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1
Cooper, Daniel. "Reuse of steel and aluminium without melting". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245141.
Abstract (sommario):
Carbon dioxide emissions must be dramatically reduced to avoid the potentially dangerous effects of climate change. The steel and aluminium industries produce large amounts of carbon dioxide, accounting for 6% of anthropogenic emissions. Previous studies have shown that in these industries there is limited scope for further improvements in energy efficiency. Material efficiency strategies can, however, further reduce emissions. This thesis focuses on materially efficient reuse without melting. A scoping study of current reuse found three opportunities, an examination of which forms the basis of this thesis: reusing components at end of product life; extending the lifespan of products; and reusing manufacturing scrap. The opportunity to reuse components has received little attention to date and there is no clearly defined set of strategies or barriers to enable assessment of appropriate component reuse; neither is it possible to predict future levels of reuse. This thesis presents a global assessment of the potential for reusing steel and aluminium components. A combination of top-down and bottom-up analyses is used to allocate the final destinations of current global steel and aluminium production to final products. A substantial catalogue has been compiled for these products characterizing key features of steel and aluminium components including design specifications, requirements in use, and current reuse patterns. To estimate the fraction of end-of-life metal components that could be reused for each product, the catalogue formed the basis of a set of semi-structured interviews with industrial experts. The results suggest that approximately 30% of steel and aluminium used in current products could be reused. Barriers against reuse are examined, prompting recommendations for redesign that would facilitate future reuse. In order to understand how product lifespans can be extended it must first be understood why products are replaced. A simple framework with which to analyse failure is applied to the products that dominate steel use, finding that they are often replaced because a component/sub-assembly becomes degraded, inferior, unsuitable or worthless. In light of this, four products, which are representative of high steel content products in general, are analysed at the component level, determining profiles of cumulative steel mass over the lifespan of each product. The results show that the majority of the steel components are underexploited – still functioning when the product is discarded. In particular, the potential lifespan of the steel-rich structure is typically much greater than its actual lifespan. Evidence from twelve case studies, in which product or component life has been increased, is used to tailor life-extension strategies to each reason for product failure, providing practical guidelines for designers. There is currently no commercial method of reusing small manufacturing scrap; however, previous research has demonstrated that extruded profiles can be created from small clean aluminium scrap, the scrap fragments solid-state welding together when extruded. In order to evaluate potential applications for these profiles four case studies are conducted in collaboration with aluminium producers and product manufacturers. It was found that strong and formable profiles could be produced from scrap. However, contaminated scrap sources, unreliable bonding and poor surface quality limited their potential for commercial use. No model exists for solid-state weld strength that is applicable to scrap extrusion. This prevents optimisation of the existing extrusion process and the development of new, potentially better, processes. Subsequently, this thesis presents a new model of weld strength as a function of relevant deformation parameters. The model is evaluated using a new experiment in which the deformation conditions can be varied independently. The experiments establish the basic relationships between deformation parameters and weld strength. The model correctly predicts these trends with predicted weld strengths typically lying within the experimental error range. The technical assessment of reuse presented in this thesis demonstrates the scope of potential change. If implemented, the opportunities presented would greatly increase the reuse of steel and aluminium, reducing the emissions emitted from liquid metal production in conventional recycling.
2
Crane, Leonard W. "Melting and solidification of Zinc-Aluminium alloys". Thesis, Aston University, 1997. http://publications.aston.ac.uk/13278/.
Abstract (sommario):
Following a scene-setting introduction are detailed reviews of the relevant scientific principles, thermal analysis as a research tool and the development of the zinc-aluminium family of alloys. A recently introduced simultaneous thermal analyser, the STA 1500, its use for differential thermal analysis (DTA) being central to the investigation, is described, together with the sources of support information, chemical analysis, scanning electron microscopy, ingot cooling curves and fluidity spiral castings. The compositions of alloys tested were from the binary zinc-aluminium system, the ternary zinc-aluminium-silicon system at 30%, 50% and 70% aluminium levels, binary and ternary alloys with additions of copper and magnesium to simulate commercial alloys and five widely used commercial alloys. Each alloy was shotted to provide the smaller, 100mg, representative sample required for DTA. The STA 1500 was characterised and calibrated with commercially pure zinc, and an experimental procedure established for the determination of DTA heating curves at 10°C per minute and cooling curves at 2°C per minute. Phase change temperatures were taken from DTA traces, most importantly, liquidus from a cooling curve and solidus from both heating and cooling curves. The accepted zinc-aluminium binary phase diagram was endorsed with the added detail that the eutectic is at 5.2% aluminium rather than 5.0%. The ternary eutectic trough was found to run through the points, 70% Al, 7.1% Si, 545°C; 50% Al, 3.9% Si, 520°C; 30% Al, 1.4% Si, 482°C. The dendrite arm spacing in samples after DTA increased with increasing aluminium content from 130m at 30% to 220m at 70%. The smallest dendrite arm spacing of 60m was in the 30% aluminium 2% silicon alloy. A 1kg ingot of the 10% aluminium binary alloy, insulated with Kaowool, solidified at the same 2°C per minute rate as the DTA samples. A similar sized sand casting was solidified at 3°C per minute and a chill casting at 27°C per minute. During metallographic examination the following features were observed: heavily cored phase which decomposed into ' and '' on cooling; needles of the intermetallic phase FeAl4; copper containing ternary eutectic and copper rich T phase.
3
Hoult, A. P. "An experimental analysis of solid state pulsed laser melting of aluminium". Thesis, University of Warwick, 1999. http://wrap.warwick.ac.uk/36431/.
Abstract (sommario):
Novel aspects of solid state laser spot melting of aluminium using a pulsed solid state laser were investigated. After a thorough characterisation of the performance of the solid state laser, an initial series of ranging trials were performed to identify parameters which produced cosmetically satisfactory consistent melt spots on the surface of a commercially available aluminium alloy. These melt spots demonstrated a number of features of interest, including symmetrical concentric ring structures on the surface of the spots. A review of published literature on the use of laser beams as an intense radiation source for pulsed laser surface melting was carried out which confirmed that these phenomena have not been researched or reported in any depth. Experimental work identified the conditions under which they could be reliably reproduced, and these conditions are very close to laser parameters used commercially for pulsed laser welding. Further investigations to understand their origin involved using modified aluminium surfaces and temporally shaped laser pulses. Experimental details are included which will allow reliable reproduction of this effect in the future. Specific thresholds were identified for these phenomena and this has led to an improved understanding of solid state laser spot melting on aluminium. It appears that these rings are part of a continuum of irradiance which leads to melt expulsion due to reactive vapour pressure.
4
Louvis, Eleftherios. "Techniques for producing high relative density aluminium alloy components with selective laser melting". Thesis, University of Liverpool, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.632653.
Abstract (sommario):
Previous work has shown that the processing of aluminium alloys by Selective Laser Melting (SLM) is challenging, with fully dense components only being produced at high laser powers (minimum 330 W). The high laser power requirement for these parts is a problem as it is higher than that available in many SLM machines. Attempts to produce dense components by combining lower power and slow laser scanning speeds create a large melt pool that is difficult to control, leading to balling of the melted material and possible damage to the powder distribution system. Even when processing is carried out successfully, the laser scan speed, which has to be slower than 150 mm/s, increases build time and hence manufacturing costs. This thesis considers the changes that can be made to the SLM process to reduce the laser power required and to increase the laser scanning rates, while still producing components with a relative density approaching 100%. It also considers why aluminium and its alloys are much more difficult to process than stainless steels and commercially pure titanium. One reason for the difficulties in SLM of aluminium was the flowability of aluminium, which led to the redesign of the powder deposition mechanism of the SLM machines that were used. The major challenge for processing aluminium and its alloys was found to be oxidation due to the presence of oxygen within the build chamber. This formed thin oxide films on both the solid and molten materials. Examination of manufactured parts showed that when processing at laser power of 100 W the oxide films were broken between successive build layers due to Marangoni forces stirring the melt pool, but that walls of oxide were present between tracks within the same layer. As these films occurred in pairs one from each track, pores were formed in between creating open porosity.
5
Yoberd, Belmond. "An energy expert advisor and decision support system for aluminium melting and casting". Thesis, Kingston University, 1994. http://eprints.kingston.ac.uk/20580/.
Abstract (sommario):
The aim of this project was to develop and implement an expert advisor system to provide information for selecting and scheduling several items of small foundry plants using electric resistance bale-out furnaces, to optimise metal use and reduce energy costs. This involved study in formulating the procedures and developing a “foundry user friendly” expert system for giving advice to unskilled operatives in what was a complex multi- variable process. This system (FOES) included investigation and development of an advising system on the casting of a large numbers of different objects cast under different operating conditions and electricity tariffs. Knowledge elicitation techniques were developed and used during the complicated knowledge election process. Since this research programme intended to look at the complete process of melting, holding and pouring of the aluminium alloy, complex electricity tariffs were incorporated into the expert system in order to accurately calculate the energy cost of each process. A sub-section of the FOES system (DAD) could advise the unskilled foundry operative identify and eliminate the seven most common aluminium alloy casting defect by using a novel technique of incorporating actual defect photographs which were digitally scanned into the system.
6
Carroll, Lisa M. "Rapid steady state solidification of Al alloys". Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298796.
7
Jerrard, Peter George Eveleigh. "Selective laser melting of advanced metal alloys for aerospace applications". Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3576.
Abstract (sommario):
Research focused on the selective laser melting (SLM) of stainless steels and aluminium alloys. For steels, the possibility of creating a magnetically graded material was demonstrated as well as the ability to improve consolidation with austenitic and martensitic stainless steel powder mixtures. Stainless Steel/CoCr hybrid samples were also manufactured and tested to investigate the advantages of functionally graded materials (FGMs). Al alloy research began with examining the requirements for successful Al alloy consolidation in SLM and through experimentation it was found that Al alloys with good welding properties were the best choice: pure Al was found to be completely unsuitable. 6061 Al alloy was then used as a base material to manufacture Al-Cu alloy samples. Single layer SLM samples were produced first, which resulted in recognised Al-Cu microstructures forming. Multilayer Al alloy SLM research resulted in the discovery of the theorised ability to manufacture Al-Cu alloy parts with a nanocrystalline Al matrix with dispersed Al2Cu quasicrystals, resulting in a material comparable to a metal matrix composite that showed excellent corrosion resistance and compressive strength. Finally, a demonstration part was made to test the capability of the SLM process producing an aerospace type geometry using a customised Al alloy. Observations during manufacture and post process analysis showed that Al alloys were susceptible to changes in mechanical properties due to the geometry of the manufactured part.
8
ABREU, ALUISIO P. "Efeito de aditivos na resistência ao ataque em concreto refratário a base de sílica pela liga Al-5 (porcento)Mg". reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11342.
Abstract (sommario):
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
9
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.
Abstract (sommario):
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.
10
Furu, Jørgen. "An Experimental and Numerical Study of Heat Transfer in Aluminium Melting and Remelting Furnaces". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20249.
Abstract (sommario):
This work has been a combined experimental and numerical modeling effort aimed to help in the understanding of heat transfer processes when melting aluminium. In addition a newly developed type of oxy-fuel burner was investigated. Objectives set for this project include improving energy efficiency in a typical industry furnace used today and looking at possible new technology to realize higher efficiencies than normally obtained. As a starting point a literature review was done to get an overview of furnaces and technology used in aluminium remelting and recycling. The most commonly used furnace today for aluminium melting and remelting is the reverberatory furnace which was the focus of this work as well. Understanding the interaction of parameters influencing heat transfer and quantifying how heat is transferred in the furnace are key elements to be able to optimize energy efficiency. Reverberatory furnaces are usually heated by gas burners, more specifically with cold air as oxidizer. Recent developments in burner technology using pure oxygen as oxidizer has showed some promising results and was investigated in experiments and numerical models. Melting experiments were carried out in a controlled environment in a 500 kg laboratory scale furnace as a basis for understanding the heat transfer mechanisms and quantifying radiation and convection contributions when melting aluminium. The experiments also served as a reference for a numerical 1-dimensional heat transfer model along with more advanced 3-dimensional computational fluid dynamics (CFD) models using a commercial software package. Phenomena as turbulent flow, combustion, convection, conduction and radiation were included in the models along with latent heat release when melting metal. The influence and impact of physical parameters on the heat transfer could be determined in the numerical models and provided a more detailed analysis of the processes in the furnace. A newly developed Low Temperature Oxy-fuel (LTOF) burner was investigated and compared to a conventional cold air-fuel burner in a pilot scale furnace. Measurements of flame and furnace temperatures, gas composition and heat fluxes were done for both burners at two different input levels. Heating experiments of aluminium samples were performed to look at the difference between the burners for aluminium heating and melting applications. 3-dimensional CFD models were developed to determine unknown quantities such as metal emissivity and quantification of radiation and convection heat transfer. The experiments also confirmed the validity of the numerical models. Finally a full scale reverberatory industry furnace was modeled using a 3-dimensional CFD model. The air-fuel burners currently installed in the furnace was replaced by LTOF burners in the numerical model. The performance was compared to a previously published numerical model of the same furnace using air-fuel burners for two different metal configurations in the furnace. The influence of parameters such as burner input, metal emissivity, furnace wall emissivity and a dross layer was studied. The key factor when making improvements in furnaces is understanding the fundamental heat transfer processes in existing technology. The experimental and numerical modeling work presented in this thesis has studied these phenomena and created a basis from which further investigations into furnace efficiency in aluminium remelting and recycling can be done. The performance of a new type of burner was also analyzed and explained through experiments and modeling.
11
Dadbakhsh, Sasan. "Mechanical engineering : the selective laser melting of metals and in-situ aluminium matrix composites". Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3840.
Abstract (sommario):
Selective laser melting (SLM) is an additive manufacturing technique to produce complex three-dimensional parts through solidifying successive layers of powder materials on top of each other, from the bottom to top. The powder base nature allows the SLM to process a wide variety of materials and their mixtures and fabricate advanced and complicated composite parts. However, the SLM is a newly established process and seeks detailed scientific studies to develop new materials systems for the consumption of industry. These scientific studies are particularly important because of many issues associated with the SLM process, such as porosity, balling, delamination, thermal stress, etc, which can be varied from one material system to another. This PhD project aims to elucidate the fundamental mechanisms governing the microstructure and mechanical properties of the metallic and in-situ Al matrix composite parts made by SLM. The research starts with a preliminary study on SLM of stainless steel in order to explore the usage of SLM machine and related parameters. It illustrates the effect of part layout on the quality of products. The main research focuses on the in-situ formation of particulate reinforced Al matrix by using SLM of Al/Fe2O3 powder mixture. It is a pioneering research to integrate in-situ interaction with laser melting to produce advanced Al composites. It investigates the mechanisms governing SLM assisted in-situ reaction and also the effects of various parameters such as SLM layer thickness, laser power and scanning speed as well as the proportion of Fe2O3. It examines the influence of Al alloy powder and it describes the effect of hot isostatic pressing (HIP) post-treatment. The physical, mechanical, and metallurgical properties of the products are extensively assessed using various techniques. The processing windows of the process are sketched. The findings demonstrate unique microstructural features due to combined in-situ reaction and laser rapid consolidation, and contribute to provision of an in-depth scientific understanding of novel Al matrix composites by using SLM assisted in-situ processes. As part of this PhD project, industrial collaborative research has also been conducted to characterise the surface finish, metallurgical quality, process accuracy and mechanical properties of various SLM made metallic parts using Al, Ti, stainless steel, and super alloys. This part of research has generated scientific data and results for industrial applications of metallic fabrication using SLM.
12
Elkandari, Bader M. H. M. "Excimer laser surface melting treatment on 7075-T6 aluminium alloy for improved corrosion resistance". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/excimer-laser-surface-melting-treatment-on-7075t6-aluminium-alloy-for-improved-corrosion-resistance(c2da3b82-eeb5-4eae-a1dc-e4aefba18c62).html.
Abstract (sommario):
High strength 7xxx aluminium alloys are used extensively in the aerospace industry because the alloys offer excellent mechanical properties. Unfortunately, the alloys can suffer localised corrosion due to the presence of large intermetallic particles at the alloy surface that are aligned in the rolling direction. Laser surface melting (LSM) techniques offer the potential to reduce and/or to eliminate the intermetallic phases from the surface of the alloy without affecting the alloy matrix.The present study concerns the application of LSM using an excimer laser to enhance the corrosion resistance of AA 7075-T6 aluminium alloy. The initial stage of the project was aimed at optimising the laser conditions for production of a uniform microstructure, with the increase in the corrosion resistance of the alloy being determined by potentiodynamic polarization measurements in sodium chloride solution. Low and high laser energy densities were used with a different number of pulses per unit area to treat the alloy surface, which were achieved by changing both the laser fluence and the pulse repetition frequency. A laser fluence of 3.3 J/cm2 with 80 pulses was subsequently selected as the optimum condition to treat the surface of the alloy. The composition and microstructure of the alloy before and after LSM treatment, and following corrosion tests, were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD).After the laser treatment, the surface and the cross-sections of the alloy showed a significant reduction in the number of large intermetallic particles and a relatively homogenous melted layer was generated that provided significant improvement in the resistance of the alloy against corrosion, as assessed by several corrosion test methods, including exfoliation corrosion (EXCO) tests. However, delamination of the melted layer was observed after extended testing in the EXCO solution which is possibly related to the formation of bands of fine magnesium and zinc-rich precipitates within the melted layer. Therefore, anodising in sulphuric acid was applied to the LSM alloy, in order to further increase the corrosion resistance and to protect the laser treated layer from delamination by generating a thin oxide film over the LSM layer. The results revealed that the anodic treatment increased the resistance of the alloy to exfoliation attack.
13
Dokoupil, Filip. "Zpracování slitiny 2618 pomocí technologie selective laser melting". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231934.
Abstract (sommario):
This diploma thesis deals with finding and verification of appropriate technological parameters of SLM technology for the processing of aluminum alloy 2618. In the theoretical part, an introduction to additive manufacturing of aluminum alloys and general description of processes occurring during SLM production is given. Based on general knowledge were designed different types of testing samples produced by sintering the metallurgical powder using 400 W ytterbium fiber laser, which so far in the literature for aluminum alloy 2618 were not described. As the result, the technological parameters dependence on relative density and the detailed overview of the 2618 alloy processing by SLM technology is determined.
14
Yang, Deyu. "Rôle d'addition de magnésium sur l'occurence de la fonte naissante dans les alliages expérimentaux et commerciaux Al-Si-Cu et son influence sur la microstructure et les propriétés de traction de l'alliage = Role of magnesium addition on the occurence of incipient melting in experimental and commercial Al-Si-Cu alloys and its influence on the alloy microstructure and tensile properties /". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.
15
Ånmark, Niclas. "A calorimetric analysis and solid-solubility examination of aluminium alloys containing low-melting-point elements". Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103199.
Abstract (sommario):
The formation of liquid films is a widely known problem in aluminium heat exchanger materials. The phenomenon results in decreased brazeability along with severely deteriorated mechanical properties which might cause assembly collapse. In addition, low-melting-point elements like tin, bismuth and lead are thought to promote grain boundary sliding which is the main deformation mechanism during brazing. Their melting characteristics are not adequately reported in literature. It is therefore of great importance to examine the behaviour of these elements.The main objectives with this work is melting range determination of fin heat exchanger materials, melting detection of low-melting-point elements and calculation of tin, bismuth and lead solid-solubility in aluminium. This work does also involve distribution analysis of such elements in aluminium matrix after heat treatment.These investigations require development of a differential scanning calorimetry (DSC) technique that is applicable for analysis of aluminium fin heat exchanger material containing low-melting-point elements on ppm level. Optimization of the technique includes parameter control; like heating rate, sample mass, reproducibility and choice of crucible material. Laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) is additionally used in order to analyse solid solubility and distribution of low-melting-point elements in aluminium after heat treatment.The developed DSC technique shows a sensitivity limit in the range of 260-600 ppm. It means that it is not possible to detect melting of phases within and below that range. Solid solubility of tin was calculated for the three heat treatment temperatures, 400°C, 500°C and 625°C. Same procedure was applied on bismuth and lead. However, calculated values did not agree with Thermo-Calc. The distribution analysis indicate an exudation of trace elements i.e. diffusion toward surface during heat treatment.In conclusion, more knowledge regarding liquid films in aluminium fin heat exchanger material was obtained. Future work should be to further optimize the DSC technique for trace element analysis for concentrations below 100 ppm. The LA-ICP-MS technique is likely to improve experimentally unverified binary phase diagrams like Al-Bi, Al-Pb and Al-Sn phase diagrams. It can also be used to study exudation behaviour of liquid films.
16
Galy, Cassiopee. "Etude des interactions matériau/procédé en vue d'une optimisation des conditions opératoires du procédé de fabrication additive SLM sur des alliages d'aluminium pour des applications aéronautiques". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0106/document.
Abstract (sommario):
La fusion laser sélective d’un lit de poudres (Selective Laser Melting – SLM) connait un véritable essor depuis quelques années,notamment en ce qui concerne la production de pièces métalliques. La faible densité des alliages d’aluminium, conjuguée à l’optimisation de conception rendue possible grâce aux procédés de fabrication additive, assure un gain de masse des structures conséquent, ce qui intéresse fortement les industriels des domaines automobile et aéronautique. Cependant, les propriétés finales des pièces aluminium fabriquées par SLM dépendent des nombreux défauts sont générés lors de la fabrication (porosités, fissuration à chaud, état de surface, …). Cette thèse s’intéresse aux moyens de mieux maîtriser ces problèmes en explorant trois axes : Une identification et sélection des méthodes de caractérisations adaptées aux spécificités des matériaux métalliques élaborés par les procédés de fabrication additive « lit de poudre » a été mise en place. Par exemple, la comparaison de différentes méthodes de détermination de la densité relative de pièces nous a permis de montrer les avantages et inconvénients de chacune des techniques employées ; Une étude du moyen de fabrication SLM a mis en évidence l’influence de différents facteurs (flux de gaz, position des éprouvettes sur le plateau de construction, méthodes de dépôt de la poudre) sur les propriétés finales des pièces produites.Ces éléments ont un impact sur la densité des pièces, leurs propriétés de surface et leurs propriétés mécaniques. Nous avons ainsi constaté que la façon de positionner une pièce sur le plateau est une étape de la préparation d’une fabrication à ne pas négliger ; Les études paramétriques menées sur deux types d’alliages d’aluminium, AlSi7Mg0,6 et AM205, ont montré que la composition chimique de l’alliage d’aluminium employé influence de façon non négligeable le jeu de paramètres opératoires à appliquer pour fabriquer une pièce de manière optimale. La densité d’énergie volumique ψ, rapport de la puissance laser avec le produit de la vitesse de lasage, de la distance inter-cordons et de l’épaisseur de couche, est utilisée de façon classique pour l’optimisation des conditions opératoires en SLM. Nos études expérimentales à différentes échelles (1D et3D) ont permis de mettre en évidence les limites de ce critère. La combinaison de ces résultats à la simulation numérique du lasage d’un cordon de poudre a servi de base à la définition d’un premier modèle dont l’objectif sera à terme d’optimiser le choix des paramètres de fabricationInterest in selective laser melting (SLM) has been growing in recent years, particularly with regard to the production of metal parts.The low density of aluminum alloys, combined with the possible design optimization enabled by additive manufacturing processes,ensures a significant decrease in the mass of structures which is very interesting for manufacturers in the automotive and aerospaceindustries. However, it is difficult to control the final properties of aluminum parts manufactured by SLM because many defects, suchas porosity, hot cracking, and surface roughness, are generated during the process. To better understand how to optimize theperformance of SLM aluminium parts, several studies were conducted during this work: An identification and selection of characterization methods well-adapted to the specificities of metallic materials developedby powder bed additive manufacturing processes was established. For instance, the comparison of different methods ofdetermining the relative density of parts showed the advantages and disadvantages of each of the techniques; A study of the SLM machine highlighted the influence of various factors (gas flow, positions of specimens on the constructionplate, or methods of depositing the powder) on the final properties of the produced parts. These elements have an impacton the density of the parts, their surface properties, and their mechanical properties. We found that the positioning of a pieceon the tray is a critical step in the preparation of a build that is not to be neglected; Parametric studies carried out on two types of aluminum alloys—AlSi7Mg0,6 and AM205—have shown that the chemicalcomposition of the aluminum alloy used has a significant influence on the set of operating parameters required tomanufacture an acceptable aluminum alloy part. The energy density, ψ, which is the ratio of the laser power to the productof the lasing speed, the hatching distance, and the layer thickness, is conventionally used for the optimization of the operatingconditions in SLM. Our experimental studies performed at different scales (1D and 3D) have shown the limits of this criterion.The combination of these results with the numerical simulation of the lasing of a single powder bead served as a basis forthe definition of an initial model, the final objective of which will be to optimize the choice of manufacturing parameters
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Skulina, Daniel. "Zpracování Al-Sc hliníkové slitiny technologií SLM". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318760.
Abstract (sommario):
Master's thesis deals with the experimental determination of process parameters reaching densities >99 % for scandium modified aluminium alloy (Scalmalloy®) processed by SLM. The alloy achieves higher mechanical properties than the AlSi10Mg aluminum alloy commonly used. The theoretical part deals mainly with the results of Scalmalloy® alloys. Experimental bodies, testing methodology and evaluation method were designed on the basis of the theoretical parts,. The practical part is divided into four main stages: experimental determination of process parameters, a description of the effect of the parameters used on the relative density achieved, examination of the influence of process parameters on surface quality and mechanical testing. The mechanical properties were determined for the best parameters.
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VASCONCELOS, GETÚLIO de. "Estudo e desenvolvimento de suportes refratários para a fusão e a evaporação de urânio metálico". reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9290.
Abstract (sommario):
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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FERREIRA, MATHEUS C. "Obtenção de fritas vitroceramicas a partir de resíduos sólidos industriais". reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11469.
Abstract (sommario):
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Hradil, David. "Mechanicko strukturní charakteristiky materiálů vyrobených metodou SLM". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254320.
Abstract (sommario):
The master's diploma thesis deals with the mechanical and structural characteristics of aluminium-base alloy 2000 series, produced by selective laser melting (SLM). The experimental part of the thesis deal with selection of SLM processing parameters, influence of scanning strategy and evaluation of mechanical and structural characteristics of fabricated materials. Mechanical characteristics were evaluated based on results of tensile tests and microhardness measurement. Structural characteristics of materials produced by SLM were evaluated using metallographic analysis.
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Penmetsa, Sita rama raju S. "SCALE MODELING OF ALUMINUM MELTING FURNACE". UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_theses/331.
Abstract (sommario):
Secondary (recycled) aluminum constitutes around 48% of the total aluminum used in the United States. Secondary aluminum melting is accomplished in large reverberatory furnaces, and improving its energy efficiency has been one of the major interests to aluminum industries. To assist the industries in improving energy efficiency in aluminum melting, an experimental research furnace (ERF), with 907 kg (2000 lbs) capacity, has been built at the Albany Research Center of the U.S. Department of Energy as part of this multi-partner research program. To verify that the experimental results obtained in the ERF furnace are valid for the operation of industrial furnaces, we used scale modeling technology to assist the validation. In this thesis, scaling laws, which are applied to the thermal conduction loss through the model furnace, were developed and the partial modeling relaxation technique was applied to the development of modeling to derive achievable scaling laws. The model experiments were conducted in the model furnace, which was a one-fourth scaled-down version from the ERF furnace (as a prototype), and then compared to the tests in the ERF furnace. The temperature distributions across both the model and prototype were shown to be in good agreement. Confirmation of the scaling laws demonstrated the usefulness of the scale modeling concept and its applicability to analyze complex melting processes in aluminum melting.
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Ferreira, Matheus Chianca. "Obtenção de fritas vitrocerâmicas a partir de resíduos sólidos industriais". Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-14052012-111305/.
Abstract (sommario):
O resíduo estudado neste trabalho é originado do processo de obtenção de alumínio metálico, de grande interesse no Brasil pelo fato do país ser detentor de algumas das maiores reservas do mineral bauxita no mundo, utilizado como fonte de alumínio. Tendo como estratégia a geração de resíduo zero, colaborando para as tecnologias ambientalmente amigáveis, este trabalho estuda a incorporação de um resíduo resultante da recuperação de alumínio presente na escória gerada durante o processo de produção primária do alumínio metálico, por plasma térmico. Utilizando-se o diagrama de equilíbrio de fases do sistema Al2O3-CaO-SiO2, fez-se a adequação das composições visando a incorporação de resíduo no produto cerâmico sem alterar as características de processamento do material. A obtenção de vidros e de fritas vitrocerâmicas com o resíduo borra branca foi realizada fazendo-se a fusão das composições calculadas e, para os vitrocerâmicos, tratamento térmico posterior de devitrificação. Os produtos obtidos foram caracterizados utilizando-se técnicas de análise tais como difração de raios X (DRX), microscopia eletrônica de varredura (MEV) e espectroscopia do infravermelho (FTIR). Foi possível obter material vitrocerâmico com até 30% de resíduo de alumínio, após a fusão a 1300°C e devitrificação a 900°C. Em adição, o resíduo demonstrou ser um promissor material auxiliar na formação de fases cristalinas em baixos tempos de tratamento térmico.This work studies the residue obtained from the process of aluminum metal extraction activities, a great interest process, because of Brazil own some of the biggest bauxite mineral reserves in all the world. As a useful choice for no residue generation, and a support for environmentally friendly technologies, this work studies the white dross residue (WDR), from the process of aluminum metal reduction by thermal plasma. The phase equilibrium diagram of Al2O3-Ca O-SiO2 system was used to calculate the compositions. The WDR were incorporated in a ceramic product without modifying its principal characteristics. The fusion and devitrification treatments were studied. XRD (X-ray diffractometry), SEM (scanning electron microscopy) and FTIR (transformed Fourier infrared) were used to investigate the glass and glassceramic samples. These techniques showed that is possible to get glassceramic with up to 30 mass% of WDR after molten at 1300 deg C and annealed at 900 deg C. In addition, the WDR showed to be a promising material in attainment of crystalline phases in less times of heat treatment for annealing.
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Mohammadifard, Sara [Verfasser]. "Developing an innovative optical system for automatically monitoring the melting process in an aluminum melting furnace / Sara Mohammadifard". Garbsen : TEWISS - Technik und Wissen GmbH, 2019. http://d-nb.info/1204152098/34.
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Shafyei, Najafabadi Ali. "The kinetics of dissolution of high melting point alloying elements in molten aluminum". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40249.
Abstract (sommario):
Manganese and iron are two major alloying elements in various aluminum products. Since these elements have high melting points and low diffusivities in molten aluminum, their dissolution rates are very slow, when they are added to aluminum melts. In order to improve the kinetics of dissolution, several alloying methods have been introduced. All methods of alloying use mechanical stirring of some form or other to enhance dissolution rates by promoting forced convective mass transfer. In the present study, a comparison between the kinetics of dissolution of iron and manganese when added to the melt as discrete alloying particles or as compact briquettes (consisting of alloying elements and aluminum particles) was carried out. This study revealed that exothermic reactions and the local accumulation of heat within the briquettes can accelerate the kinetics of the alloy-making process.Using the results obtained, a model for the dissolution of briquettes in molten baths of aluminum is proposed. Following disintegration of the briquettes into the melt, fine particles disperse freely into the bath, while their dissolution being controlled by mass transfer. To predict the dissolution rates, the relative velocity between fine particles entrained in the turbulent field and the fluid must be known. However, such velocities are extremely difficult, if not impossible, to clarify, since the particles will be moving erratically with a turbulent liquid, in which, random velocity fluctuations will be superimposed on mean bulk flow velocities. As such, the hydrodynamic interactions which control particle-fluid mass transfer in an agitated vessel are highly stochastic and impossible to predict, ab initio. In order to quantify such phenomena two theoretical approaches have been introduced by aqueous model researchers. In this investigation, for the first time, these theories have been evaluated for a high temperature liquid metal system involving the dissolution of alloying particles.
In the evaluation of the terminal velocity theory in high temperature systems, water modelling experiments in conjunction with dimensional analysis between cold model and hot temperature system were carried out to study the entrainment behaviour of (heavy) alloying particles. Then, through continuous sampling of the melt, mass transfer coefficients and rates of dissolution of suspended particles in the melt were measured. A comparison between predicted values and measured results indicated that the terminal velocity theory, in conjunction with correlations proposed for aqueous systems, was not applicable to the high temperature alloying systems studied.
In Kolmogoroff's theory of local isotropy, mass transfer in a turbulent system can be treated by a single parameter, i.e. energy dissipation rate. High temperature experiments revealed that this approach could be applied to stirred alloying particles-molten aluminum systems. However, at higher rates of mixing, when a fully suspended condition is reached, further increases in input mixing energy have negligible effects on dissolution rates. Thus, as a practical measure, very high mixing rates are not recommended. In this regard, a correlation for mass transfer coefficient as a function of the rate of input energy was presented.
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Shuster, Riley Evan. "Modeling of aluminum evaporation during electron beam cold hearth melting of titanium alloy ingots". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44553.
Abstract (sommario):
Electron beam cold heart melting (EBCHM) is a consolidation and refining process capable of consolidating titanium scrap and sponge material into high quality titanium alloy ingots. Unlike other consolidation processes for titanium, EBCHM is efficient in removing both high and low density inclusions. During the final stage of casting in EBCHM, operators must balance the potential to form large shrinkage voids, caused by turning off the electron beam heating, against the tendency to evaporate alloying additions, which occurs if the top surface remains molten. To this end, a comprehensive understanding of the evaporation and fluid flow conditions occurring during the final stage of EBCHM is required in order to optimize ingot production. This research focused on developing a coupled thermal, fluid flow and composition model, capable of predicting the temperature, fluid flow and composition fields within an EBCHM cast, Ti-6Al-4V ingot. The physical phenomena of thermal and compositional buoyancy, mushy zone flow attenuation and aluminum evaporation were incorporated in the model formulation. Industrial scale experiments were carried out at the production facilities of a leading industrial producer of titanium to provide data and measurements used for model verification. The model has been used to study the effects of variation of electron beam power input and hot top time duration on the evaporative losses and position of solidification voids. Model predictions for liquid pool profile, last liquid to solidify and composition fields are in good agreement with the industrially measured results. Sensitivity analysis was performed by varying electron beam power and hot top duration independently and observing the effect on the composition fields and last liquid to solidify. For the cases examined, there was a strong correlation between electron beam power and alloying element losses, while hot top duration variation results indicated a stronger dependence on last liquid to solidify than on alloying element losses. Therefore a classic optimization problem arises between balancing hot top duration with alloying element losses.
26
Nounezi, Thomas. "Light Weight and High Strength Materials Made of Recycled Steel and Aluminum". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20523.
Abstract (sommario):
Recycling has proven not only to address today’s economical, environmental and social issues, but also to be imperative for the sustainability of human technology. The current thesis has investigated the feasibility of a new philosophy for Recycling (Alloying-Recycling) using steel 1020 and aluminum 6061T6. The study was limited to the metallurgical aspects only and has highlighted the potential of recycled alloys made of recycled aluminum and steel to exhibit substantially increased wear resistance and strength-to-weight ratio as compared to initial primary materials. Three alloy-mixtures are considered: TN3 (5wt% 1020 +95wt% 6061T6); TN5 (0.7wt% 1020 + 99.3wt% 6061T6); and TN4 (10wt% 6061T6 + 90wt% 1020). A Tucker induction power supply system (3kW; 135-400 kHz) is used to melt the alloy mixtures for casting in graphite crucibles. Heat treatment of the cast samples is done using a radiation box furnace. Microscopy, Vickers hardness and pin-on-disc abrasive wear tests are performed.
Casting destroyed the initial microstructures of the alloys leading to a hardness reduction in the as-cast and solution heat-treated aluminum rich samples to 60 Hv from 140 Hv. Ageing slightly increased the hardness of the cast samples and provided a wear resistance two times higher than that of the initial 6061T6 material. On the steel rich side, the hardness of the as-cast TN4 was 480 Hv, which is more than twice as high as the initial hardness of steel 1020 of 202 Hv; this hints to strong internal and residual stress, probably martensite formation during fast cooling following casting. Solution heat treatment lowered the hardness to the original value of steel 1020, but provided about ten (10) times higher wear resistance; this suggests higher ductility and toughness of normalised TN4 as compared to 1020. In addition, TN4 exhibits about 25% weight reduction as compared to 1020.
The actual recycling process and the effect of non-metallic impurities shall be investigated in future works. Also, the casting and heat treatment processes need to be improved.
27
Klein, Cândida Cristina. "A fusão zonal horizontal aplicada ao crescimento de policristais grosseiros de alumínio". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/18973.
Abstract (sommario):
A fusão zonal compreende uma família de métodos para controle e distribuição de impurezas na qual uma pequena zona fundida é deslocada lentamente ao longo de um material sólido, redistribuindo o soluto. Ela é utilizada na purificação de materiais, num processo denominado refino zonal, mas também pode ser usada na distribuição homogênea ou descontínua de impurezas e no crescimento de cristais. A fusão zonal aplicada ao crescimento de grãos, visando a obtenção de materiais mono ou policristalinos com grãos grosseiros é denominada recristalização por fusão zonal (ZMR) e seu uso principal é na preparação de materiais para fabricação de dispositivos eletrônicos e fotovoltaicos, especialmente em silício. Na última década, o progresso na tecnologia ZMR foi feito principalmente em três campos: desenvolvimento de equipamento, controle de processo e modelagem numérica, mas somente algumas pesquisas abordam a fusão zonal a baixas temperaturas e restringem a aplicação do método a outros materiais semicondutores como os elementos do grupo III, IV ou V. Deste modo, o presente trabalho tem como objetivo verificar a influência da velocidade de varredura, da largura da zona fundida e do número de passadas no processo de fusão zonal de materiais de baixo ponto de fusão, em relação à obtenção de materiais policristalinos com grãos grosseiros. Para tanto, construiu-se um equipamento de fusão zonal horizontal e barras de alumínio puro (P0610) foram submetidas ao processo, variando os parâmetros acima referidos. A macroestrutura das amostras foi analisada e os resultados obtidos do número de grãos/área foram interpretados, verificando a influência dos parâmetros físicos anteriormente citados, do gradiente térmico e do super-resfriamento constitucional. Verificou-se que a redução na velocidade de varredura e na largura da zona fundida, de modo geral, mostrou-se eficiente em relação à diminuição do número de grãos por área. Os resultados obtidos indicam que a fusão zonal foi efetiva na obtenção de alumínio policristalino com grãos grosseiros e colaboram para melhorar a compreensão do processo.The zone melting comprises a family of methods to control and to distribute impurities in which a small molten zone is moved slowly along a solid material, redistributing solute. It is used in materials purification, in a so-called zone refining process, but can also be used in homogeneous or discontinuous distribution of impurities and crystal growth. The zone melting applied to grain enlargement, leading to attain singlecrystalline or polycrystalline materials with coarse grains is so-called zone melting recrystallization (ZMR) and its major use is the preparation of materials for electronic and photovoltaic devices process especially silicon. In the last decade, progress in ZMR technology was done mainly in three areas: equipment development, process control, and numerical modeling, but only a few researches handle on zone melting at low temperatures and it limits the application of the method to other semiconductor materials such as III, IV or V group elements. Thus, this study aims to examine the influence of scan rate, zone width and the number of zone passes in the zone melting process of low melting point materials about getting polycrystalline materials with coarse grains. For this, horizontal zone melting equipment was built and pure aluminum bars (P0610) were zone melted, varying the parameters mentioned above. The macrostructure of the samples was analyzed and the results of the number of grains per area were assessed by checking the influence of physical parameters previously mentioned and the thermal gradient and the constitutional supercooling. It was found that scan rate and zone width reduction in general, proved to be efficient in reducing the number of grains per area. The results indicate that the zone melting was effective in obtaining aluminum polycrystalline coarse-grained and collaborate to improve the understanding of the process.
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Bradford-Vialva, Robyn L. "Development of a Metal-Metal Powder Formulations Approach for Direct Metal Laser Melting of High-Strength Aluminum Alloys". University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1620259752540201.
29
Rippe, Christian M. "Burnthrough Modeling of Marine Grade Aluminum Alloy Structural Plates Exposed to Fire". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/64154.
Abstract (sommario):
Current fire induced burnthrough models of aluminum typically rely solely on temperature thresholds and cannot accurately capture either the occurrence or the time to burnthrough. This research experimentally explores the fire induced burnthrough phenomenon of AA6061-T651 plates under multiple sized exposures and introduces a new burnthrough model based on the near melting creep rupture properties of the material.
Fire experiments to induce burnthrough on aluminum plates were conducted using localized exposure from a propane jet burner and broader exposure from a propane sand burner. A material melting mechanism was observed for all localized exposures while a material rupture mechanism was observed for horizontally oriented plates exposed to the broader heat flux. Numerical burnthrough models were developed for each of the observed burnthrough mechanisms. Material melting was captured using a temperature threshold model of 633 deg C. Material rupture was captured using a Larson-Miller based creep rupture model.
To implement the material rupture model, a characterization of the creep rupture properties was conducted at temperatures between 500 and 590 deg C. The Larson-Miller curve was subsequently developed to capture rupture behavior. Additionally, the secondary and tertiary creep behavior of the material was modeled using a modified Kachanov-Rabotnov creep model. Thermal finite element model accuracy was increased by adapting a methodology for using infrared thermography to measure spatially and temporally varying full-field heat flux maps. Once validated and implemented, thermal models of the aluminum burnthrough experiments were accurate to 20 deg C in the transient and 10 deg C in the steady state regions.
Using thermo-mechanical finite element analyses, the burnthrough models were benchmarked against experimental data. Utilizing the melting and rupture mechanism models, burnthrough occurrence was accurately modeled for over 90% of experiments and modeled burnthrough times were within 20% for the melting mechanism and 50% for the rupture mechanism. Simplified burnthrough equations were also developed to facilitate the use of the burnthrough models in a design setting. Equations were benchmarked against models of flat and stiffened plates and the burnthrough experiments. Melting mechanism burnthrough time results were within 25% of benchmark values suggesting accurate capture of the mechanism. Rupture mechanism burnthrough results were within 60% of benchmark values.Ph. D.
30
Kurian, Sachin. "Process-Structure-Property Relationship Study of Selective Laser Melting using Molecular Dynamics". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/104115.
Abstract (sommario):
Selective Laser Melting (SLM), a laser-based Additive Manufacturing technique has appealed to the bio-medical, automotive, and aerospace industries due to its ability to fabricate geometrically complex parts with tailored properties and high-precision end-use products. The SLM processing parameters highly influence the part quality, microstructure, and mechanical properties. The process-structure-property relationship of the SLM process is not well-understood. In the process-structure study, a quasi-2D model of Micro-Selective Laser Melting process using molecular dynamics is developed to investigate the localized melting and solidification of a randomly-distributed Aluminum nano-powder bed. The rapid solidification in the meltpool reveals the cooling rate dependent homogeneous nucleation of equiaxed grains at the center of the meltpool. Long columnar grains that spread across three layers, equiaxed grains, nano-pores, twin boundaries, and stacking faults are observed in the final solidified nanostructure obtained after ten passes of the laser beam on three layers of Aluminum nano-powder particles. In the structure-property study, the mechanical deformation behavior of the complex cellular structures observed in the SLM-fabricated 316L Stainless Steel is investigated by performing a series of molecular dynamics simulations of uniaxial tension tests. The effects of compositional segregation of alloying elements, distribution of austenite and ferrite phases in the microstructure, subgranular cell sizes, and pre-existing (grown in) nano-twins on the tensile characteristics of the cellular structures are investigated. The highest yield strength is observed when the Nickel concentration in the cell boundary drops very low to form a ferritic phase in the cell boundary. Additionally, the subgranular cell size has an inverse relationship with mechanical strength, and the nano-twinned cells exhibit higher strength in comparison with twin-free cells.Master of Science
Additive Manufacturing's (AM) rise as a modern manufacturing paradigm has led to the proliferation in the number of materials that can be processed, reduction in the cost and time of manufacturing, and realization of complicated part geometries that were beyond the capabilities of conventional manufacturing. Selective Laser Melting (SLM) is a laser-based AM technique which can produce metallic parts from the fusion of a powder-bed. The SLM processing parameters greatly influence the part's quality, microstructure, and properties. The process-structure-property relationship of the SLM process is not well-understood. In-situ experimental investigation of the physical phenomena taking place during the SLM process is limited because of the very small length and time scales. Computational methods are cost-effective alternatives to the challenging experimental techniques. But, the continuum-based computational models are ineffective in modeling some of the important physical processes such as melting, nucleation and growth of grains during solidification, and the deformation mechanisms at the atomistic scale. Atomistic simulation is a powerful method that can offset the limitations of the continuum models in elucidating the underlying physics of the SLM process. In this work, the influence of the SLM process parameters on the microstructure of the Aluminum nano-powder particles undergoing μ-SLM processing and the mechanical deformation characteristics of the unique cellular structures observed in the SLM-fabricated 316L stainless steel are studied using molecular dynamics simulations. Ten passes of the laser beam on three layers of Aluminum nano-powder particles have unfolded the formation mechanisms of a complex microstructure associated with the SLM process. The study on the deformation mechanisms of 316L stainless steel has revealed the contribution of the cellular structures to its superior mechanical properties.
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Loche-Moinet, Florent. "Modélisation électrothermique pour l’analyse et l’estimation de durée de vie de modules à semi-conducteurs en court-circuit". Electronic Thesis or Diss., Bordeaux, 2023. http://www.theses.fr/2023BORD0456.
Abstract (sommario):
L’électronique de puissance est en pleine croissance. De nombreuses questions de fiabilité sont apportées par le remplacement du silicium par du carbure de silicium, notamment concernant la tenue des composants aux courts-circuits. Aujourd’hui, il existe des modèles de prédiction de durée de vie restante dans le cadre d’une utilisation normale du composant, mais aucun modèle ne gère le cas d’un court-circuit. Or, avec des durées de vie aux alentours de la vingtaine d’années, la modification de la durée de vie restante suite à l’apparition d’un court-circuit est une problématique à intégrer pour optimiser les maintenances préventives ou correctives.La simulation numérique d’un court-circuit d’un module de puissance permettrait de déduire l’endommagement du module et la rectification à effectuer sur la prédiction de la durée de vie restante. Cette démarche étant innovante, de nombreux verrous technologiques et problématiques de modélisation ont dû être résolue. Tout d’abord, comme deux logiciels en éléments finis (ANSYS Mehanical et Sentaurus TCAD) sont utilisés qui ne communiquent pas naturellement entre eux, une passerelle pour permettre ce lien a dû être faite. Une modélisation électro-thermo-mécanique d’une cellule SiC MOSFET 1,2 kV 15 A est présentée dans cette thèse. Pour cette simulation numérique, un modèle de fusion de l’aluminium de surface est adapté et optimisé. Il a aussi été observé dans la littérature une localisation particulière des dégradations par court-circuit. Afin de considérer cette localisation, un modèle multi-échelle est réalisé avec une homogénéisation de la structure de grille de la cellule et une homogénéisation unidimensionnelle de la génération de chaleur de la cellule. Ce modèle est constitué d’une partie microscopique, la cellule, et d’une partie macroscopique, la puce. Ces travaux mettent en place de nouveaux outils pour la modélisation et la simulation de composants de puissance pendant un court-circuitPower electronics is experiencing significant growth. Many reliability issues arise from replacing silicon with silicon carbide, particularly concerning the component’s resistance to short circuits. Currently, there are models predicting the remaining lifespan under normal component usage, but none of them address the scenario of a short circuit. However, with lifespans typically around twenty years, the modification of remaining lifespan following a short circuit is a crucial consideration for optimizing preventive or corrective maintenance.The numerical simulation of a short circuit in a power module would allow deducing the damage to the module and the corrections needed for predicting the remaining lifespan. This innovative approach faced various technological challenges and modelling issues. Firstly, as two finite element software (ANSYS Mechanicaland Sentaurus TCAD) were used, which do not naturally communicate with each other, a gateway had to be established to facilitate this connection. An electro-thermo-mechanical modelling of a 1.2 kV 15 A SiC MOSFET cell is presented in this thesis. For this numerical simulation, a surface aluminium melting model is adapted and optimized. Literature has also indicated a specific localization of short-circuit-induced degradations. To consider this localization, a multi-scale model is created, involving homogenization of the cell’s gate structure and one dimensional homogenization of the cell’s heat generation. This model comprises a microscopic part, the cell, and a macroscopic part, the chip. These efforts establish new tools for the modelling and simulation of power components during a short circuit
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BAUDANA, GIORGIO. "γ-Titanium Aluminide Alloys for Aircraft and Automotive Engine Components Applications Processed by Electron Beam Melting". Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2699607.
Abstract (sommario):
γ-TiAl alloys are a family of intermetallic compounds which, thanks to their excellent physical and mechanical properties, are arousing big interest in the aerospace and automotive industries. In particular, they are considered an attractive alternative to nickel-based superalloys due to a lower density (about 4 g/cm3 for γ-TiAl alloys and 8 g/cm3 for Ni-based superalloys) that makes their specific mechanical properties comparable to those of nickel-based superalloys. The low weight of these materials allows to reduce the overall weight of the aircraft engine component or automotive engine component. As a result, it is possible to enhance the components performances and reduce fuel consumption and emissions. The low weight of γ-TiAl alloys, it will also contribute to achieve the targets for fuel-burn and emission reduction proposed by the European Commission and NASA.
The most applied conventional industrial scale processing routes for titanium aluminides include ingot casting, ingot forging, hot-rolling sheet production, investment and permanent mold casting and powder metallurgy processing. The processing of titanium aluminide via these conventional manufacturing methods can be complex due to the low ductility and fracture toughness of the material and casting process is an expensive solution and presents several problems such as the reactivity of the molten material with ceramics. The Electron Beam Melting (EBM) additive manufacturing technology is well known and considered for the processing of TiAl alloys, in particular for the aerospace application. This additive manufacturing technology uses an electron beam to generate parts by selectively melting the powder layer by layer according to CAD data. EBM technology allows to produce lighter and complex-shape components with a minimum material and energy waste.
The goal of this thesis was to investigate and characterize both γ-TiAl specimens and components produced by EBM and the heat treatments set-up in order to optimize the material properties. Since the starting material for the EBM process is the pre-alloyed powder, the characterization and the optimization of the powders was a fundamental preliminary step in order to guarantee a successful production of the final parts.
The experimental activities are related to four different TiAl alloys, three of which for aircraft engine application that are the 48-2-2 alloy (Ti-48Al-2Cr-2Nb (at.%)), the High-Niobium alloy (Ti-(45-47)Al-2Cr-8Nb (at.%)) and the TNM alloy (Ti-43.5Al-4Nb-1Mo-0.1B (at.%)) and one of automotive interest that is the so called RNT650 alloy (Ti-48Al-2Nb-0.7Cr-0.3Si (at.%)).
The TiAl 48-2-2 powder reuse investigation has demonstrated the possibility to reuse the powder up to six EBM cycles without a significant pick-up of contaminants, modification of particle size distribution, flowability and apparent density during the subsequent EBM jobs. This achievement means that, by reusing the powders for several cycles it is possible to obtain a considerable advantage in terms of cost and material saving. However, it is important to specify, that it is possible to mix the recycled powder with new powder between different cycles in order to maintain the proper powder characteristics.
The effect of the EBM processes parameters on the TiAl 48-2-2 material properties has been investigated by varying certain building parameters according to a Design Of Experiment (DOE) matrix. The study has shown that i) there is a parameters combination window in which the amount of process defects in the built material is very limited, ii) inside this window it is possible to perform a further fine parameters tuning in order to obtain an homogeneous microstructure and limit the evaporation of low-melting elements such as aluminum. In fact, this study has confirmed that the aluminum content and microstructure are very sensitive to the parameters variation.
Regarding the 3rd generation TNM alloy for aircraft engine application, it has been demonstrated the possibility to process it by EBM obtaining fully densified parts and, after a proper heat treatment, it has been possible to obtain the desired microstructures in order to improve the mechanical properties of the material according to the application.
The RNT650 alloy for the automotive application has been successfully processed by EBM and both massive specimens and lightweight hollow turbocharger wheels have been produced and characterized. Also in this case, a proper microstructure for the application has been obtained by means of a proper heat treatment. In addition, the characterization of a turbocharger wheel-shaft assembly prototype has been performed and it has shown a promising junction quality with a complete adhesion and without the presence of any defects at the interface.
Regarding the aircraft engine application of γ-TiAl, big part of the research activity was done in collaboration with AvioAero, within some European and Regional research projects. In particular, the 48-2-2 alloy as well as new generation alloys such as High Niobium alloy and TNM alloy produced by Electron Beam Melting were investigated in the frame of the European project E-BREAK.
Considering the automotive application, the part of the work on the RNT650 alloy was done within the European project TIALCHARGER.
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Wei, Wenjing. "Energy Consumption and Carbon Footprint of Secondary Aluminum Cast House". Thesis, KTH, Tillämpad processmetallurgi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122081.
Abstract (sommario):
Primary aluminum production brings about severe environmental burden due to its energy intensive process. Secondary aluminum production contributes to cutting off high energy demand around 90-95% and greenhouse gas emission by remelting scraps. However, previous research indicates melting furnace’s energy efficiency in secondary plant is still very low, which is around 26-29% and more than 70% heat is lost in different way. The objective of this project is to investigate energy consumption and greenhouse gas (GHG) emission in secondary aluminum cast house through process analysis. The result offers a comprehensive overview to aid decision-maker to compare energy consumption and environmental impacts caused by different product or process. This project has been done in collaboration with SAPA Heat Transfer. This project consists of two tasks. First task is aimed to give an overview of annual energy distribution and carbon footprint of per ton aluminum slab in SAPA cast house. In order to analyze energy distribution, mass and energy conservation has been applied for calculation. Meanwhile, International standard method, life cycle assessment, has been used to evaluate greenhouse gas contribution of the whole production process. The second task intends to investigate two effects (melting furnace type, raw material type) on products’ energy consumption and carbon footprint. Melting furnace’s effect is compared by selecting electric induction furnace and oxy-fuel furnace. On the other hand, raw material’s effect is studied by comparison of four different cast house products which have different raw material recipe. Calculation and analysis results indicates that per ton Sapa cast house aluminum slab consumes energy 3826MJ and contributes to 306kgCO2eq. green house gas. Meanwhile, comparison results show that oxy-fuel melting furnace has higher energy efficiency than electric induction furnace, however, it contributes much more GHG due to consumption of propane fuel. In addition, primary ingot has been concluded as distinct carbon footprint contribution than others contributors (i.e. fuel) for Sapa cast house’s slab.
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Gaytan, Guillen Sara Marisela. "Additive layer manufacturing of TI-6AL-4V by electron beam melting from powder particles solid, mesh and foam components study /". To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Ніколаєва, Н. В., e Т. В. Олевська. "Застосування стратегії більш чистого виробництва в процесі плавлення алюмінію". Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/11140.
Abstract (sommario):
У статті розглянуто спосіб впровадження стратегії більш чистого виробництва, який полягає у використанні шлаків від плавлення алюмінію в якості вторинної сировини. Цей процес розглянуто на прикладі заводу по виробництву алюмінієвих сплавів ТОВ «Альянс-Сервіс».
При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/11140
36
Bogen, Daniel J. "Effects of Manufacturing Defects on the Corrosion of Additively Manufactured AlSi10Mg". Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1596641889374996.
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TERNER, MATHIEU. "Innovative materials for high temperature structural applications: 3rd Generation γ-TiAl fabricated by Electron Beam Melting". Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2527509.
Abstract (sommario):
In the aeronautics industry, the propulsion systems stand among the most advanced and critical components. Over the last 50 years, gas turbine aeroengines were subjected to intensive research to increase efficiency and reduce weight, noise and harmful emissions. Together with design optimization, breakthrough in materials science for structural applications triggered the development of the most advanced gas turbine engines. For low temperatures, basically ahead of the combustion section, lightweight Ti alloys are preferred for their good mechanical properties. For high temperatures instead, Ni-based superalloys exhibit outstanding properties up to very high temperatures despite a rather high material’s density.
Research have focused on enhancing to the maximum the potential of materials in gas turbine engines. According to the application, the components experience various mechanical and environmental constraints. Special designs, manufacturing process, material compositions and protective coatings have been developed to push the limits of advanced materials. Nowadays, the attention is focused on innovative materials to replace the existing Ti and Ni based alloys leading to substantial benefits. Light weight composite materials in particular were found very attractive to replace some components’ Ti alloys. At higher temperatures, it is of great interest to replace Ni-based superalloys by materials with lower density and/or higher temperatures applications, which in turn would lead to substantial weight reduction and increase efficiency.
At the highest temperatures range, in particular in the combustion chamber and high pressure turbine sections, ceramic based materials offer promising balance of properties. Research are dedicated to overcome the drawbacks of ceramics for such structural applications, and in particular their brittle fracture behavior, by addition of reinforcing fibers. At lower temperatures range, TiAl based intermetallics emerged as very promising materials at half the density of Ni-based superalloys. Significant weight reduction could be achieved by the introduction of TiAl based alloys for rotating components of the compressor and low pressure turbine. 2nd generation γ-TiAl alloys were lately introduced in GE’s GEnx and CFM’s LEAP engines.
The present work concerns the fabrication by the additive manufacturing technique Electron Beam Melting of 3rd generation γ-TiAl alloys for high temperatures application in gas turbine aeroengines. EBM, building parts layer by layer according to CAD, offers many advantages compared to other manufacturing processes like casting and forging. Reported by Avio, 2nd generation γ-TiAl alloys have been successfully fabricated by EBM. To increase the material’s potential, the production of 3rd generation γ-TiAl alloys Ti-(45-46)Al-2Cr-8Nb was therefore studied. The optimization of the EBM parameters led to high homogeneity and very low post-processing residual porosity ≤ 1%. The fine equiaxed microstructure after EBM could be tailored towards the desired mechanical properties by simple heat treatment, from equiaxed to duplex to fully lamellar. In particular, a duplex microstructure composed by about 80 % lamellar grains pinned at grain boundaries by fine equiaxed grains was obtained after heat treatment slightly over the α transus temperature.
The study showed that addition of a higher amount of Nb significantly increased the oxidation resistance of the material, thus increasing the application temperature range of these γ-TiAl alloys.
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Kang, Nan. "Élaboration "in-situ" par mélanges de poudres de composites à matrice métallique au cours du processus de fabrication additive". Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0305/document.
Abstract (sommario):
La micro fusion laser d'un lit de poudre (SLM) permet la réalisation de pièces complexes avec des microstructuresfines. Cette technologie présente de nombreux avantages mais se heurte encore à une faible disponibilité des poudres d'alliages. En SLM, la pièce est d'abord conçue par CAO (conception assistée par ordinateur), puis construite couche par couche avec un faisceau laser commandé par un ordinateur. Dans ce cadre, le travail effectué dans cette thèse a consisté à étudier et à développer une nouvelle méthode pour réaliser des pièces en alliages et en composites à partir de mélanges de poudres élémentaires, ouvrant ainsi la voie à une grande variété de compositions.Au niveau expérimental le choix s'est porté sur le système aluminium-silicium avec différentes teneurs en silicium (12, 18 et 50% en poids). L'effet de l'ajout d'un champ magnétique statique a aussi été proposé comme un outil supplémentaire de contrôle de la microstructure.Dans le processus de fabrication de pièces par SLM la puissance du laser et la vitesse de balayage déterminent au premier chef la densité, la microstructure, la composition des phases et les propriétés mécaniques du produit. Une analyse systématique de l'effet de ces paramètres sur l'alliage Al - Si fabriqué par SLM à partir de mélanges de poudres est présentée. Des alliages ont été ainsi obtenus pour plusieurs domaines de composition visés correspondant à des applications pratiques (structures légères, système tribologique, emballage électronique, ...).Les microstructures fines obtenues grâce à la solidification rapide des matériaux fondus conduit à des propriétés quise comparent de façon favorable à celles obtenues avec les techniques classiques d'élaboration et de mise en oeuvreAs a new manufacturing technology, Selective laser melting (SLM) has a large potential in the manufacturing of complex parts with ultrafine microstructure.Selective laser melting has many significant advantages over traditional manufacturing methods but still faces a low availability of powder materials. With SLM, the part is firstly designed via 3D computer-aided design (CAD)), then built layer-by-layer with a high energy computer-controlled laser beam The work done in this study was therefore aiming at developing a new way to obtain alloys and composites directly from elemental powder mixtures with a large composition flexibility.Experimentally the choice was made of the aluminum-silicon system with several silicon contents (12, 18, 50 wt. %).Adding a static magnetic field was also considered as an additional way to control the microstructure. When parts are manufactured by SLM, laser power and scanning speed are the main parameters determining the density, microstructure, phase composition and mechanical properties. A systematic analysis of the role of these parameter on the manufacturing of Al - Si alloys by SLM from mixtures of powders was therefore conducted. Al - Si alloys with a very fine microstructure were thus obtained for several composition ranges corresponding to practical applications (lightweight structures, high wear resistance alloys, electronic packaging material, ...). The properties of the materials obtained in this way, according to the performed characterizations, compares favorably with those obtained via the conventional production technologies
39
Blanc, Olivier. "Elaboration sans conteneur sous atmosphères réactives de verres fluorés ZBLAN et optimisation des pertes par diffusion pour l'application aux fibres optiques de télécommunication". Grenoble INPG, 1995. http://www.theses.fr/1995INPG0004.
Abstract (sommario):
Cette etude a ete motivee par la necessite d'eliminer la dispersion observee sur les proprietes optiques de verres fluores zblan elabores par le procede de levitation sur film de gaz a partir de poudres dans des conditions identiques, et egalement de confirmer sur un plus large domaine de longueurs d'onde les excellents niveaux de performances obtenus pour certains de ces echantillons. A partir d'une revue preliminaire des differents facteurs influant typiquement sur la qualite optique des verres de fluorures, la recherche des causes de dispersion nous a conduits a analyser de maniere critique les differents stades de l'elaboration: du stockage des matieres premieres a l'affinage du bain fondu en levitation. Par ailleurs, compte tenu de l'importance de la maitrise de l'elaboration sans contact sur la reproductibilite, l'etude des transformations specifiques qui accompagnent notamment la fusion des poudres en levitation et la formation du bain fondu sous l'action de l'hexafluorure de soufre (sf#6), ainsi que l'exploration de voies nouvelles utilisant en particulier la fluoration in situ par le trifluorure d'azote (nf#3) ont permis l'amelioration et la simplification des procedures d'elaboration. Ainsi, une majorite de verres elabores au cours de cette etude et caracterises en diffusion optique a 90 et en tomographie a balayage laser, presente des performances optiques proches des meilleures valeurs rapportees dans la litterature. En particulier, les verres affines successivement sous sf#6 et nf#3 possedent des concentrations en defauts diffusants systematiquement inferieures a 500 par centimetre cube et des pertes par diffusion qui suivent la loi theorique de rayleigh sur le domaine de longueurs d'onde 488-1300 nm et qui, extrapolees a la longueur d'onde d'ultra-transparence de 2550 nm, sont proches des minima theoriques. Enfin, l'analyse des mesures optiques nous permet d'emettre une hypothese sur la nature et la taille des defauts diffusants generalement presents dans les verres elabores en levitation sous sf#6
40
Song, Bo. "Nouvelles voies de fabrication d'alliages métalliques à hautes performances à partir de poudres". Phd thesis, Université de Technologie de Belfort-Montbeliard, 2014. http://tel.archives-ouvertes.fr/tel-01004824.
Abstract (sommario):
La fusion sélective par laser (Selective Laser Melting, SLM), une des techniques de la fabrication additive (AM), permet la production de pièces en trois dimensions (3D) de formes complexes directement à partir de poudres métalliques. Elle présente de nombreux avantages significatifs par rapport aux méthodes traditionnelles de fabrication mais se heurte encore à une faible disponibilité des matériaux en poudre.Le travail effectué dans cette étude a donc consisté à étudier et à développer un nouveau moyen pour réaliser in situ des pièces en alliages et en composites à partir de mélanges de poudres.Au niveau expérimental le choix s'est porté sur le système Fer-Aluminium et sur un renforcement par des particules de SiC.Les essais ont permis de constater que dans le processus de fabrication de pièces par SLM la puissance du laser et la vitesse de balayage déterminent au premier chef la densité, la microstructure, la composition de phase et les propriétés mécaniques.À partir d'un mélange de poudres, des phases intermétalliques ont été obtenues en contrôlant les paramètres SLM. Un traitement thermique ultérieur influence les paramètres cristallins, le degré d'ordre et les propriétés mécaniques des pièces ainsi formées.Avec l'utilisation de poudres préalliées, un phénomène de texture a été observé prenant la forme de grains allongés/colonnaires orientés dans la direction de construction.Le renforcement de la matrice de fer par des particules de SiC de différentes tailles conduit à une modification structurale avec la formation de produits d'interaction, perlitie et martensite, conduisant à une amélioration de la résistance à la traction par rapport au Fe pur.
41
Clark, Jared A. "The Effects of Build Orientation on Residual Stresses in AlSi10Mg Laser Powder Bed Fusion Parts". Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1578819644598848.
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Боянівський, Владислав Петрович. "Підвищення ефективності печей для переплавки алюмінієвого брухту". Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/24376.
Abstract (sommario):
Магістерська дисертація на тему «Підвищення ефективності печей для переплавки алюмінієвого брухту»: 104 с., 35 рис., 12 табл., 4 додатки, 15 джерел.
Об’єкт дослідження – піч для переплавки алюмінієвого брухту.
Мета роботи – підвищення енергетичної ефективності та удосконалення конструкції печей для переплавки алюмінієвого брухту.
Проаналізовані основні способи підвищення енергетичної ефективності.
Наведені результати розрахунків енергетичної ефективності печі місткістю 6 т, потужністю 600 кВт, для переплвки алюмінієвого брухту.
Показано, що за рахунок зменшення терміну відкриття форкамер знизилися витрати підведеної теплоти в печі на 45 %, а за рахунок зміни теплоізоляційних шарів - на 21 %.
Підібрані газоспалюючі пристрої – пальники типу ГПП-5 та наведена схема їх розміщення в боковій передній стінці печі.
Виконані розрахунки енергетичної та економічної ефективності переводу печі з електричного нагріву на газовий, при цьому для газового нагріву витрати підведеної теплоти зменшуються на 9 – 10 % порівняно з електричним.
Розрахунками визначено, що використання газового нагріву порівняно з електричним економічно більш ефективно, оскільки витрати на природний газ в циклі плавки для модернізованої печі потужністю 600 кВт зменшуються приблизно на 10 %.
Розроблена конструкція печі з нахиленим склепінням, для якої порівняно з традиційним зменшується термін плавки у середньому на 11 %, а ККД підвищується на 7 %.
Для утилізації теплоти димових газів обрано односторонньо-голчастий металевий рекуператор для підігріву дуттьового повітря з площею поверхні нагріву 12 м2.
В результаті встановлення рекуператора температура димових газів знижується від 800 °С до 390 °С, при цьому температура дуттьового повітря підвищується від 20 °С до 350 °С. Величина економії палива складає 16,9 %.
На базі програмного забезпечення Solid Works побудовані геометричні моделі багатошарових стінок печі та отримані результати розподілу температурних полів по товщині огороджувальних конструкцій. Наведені результати співставні з експериментальними даними отриманими на реальних печах.
Передбачені заходи з безпечної і комфортної роботи в приміщенні науково-дослідної лабораторії та заходи з пожежної безпеки та безпеки в надзвичайних ситуаціях.
Розроблено стартап-проект за шаблоном Business Model Canvas.Master's dissertation on "Improving the efficiency of furnaces for aluminum scrap remelting": 104 p., 35 f., 12 tables, 4 applications, 15 sources. The object of the study is an oven for aluminum scrap remelting. The purpose of the work is to increase energy efficiency and improve the design of furnaces for aluminum scrap remelting. Analyzed the main ways of improving energy efficiency. Presented the results of calculations of the energy efficiency of a 6-ton capacity kiln with a capacity of 600 kW for the remelting of aluminum scrap. It is shown that due to reduction of the opening time of the firebox, the cost of the supplied heat in the furnace decreased by 45% and due to the change of the thermal insulation layers - by 21%. Selected gas-fired devices - burners type GPP-5 and the scheme of their placement in the side of the front wall of the furnace. The calculations of the energy and economic efficiency of the furnace conversion from the electric heating to the gas have been performed, while for the gas heating the costs of the supplied heat are reduced by 9 - 10% in comparison with the electric one. Calculations have shown that the use of gas heating compared to electric is economically more efficient, since the cost of natural gas in the melt cycle for a 600 kV upgraded furnace decreases by about 10%. Developed the furnace design with an inclined vault for which the average melting time decreases by 11% compared to the traditional one, and the efficiency increases by 7%. For utilization of flue gases heat was chosen one-sided-needle metal recuperator for heating of blown air with the area of the heating surface 12 m2. As a result of the installation of the recuperator, the temperature of the flue gases is reduced from 800 °C to 390 °C, while the ambient air temperature rises from 20 ° C to 350 C. The amount of fuel savings is 16.9 %. Based on the Solid Works software, constructed geometric models of the multilayer walls of the furnace and obtained the results of the distribution of temperature fields along the thickness of the enclosing structures. The presented results are comparable to the experimental data obtained on real furnaces. Made provision for safe and comfortable work in the premises of a research laboratory and fire and safety measures in emergencies. A startup project based on the Business Model Canvas template has been developed.
Магистерская диссертация на тему «Повышение эффективности печей для переплавки алюминиевого лома» 104 с., 35 рис., 12 табл., 4 приложения, 15 источников. Объект исследования - печь для переплавки алюминиевого лома. Цель работы - повышение энергетической эффективности и совершенствование конструкции печей для переплавки алюминиевого лома. Проанализированы основные способы повышения энергетической эффективности. Приведены результаты расчетов энергетической эффективности печи вместимостью 6 т, мощностью 600 кВт, для переплавки алюминиевого лома. Показано, что за счет уменьшения срока открытия форкамер снизились расходы подведенной теплоты в печи на 45%, а за счет изменения теплоизоляционных слоев - на 21%. Выбраны газосжигающие устройства - горелки типа ГПП-5 и приведена схема их размещения в боковой передней стенке печи. Выполнены расчеты энергетической и экономической эффективности перевода печи с электрического нагрева на газовый, при этом для газового нагрева расходы подведенной теплоты уменьшаются на 9 - 10% по сравнению с электрическим. Расчетами установлено, что использование газового нагрева по сравнению с электрическим экономически более эффективно, поскольку затраты на природный газ в цикле плавки для модернизированной печи мощностью 600 кВт уменьшаются примерно на 10%. Разработана конструкция печи с наклонным сводом, для которой по сравнению с традиционным уменьшается срок плавки в среднем на 11%, а КПД повышается на 7%. Для утилизации теплоты дымовых газов выбран односторонне-игольчатый металлический рекуператор для подогрева дутьевого воздуха с площадью поверхности нагрева 12 м2. В результате установки рекуператора температура дымовых газов снижается от 800 °С до 390 °С, при этом температура дутьевого воздуха повышается от 20 °С до 350 °С. Величина экономии топлива составляет 16,9%. На базе программного обеспечения Solid Works построены геометрические модели многослойных стенок печи и получены результаты распределения температурных полей по толщине ограждающих конструкций. Приведены результаты сопоставимы с экспериментальными данными полученными на реальных печах. Предусмотрены меры по безопасной и комфортной работе в помещении научно-исследовательской лаборатории. Разработан стартап-проект по шаблону Business Model Canvas.
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Huang, Chien-Chih, e 黃建志. "Optimization of Fuel Consumption in Aluminum Melting Furnace". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/34761819367145936114.
Abstract (sommario):
碩士國立高雄應用科技大學
機械與精密工程研究所
99
Due to the trend in the energy shortages, traditional metal smelting industry also hopes to increase the efficiency of energy use and improve the existing energy technologies to reduce energy consumption, so that the limited energy canbe used with greatest efficiency. When melting aluminum rods, the melting process will not only consume large amount of fuel, but also emit high-temperature exhaust gas. In order to reduce fuel consumption, heat recovery equipment and tool for evaluating effectiveness are needed. In this article, Visual C # programming language is used to design a simulation program for the aluminum melting furnace such thatthe errors and time-consuming by manual calculation are reduced and productivity is enhanced.Based on the results, various components of aluminum melting furnace and quantity of the material can be determined. The results of this study are as follows: (1) Heat-absorbing area is the most important control factor in this study. (2) The larger the ratio of Melting volume toendothermic area, the faster the melting rate is and the more fuel consumption is needed. (3) Engineering quality method of Taguchi parameter design can reduce the fuel consumption by 7.9% or so.
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Wei-LinSU e 蘇韋霖. "Parametric Research of Selective Laser Melting with Aluminum-Silicon Alloy Powders". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/h57jqg.
Abstract (sommario):
碩士國立成功大學
航空太空工程學系
105
In recent years, the development of metal additive manufacturing (MAM) has brought an innovative progress. Through the additive manufacturing process, the material will be stacked in layers, it will not be limited by the complexity of molding. Selective Laser Melting (SLM) technology is the key technology for the current metal manufacturing. It uses laser as the processing heat source, making the metal powder melt and rapidly cooling. SLM process presents great potential applications in the fabrication of complex parts with fine microstructure. In this study, AlSi10Mg alloy powder obtained by gas atomization process is used to study the parameters of SLM process. The effects of objective of this research is to investigate process parameters such as laser power, layer thickness, scanning speed and hatching distance on the relative density on the object. We then compare the microstructure through the SLM process and mechanical properties before and after heat treatment to determine the appropriate process parameters interval. Results show that the average relative density of the parameters is 96.03%, 99.58%, and 99.15%, with the energy density less than 40 J/mm^3, 40 to 75 J/mm^3, and more than 75 J/mm^3, respectively. Results also show that at the energy density value of 55 J/mm^3, the relative density values are greater than 99.8% and exhibit the optimal stability; therefore, defined as the optimum energy density values. The optimum mechanical properties were measured with this energy density parameter (P = 360 W, t = 0.05 mm, s = 550 mm/s, h = 0.24 mm). Compared with the traditional casting method, SLM helps increase tensile strength by 68%, yield strength by 45%; elongation by 13%, and hardness by 62%. The result demonstrates that the rapid cooling factor under the SLM process produces fine grain refinement to achieve excellent mechanical properties.
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Chen, Ming-Jyun, e 陳銘均. "Joining of Electromagnetic Steel Using Low Melting Point Aluminum Brazes and Active Solders". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/82482408309386367724.
Abstract (sommario):
碩士國立雲林科技大學
機械工程系
103
In order to raise motor effectiveness and heat emission efficiency, vacuum brazing and active soldering was used to join electromagnetic steel and high thermal conductivity metals. Four Al-Si-Cu based low-melting-point aluminum brazes and two active solders, Sn-Ag-Cu-Ti-Mm and Sn-Zn-Bi-Ti-Mm, were used in this study. For soldering, tradition soldering was compared with ultrasonic vibration soldering bonding. Experimental results showed that the rare earth element containing aluminum solders have high shear bonding strength. The ultrasonic vibration soldering shear strength was obviously higher than used traditional soldering. Tensile testing at elevated temperature showed that the bonding shear strength decreased.
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Gerlich, Adrian Piotr. "Local melting and tool slippage during friction stir spot welding of aluminum alloys". 2007. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=742311&T=F.
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Wei, Zong-Ying, e 魏宗潁. "Numerical Analysis of Stable Melting Pool Penetration for Aluminum Alloy wheel Frame TIG Welding Technique". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6tk3jp.
Abstract (sommario):
碩士國立屏東科技大學
車輛工程系所
106
This work used TIG (tungsten inert gas) welding technique to weld aluminum alloy wheel frame with the finite element analysis software ABAQUS .The process parameters were tried to change to achieve the goal of stable melting pool penetration. The process parameters of TIG welding consists rotating speed of rotary table, current of tungsten bar, initial temperature of work piece(aluminum alloy wheel frame)and current duration on initial position of welding. The simulation results showed that if this study used the initial process parameters to be set, the result could not achieve the wanted goal. The failure factor was found as follows: First of all, current duration on each position of welding was too long that led to overheat at end of welding path on work piece. Therefore, the goal could not be accomplished. But this question could be modified by building up the rotating speed of rotary table. Because when the rotating speed of rotary table increases that means the current duration on each position of welding will be decreased. It also means this method could not led to overheat on work piece. Next, melting pool penetration was not deep enough due to most of heat source energy (tungsten bar) will be absorbed by work piece. When TIG welding technique was used to weld workpiece(aluminum alloy wheel frame), the energy of heat source will be conducted and absorbed by it. Therefore, we could not accomplish the stable weld depth goal which we wanted. But we could increase current duration on initial position of welding to solve this question. It could be better that if the preheating was treated at initial position of welding on work piece. And then we could obtain the goal that a stable weld depth. This study got two optimization cases under rotating speed of rotary table at 2 rpm and 3 rpm by changing process parameters. It could increase current duration on initial position of welding or increase current value of tungsten bar to get enough welding depth. But we had to do preheating treatment for work piece before TIG welding under rotating speed of rotary table at higher speed (3 rpm). Hence, a stable welding depth could be obtained at high rotating speed utilizing the preheating treatment on workpiece.
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Tsai, Yii-Je, e 蔡易哲. "Brazing of 6061 Aluminum Alloy Using Low-Melting-Point Al-Si-Cu-X Filler Metals". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9by3bw.
Abstract (sommario):
碩士國立雲林科技大學
機械工程系
107
In the research,three low-melting-point aluminum brazing filler metals based on Al-Si-Cu were developed. The low melting point fillers with quaternary alloys by adding different proportions of Zn, Ge or Sn elements in Al-Si-Cu alloys were used to join 6061 aluminum alloy. In the first experimental procedure, the melting temperatures of the filler metals were determined by DSC. The microstructure and phase composition of filler metals before and after brazing were analyzed with OM, SEM and EDS. The optimal brazing parameters were confirmed. Finally, using the microhardness tester and the tensile tester to understand the changes of mechanical properties of the joints. The results of the metallographic analysis showed that the microstructures of the Al-9.6Si-10Cu-10Zn filler metal included Al2Cu phase, Si phase and Al-rich phase of solid solution of Al and Zn. The solidius temperature was 495℃ and liquidius temperature was 546℃. The metallographic structure of Al-10.2Si-10Cu-5Ge filler had Al2Cu phase, Si-Ge phase, Al-Si eutectic structure and Al phase substrate. The solidus temperature was 490℃ and the liquidus temperature was 550℃. The metallographic analysis showed that the microstructures of the Al-10.2Si-10Cu-5Sn filler metal included Al phase substrate and Al2Cu phase, Si phase, Sn phase and Al-Si eutectic. The solidus temperature was 503℃ and the liquidus temperature was 554℃. The three filler alloys were brazed under the optimal brazing parameters. The hardness of the joint interface was higher than the base metal. The highest shear strength was about 28~33MPa. The fracture of the shear test appeared in filler center. In addition, the 6061 aluminum alloy was precipitation hardened aluminum alloy. After brazing, strength and hardness of the base material decreased. The mechanical properties were recoverded by T6 heat treatment.
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Liu, Zheng-Bo, e 劉政伯. "Brazing of Stainless Steel with Copper Using Rare Earth Elements Containing Low Melting Point Aluminum Fillers". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/39984198692361285976.
Abstract (sommario):
碩士國立雲林科技大學
機械工程系碩士班
99
In this study, low-melting-point aluminum brazing filler metals based on Al-12Si were developed and used to join stainless steel with copper. The effects of the addition of copper, tin, germanium, and rare earth elements in Al-Si alloys upon the joining of stainless steel with copper were investigated. By way of differential scanning calorimeter(DSC), the melting points of Al-Si-Sn, Al-Si-Cu, Al-Si-Cu-Sn and Al-Si-Cu-Ge filler metals were determined. The results showed that the addition of 5 wt.% Cu into the Al-Si eutectic alloy caused of the liquidus decreased to 571℃；addition of 5 wt.% Sn into the Al-Si eutectic alloy caused of the liquidus decreased to 575℃；addition of 5 wt.% Sn and 5 wt.% Cu into the Al-Si-Cu filler metals caused of the liquidus decreased 563℃ and 567℃, respectively. Brazing with the low melting point aluminum fillers to join stainless steel and copper was carried out at 610℃ under high pure argon atmosphere for different holding time. After brazing, shear strength, fracture surface, interface microstructure and composition of the joints were analyzed. The results indicated that the FeSiAl5 intermetallic compound formed between filler metals and 304 stainless steel, AlCu and Al2Cu intermetallic compounds were found between filler metals and copper. The thickness of these intermetallic compounds on copper increased as brazing period increased.