforcement préventif de structures par patchs composites afin de retarder l'apparition de fissures. Des essais de fatigue sur éprouvettes en aluminium 2024-T3 renforcées sont menés pour observer et quantifier l'aspect bénéfique du renforcement en termes de durée de vie. Une méthodologie de dimensionnement en fatigue sous sollicitations de service est également proposée. Parallèlement, la mesure d'échauffement par caméra infrarouge est utilisée pour aider à comprendre le processus d'endommagement et de cumul de dommage propres à cet alliage.
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Meyruey, Gwenaëlle. "Caractérisation et modélisation du vieillissement thermique d’un composite à base d’alliage d’Aluminium." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI092.
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Les composites à matrice métallique ont été développés dans les années 60 initialement pour les besoins de l’industrie aérospatiale. De nos jours, les alliages d’Aluminium à durcissement structural sont souvent combinés à des particules céramiques afin d’atteindre des propriétés de résistance élevées, maintenues à haute température, tout en conservant la légèreté de l’alliage, pour un coût faible. Cependant, l’utilisation de ces alliages nécessite une bonne connaissance des transformations microstructurales ayant lieu lorsqu’ils sont soumis à certaines conditions de température puisque des phénomènes de précipitation ont lieu et impactent les propriétés de résistance mécanique du matériau. De plus, la présence du renfort, induit des modifications microstructurales majeures et notamment lors des phénomènes de précipitation de la matrice. Ainsi, ces travaux de thèse portent sur un alliage d’Aluminium à durcissement structural de la série 6xxx qui, durant son utilisation, peut être confronté à des températures comprises entre 100°C et 350°C, et ayant une séquence de précipitation complexifiée par la présence de Silicium en excès et de particules de renfort céramiques. Les objectifs visés par ces travaux sont alors : 1) De décrire l’évolution microstructurale de l’alliage d’AlMgSi à excès de Silicium étudié, avec et sans particules céramiques. Ensuite, l’évolution de la résistance mécanique a été caractérisée à partir d’un état T6 lors de traitements isothermes, 2) De prédire ces évolutions microstructurales et les propriétés mécaniques qui en découlent par des modèles à base physique. La précipitation des principales phases de l'alliage étudié a pu être prédite grâce un modèle à champ moyen basé sur des lois classiques de germination-croissance et par une approche par classes de type KWN, en tenant compte : 1) de la compétition entre la phase cohérente et semi-cohérente, 2) d'une morphologie en bâtonnet avec un rapport de forme variable et propre à la phase modélisée. Ce modèle a permis, de tracer le diagramme Temps-Température-Transformation de l’alliage et du composite tout en tenant compte de l'accélération des cinétiques de précipitation en présence de renfort et attribuée à la forte densité de dislocations. Pour finir, 2 méthodes de prédiction des propriétés mécaniques ont été confrontées : 1) Une approche empirique de type JMAK (Johnson-Mehl-Avrami-Kolmogorov), 2) une approche à base physique. Malgré une prédiction proche des résultats expérimentaux par l'approche JMAK, cette méthode ne permet pas de remonter aux mécanismes physiques à l’origine des variations observées. Ainsi, l'approche à base physique basée sur le modèle de prédiction de la microstructure constitue une alternative prometteuse pour une prédiction plus précise des évolutions de propriétés de résistance mécaniques de ces matériaux même si de nombreuses adaptations restent à faire dans le cas du compositePrecipitation-strengthened alloys as Al-Mg-Si alloys reinforced with ceramic particles are an appropriate alternative for industrial applications. The precipitation sequence in Al-Mg-Si alloys is particularly complex when Silicon is in excess with respect to the Mg2Si composition and it is expected to be modified by the presence of the ceramic reinforcement. This is why, for industrial applications, under certain use conditions, it is fundamental to be able to predict the evolution of the microstructure in the alloy and the consequences on mechanical properties. The present work is devoted to the study of an age-hardenable Al-Mg-Si aluminium alloy which, can be facing temperatures between 100°C and 350°C in use conditions. This material is characterized by a complex precipitation sequence due to Silicon-excess and ceramic particles. The main objectives of the work are the following: 1) To describe how the microstructure evolves in the Al-Mg-Si alloy with silicon excess studied, with or without reinforcement, during a long storage period at a temperature between 100°C and 350°C. Then, it appeared necessary to describe the evolution of the mechanical properties in the same conditions but starting from a T6 state (corresponding to peak aged conditions). 2) To predict these evolutions (microstructure and strength) using an appropriate model. It was highlighted that the high silicon excess in the studied alloy leads to a simultaneous precipitation of several semi-coherent phases. Their precipitation has been predicted thanks to a KWN-type model based on classical nucleation-growth theories, validated by the experiments, and implemented considering: 1) the competitive precipitation between coherent et semi-coherent phases, 2) the rod-shape morphology of precipitates with a variable aspect ratio. This model has been used for the prediction of the Time-Temperature-Transformation diagram of the alloys and its composite considering the acceleration of the precipitation kinetics observed and attributed to the high dislocation density resulting from the presence of ceramic particles. Finally, 2 methods for the mechanical properties prediction have been compared: 1) a JMAK-type empirical approach 2) a physically based approach. The JMAK approach allowed us a quicker and easier prediction of the loss of hardness from the T6 state, for alloy and composite, during isothermal and non-isothermal treatment. Despite a prediction close to the experimental results, this approach cannot give us information about the physical mechanisms responsible for the observed mechanical variations. Then, a physically based approach taking into account the predictions of the precipitation model was used for the yield stress estimation during aging with a micromechanical model. This approach gave encouraging results and could be a powerful tool for the prediction of the strength during industrial use conditions
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Couch, P. D. "Fatigue and fracture of an aluminium-lithium based metal matrix composite at both ambient and elevated temperatures." Thesis, University of Birmingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499904.
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Kondapalli, Satyanarayana [Verfasser]. "Surface Modification of Aluminium Components by Developing Composite Coatings using Plasma Powder Arc Welding Process / Satyanarayana Kondapalli." Aachen : Shaker, 2007. http://d-nb.info/1166512908/34.
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JESUS, FILHO EDSON S. de. "Obtencao e avaliacao do comportamento a fadiga de compositos de matriz de aluminio submetidos a diferentes tratamentos superficiais mecanicos." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9273.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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TONELLO, KAROLINA P. dos S. "Compositos a base de Alsub(2)Osub(3) com adicoes de NbC e de MgO." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11780.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP