Dissertations / Theses on the topic 'Aluminum castings'
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Ziolkowski, Joseph Edmund. "Modeling of an aerospace sand casting process." Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-1223102-102625.
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Chintalapati, Pavan. "Solidification under pressure of aluminum castings." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2010r/chintalapati.pdf.
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Thesis (Ph. D)--University of Alabama at Birmingham, 2009.Title from PDF t.p. (viewed June 30, 2010). Additional advisors: Viola L. Acoff, Krishan K. Chawla, Raymond J. Donahue, Gregg M. Janowski, Harry E. Littleton (ad hoc). Includes bibliographical references (p. 143-138).
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Escobar, de Obaldia Enrique R. "SIMULATION OF MICROPOROSITY IN ALUMINUM PLATE CASTINGS." MSSTATE, 2007. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04082007-152803/.
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Porosity is known to be one of the primary factors controlling fatigue life and total elongation in cast aluminum components. The thrust of this study is to examine pore nucleation and growth effects for predicting gas microporosity in A356 plates. In this work, a solidification model is used to quantify and evaluate the discrepancy between experimental data and porosity calculated with different approaches. The first approach considers hydrogen supersaturation based on the transport of dissolved hydrogen and Sievert?s law. The second approach uses the hydrogen supersaturation calculated in the first approach combined with a local solidification time. The third approach considers a new hydrogen technique based on the transport of inclusions through the liquid metal and mushy zone. Computer simulations were performed modeling aluminum plate castings.
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Raffaelli, Giovanni. "ADVANCED ALUMINUM ALLOYS FOR HIGH PERFORMANCE CASTINGS." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423780.
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In order to produce aluminum high performance castings, two main factors are essential: alloy and process. High performance castings are the result of the ideal equation of combination of these two factors. For this reason this PhD research project consisted in two main parts:
1. the first part has been developed together with Rheinfelden Alloys GmbH & Co. KG and consisted in an in deep analysis of aluminum alloys and their reinforcements mechanisms.
2. the second part has been developed in collaboration with TMB SpA and focused on the process and on process-related aspects affecting the quality of castings.
A new way to introduce nanoparticles to reinforce aluminum-silicon alloys was found and an in deep analysis of the very high mechanical properties obtained has been carried out. This way, in comparison to the processes to produce Al-alloy based nanocomposites already present in literature, is very cheap and could be scaled-up to industrial scale.
Nevertheless there are still some critical aspects in the use in industrial scale of these highly innovative nanocomposites and for this reason in the second part of the project has been studied how to produce high performance castings with already available alloys by optimizing the other factor of the equation: the process.
Based on the defect classification made by Gariboldi, Bonollo and Parona in the “Handbook of defects in high pressure die castings” (2010) [1], several aspects regarding the process were taken in account and relevant results were obtained in order to get always high performance castings.Al fine di produrre getti altoprestazionali in alluminio sono essenziali due fattori: la lega e il processo. Fusioni altoprestazionali sono il risultato dell’ideale equazione di combinazione di questi due fattori. Per questo motivo questo progetto di ricerca di dottorato consiste in due parti principali: 1. la prima parte è stata sviluppata in collaborazione con Rheinfelden Alloys GmbH & Co. KG e consiste in un’analisi approfondita delle leghe di alluminio e dei meccanismi del loro rafforzamento. 2. la seconda paste è stata sviluppata in collaborazione con TMB SpA ed è stata focalizzata sul processo e sugli aspetti del processo che possono influenzare la qualità dei getti. E’ stato sviluppato un nuovo metodo per l’introduzione di nanoparticelle al fine di rafforzare le leghe Alluminio-Silicio ed è stata svolta un’analisi approfondita delle notevoli proprietà meccaniche ottenute. Questo metodo, in confronto con gli altri processi per produrre nanocompositi a matrice lega di Alluminio presenti in letteratura, è molto economico e potrebbe essere sviluppato su scala industriale. Persistono tuttavia alcuni aspetti critici nell’utilizzo industriale di questi nanocompositi altamente innovativi e per questo motivo nella seconda parte del progetto è stato studiato come produrre getti altoprestazionali con leghe già disponibili ottimizzando l’altro fattore dell’equazione: il processo. Basandosi sulla classificazione dei difetti sviluppata da Gariboldi, Bonollo e Parona nel “Manuale di difettologia dei getti pressocolati” (2010) [1], sono stati presi in considerazione numerosi aspetti riguardanti il processo e sono stati ottenuti risultati rilevanti al fine di ottenere sempre getti altoprestazionali.
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Diem, Matthew M. "Development of a combined hot isostatic pressing and solution heat-treat process for the cost effective densification of critical aluminum castings." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0107103-162146.
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Moosavi, Khoonsari Elmira. "Reinforced aluminum structure castings for powertrain automotive applications." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66990.
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The reinforcement of an Al casting with ferrous inserts (hybrid systems) through a joining technique to utilize both Al alloys (lightness) and Fe-based alloys (stiffness) is of interest, especially in the transportation sector. This work focuses on different technological aspects of cast joining of cast iron to an Al alloy using an intermediate material (or coating). The experimental set up consisted of preparing the insert surface followed by coating the insert, and then, immersing it into an Al melt, and allowing the system to cool down to room temperature. The effects of flux treatment, decarburization, and the coating application, as well as the immersion time in the Al melt on the Al-Fe joint quality were investigated. The microstructure evolution of the reaction layer forming at the insert-coating interface was determined as a function of the coating time and the coating composition, and their effects on the joint properties were evaluated. The relationship between the microstructure and microhardness of the joint zone was established. Decarburization, flux treatment, suitable coating, and optimizing the process parameters improved the joint properties. Combination of "McGill 2" coating alloy and 1 min immersion time (in the Al melt) resulted in the formation of an Al-Fe joint with optimized characteristics. The results showed that the cast joining could be used to strengthen the Al castings and improve their performance.Le renfort des pièces coulées en aluminium par l'assemblage d'insertions ferreuses (systèmes hybrides) permet de combiner la légèreté de l'aluminium avec la rigidité des alliages à base de fer. Cette technique présente donc un grand intérêt pour plusieurs applications, spécialement dans le secteur des transports. Ce projet porte sur les différents aspects technologiques de la coulée de pièces avec joint aluminium-fonte auquel est ajouté une couche intermédiaire (ou revêtement). La procédure expérimentale a consisté à préparer la surface des insertions, à appliquer le revêtement, puis immerger la pièce dans un bain d'aluminium liquide, pour finalement refroidir le système jusqu'à la température de la pièce. Les effets du traitement par flux, de la décarburisation, et des paramètres de revêtement ainsi que la durée d'immersion dans l'aluminium liquide sur la qualité du joint aluminium-fonte ont été étudiés. L'évolution de la microstructure par la formation d'une zone de réaction à l'interface de l'insertion de réaction et zone du revêtement a été déterminée en fonction de la composition du revêtement er du temps d'immersion dans le revêtement liquide, et leurs effets sur les propriétés du joint été évalués. La corrélation entre la microstructure et la microdureté du joint ont a été établie. La décarburisation, le traitement par flux, l'utilisation d'un revêtement approprié et l'optimisation des paramètres du procédé améliorent significativement les propriétés du joint. L'utilisation du revêtement "McGill 2" avec un temps d'immersion dans le bain d'aluminium d'une minute permet la formation d'un joint Al-Fe avec des caractéristiques morphologiques, d'épaisseur, de microdureté et de composition optimisées. Les résultats montrent que l'insertion de pièces formant un joint peut être utilisée pour renforcer les pièces d'aluminium et
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Wu, Yaping. "Numerical analysis of direct-chill casting of aluminum ingot." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=672.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xi, 150 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references (p. 86-89).
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Palanisamy, Suresh. "Ultrasonic inspection of gas porosity defects in aluminium die castings." Australasian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20060828.103450.
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Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006.A thesis submitted to the Industrial Research Institute Swinburne, Swinburne University of Technology in fulfilment of the requirements to the degree of Doctor of Philosophy, 2006. Typescript. Includes bibliographical references (p. 199-211).
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Zhang, Chunhui. "Controlled cooling of permanent mold castings of aluminum alloys." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19619.
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The permanent mold casting process is a relatively popular and effective casting technology that can produce near-net-shape aluminum components with integrity, particularly for the automotive and aerospace industries. It is well recognized by the casting industry that it is essential to control the cooling of permanent mold castings in order to improve the quality of the castings, so there is a considerable incentive to develop a more effective method of mold cooling to control the temperature distribution of the mold and the casting. The current technologies for controlled cooling are air or water cooling passages and chill inserts. Each of these cooling methods presents certain disadvantages, and none offer optimum cooling control. Based on these considerations, a novel, effective and controllable water-based heat pipe has been successfully developed to be used as a new method of permanent mold cooling where high heat fluxes are normally encountered. Heat pipes featuring this design have been incorporated in an experimental permanent mold made of HI3 tool steel that contains three symmetric steps. Computer modeling for the permanent mold casting process has been accomplished to predict the effect and potential of heat pipe cooling for permanent mold casting. Castings of A3 56 alloy have been produced by this permanent mold. The effects of heat pipe cooling on permanent mold castings have been evaluated by analyzing the temperature distribution of the mold and the casting, as well as by measuring the dendrite arm spacing and shrinkage distribution of the castings. The effect of heat pipe cooling on the mold solidification time of castings of A356 alloy with different coating types was also studied. Industrial trials have been carried out to evaluate this new cooling technology on an industrial scale casting machine. Because the space around the mold installed on a low pressure die casting machine is very limited, it is often very difficult to install the heat pipe in the specific desired location in the mold. A new version flexible heat pipe cooling system has been developed for the industrial casting process. Preliminary and industrial tests of the heat pipe cooling system have been performed. The effects of heat pipe cooling, as well as the effects of using traditional water and air cooling on the low pressure die casting were studied. Data on the cooling rates obtained by heat pipes, as well as some microstructures and measurements of the dendrite arm spacing are presented in this thesis. Modeling and experimental results have shown that the water based heat pipe can provide high cooling rates in casting processes. The dendrite arm spacing (DAS) of A356 alloy is refined considerably by the heat pipes, and changes in the shrinkage pattern are provided by the dramatic changes in the heat flow patterns.
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Williams, Lyle. "Mechanisms of inclusion filtration and fluidity using prefil measurement on Al-7Si-0.4 Mg alloy melt report [thesis] submitted in partial fulfilment of the degree of Master of Engineering, Auckland University of Technology, April 2005." Full thesis. Abstract, 2005. http://puka2.aut.ac.nz/ait/theses/WilliamsL.pdf.
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Saha, Deepak. "Novel Processing Methods and Mechanisms to Control the Cast Microstructure in Al Based Alloys - 390 and Wrought Alloys." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-041405-150300/.
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Gales, ShaRolyn. "Effects of Pressurization on Aluminum 319 and A356.2 Alloy Castings." MSSTATE, 2001. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04062001-163331/.
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Castings made of aluminum 319 and A356.2 alloy were examined to determine the effectiveness of using pressure application during solidification to reduce porosity levels. Pyknometry was the method chosen to measure porosity. It was determined that the porosity of castings poured in both alloys was reduced in some instances. During the study, the surfaces of these castings were also examined and some were found to have defects present. After the porosity was evaluated, specimens of castings poured in both alloys were tested to determine whether or not the surface intrusions affected the castings. The defects were found to reduce the strength of the castings poured in aluminum 319. The castings poured in A356.2 did not have surface intrusions or any significant decreases in strength. Therefore it was concluded that of the two alloys tested, A356.2 alloy is most suited for using pressurization as a method of reducing porosity.
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Shang, Lihong. "Prediction of microporosity in aluminum silicon castings using criteria functions." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81564.
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Microporosity, a serious defect in Al-Si based castings, severely prevents their widespread applications in many critical conditions. The use of criteria functions to quantitatively predict microporosity level holds promise. To date, an ideal criteria function has yet to be obtained.In the present work, microporosity distribution in three prominently used hypoeutectic Al-Si alloys (319, 356, and 332) was investigated. The prediction effectiveness of single solidification parameter and existing criteria functions was evaluated by correlating thermal data from simulation studies to experimentally obtained microporosity values. Several new criteria functions are proposed based on experimental observation and multivariable regression analysis. The results indicate that the thermal parameters associated with the solidification process have a strong impact on the formation of the microporosity in Al-Si alloys. Thermal parameter-based criteria functions may be used to predict the microporosity in Al-Si castings but have their limitations. A general criteria function tf1.18 Vs1.13 (tf: local solidification time, Vs: solidification velocity) can be applied to predict microporosity for the family of hypoeutectic Al-Si casting alloys within 0.2 ~ 0.4 (%) error.
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Byczynski, Glenn Edwin. "The strength and fatigue performance of 319 aluminum alloy castings." Thesis, University of Birmingham, 2002. http://etheses.bham.ac.uk//id/eprint/7030/.
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Analysis of fatigue samples sectioned from commercial 319 (Al-Si-Cu-Mg) alloy cylinder block castings showed that shrinkage pore networks and oxide films played an important role in fatigue failure. A reduced pressure technique was employed to study the relationship between porosity and oxide films. Links between oxide films and porosity were made and mechanisms for the inflation of films into porosity networks were established. Tensile tests performed on samples cast with and without filters showed that the ultimate tensile strengths of the filtered group had a Weibull modulus 2.4 times that of the unfiltered. Samples with abnormally low strengths were found to contain oxide film defects. These films had an approximately 5 times greater damaging effect on strength than that predicted by reduction in cross sectional area. The fracture strengths of these flawed samples were found to obey a linear elastic fracture mechanics model (LEFM). A LEFM crack growth model was particularly successful in predicting the life of fatigue samples that initiated at oxide films. Having crack-like geometry, and a minute crack tip radius, oxide films effectively acted as preformed cracks. Consequently there was an absence of crack nucleation time, explaining the correlation of predicted propagation life to fatigue life.
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Schaffer, Paul. "Grain refiner fade in aluminium alloys /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18566.pdf.
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Dewhirst, Brian A. "Optimization of the heat treatment of semi solid processed A356 aluminum alloy." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-111705-111503/.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: microstructure; casting; Fluid Bed; Quality Index; Aluminum; A356; heat treatment; SSM; Semi Solid Metal Includes bibliographical references. (p.105-106)
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Te, Alino. "Improvement in Toughness of Castings through Chemical Surface Modification." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1271.
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Alloys with good toughness and elevated temperature properties like A201 are expensive and can be more difficult to process. This results in the use of heavier but less expensive alternatives in many applications where toughness is of concern, such as steels. Common alloys such as A356 and E357 are relatively cheap and easy to work with. However, these alloys have considerably lower toughness than premium alloys. This research aims to investigate surface modification treatments that could yield better toughness at a low cost in a common aluminum alloy. The process must show significant improvement in said properties, be cost effective, and easily adaptable in a common foundry. Diffusion of coating material into the substrate was investigated with a variety of coating metals. The diffusion process was facilitated in the solutionizing step for the given substrate aluminum in order to strengthen the sub-surface region of the parts. This research aims to provide a platform for further research into the practical effects of the coating and tempering on impact and toughness properties. These samples were characterized by optical and scanning electron microscopy, EDS, impact testing, and tensile testing.
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Warke, Virendra S. "Removal of Hydrogen and Solid Particles from Molten Aluminum Alloys in the Rotating Impeller Degasser: Mathematical Models and Computer Simulations." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0626103-111317.
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Barber, Lee P. "Characterization of the solidification behavior and resultant microstructures of magnesium-aluminum alloys." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-12234-112022/.
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Bainbridge, Ian Frank. "The influence of molten metal surface properties on the formation of surface defects on vertical direct chill cast aluminium alloy products /." [St. Lucia, Qld.], 2005. http://adt.library.uq.edu.au/public/adt-QU20060116.141809/index.html.
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Palanisamy, Suresh, and n/a. "Ultrasonic inspection of gas porosity defects in aluminium die castings." Swinburne University of Technology. Industrial Research Institute Swinburne, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20060828.103450.
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This thesis documents a PhD research program undertaken at Swinburne
University of Technology between the years 2000 and 2004. The research was
funded by the Cooperative Research Centre for Cast Metals Manufacturing and was
undertaken in collaboration with Nissan Casting Plant Australia Pty Ltd and the Ford
Motor Company Australia Limited. This thesis reports on the investigation of the
possibility of using an ultrasonic sensing-based, non-destructive testing system to
detect gas porosity defects in aluminium die casting parts with rough surfaces. The
initial intention was to develop a procedure to obtain ultrasonic signals with the
maximum possible amplitude from defects within the rough surface areas of the
castings. A further intention was to identify defects with the application of a suitable
signal processing technique to the raw ultrasonic signal. The literature review has
indicated that ultrasonic techniques have the potential to be used to detect subsurface
defects in castings. The possibility of classifying very weak ultrasonic signals
obtained from rough surface sections of castings through a neural network approach
was also mentioned in the literature. An extensive search of the literature has
indicated that ultrasonic sensing techniques have not been successfully used to detect
sub-surface defects in aluminium die castings with rough surfaces.
Ultrasonic inspection of castings is difficult due to the influence of
microstructural variations, surface roughness and the complex shape of castings. The
design of the experimental set-up used is also critical in developing a proper
inspection procedure. The experimental set-up of an A-scan ultrasonic inspection rig
used in the research is described in this thesis. Calibration of the apparatus used in
the inspection rig was carried out to ensure the reliability and repeatability of the
results. This thesis describes the procedure used to determine a suitable frequency
range for the inspection of CA313 aluminium alloy castings and detecting porosity
defects while accommodating material variations within the part. The results
obtained from ultrasonic immersion testing indicated that focused probes operating at
frequencies between 5 MHz and 10 MHz are best suited for the inspection of
castings with surface roughness Ra values varying between 50 [micro milli] and 100 [micro milli]. For
the purpose of validating the proposed inspection methodology, gas porosity defects
were simulated through side-drilled holes in the in-gate section of selected sample
castings. Castings with actual porosity defects were also used in this research.
One of the conclusions of this research was that it was extremely difficult to
detect defects in castings with surface roughness above 125 [micro milli]. Once the ultrasonic
signal data was obtained from the sample aluminium die castings with different
surface roughness values ranging from 5 [micro milli] to 150 [micro milli] signal analysis was carried
out. Signal feature extraction was achieved using Fast Fourier Transforms (FFT),
Principal Component Analysis (PCA) and Wavelet Transforms (WT) prior to passing
the ultrasonic signals into a neural network for defect classification. MATLAB tools
were used for neural network and signal pre-processing analysis. The results
indicated that poor classification (less than 75%) was achieved with the WT, PCA
and combination of FFT/PCA and WT/PCA pre-processing techniques for rough
surface signals. However, the classification of the signals pre-processed with the
combination of WT/FFT, FFT/WT and FFT/WT/PCA classifiers provided much
better classification of more than 90% for smooth surface signals and 78% to 84%
for rough surface signals. The results obtained from ultrasonic testing of castings
with both real and simulated defects were validated with X-ray analysis of the
sample castings. The results obtained from this research encourage deeper
investigation of the detection and characterisation of sub-surface defects in castings
at the as-cast stage. Implications for the industrial application of these findings are
discussed and directions for further research presented in this thesis.
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Pita, Claudio Marcos. "Modeling of oxide bifilms in aluminum castings using the Immersed Element-Free Galerkin method." Diss., Mississippi State : Mississippi State University, 2009. http://library.msstate.edu/etd/show.asp?etd=etd-03022009-105333.
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Mohanty, Pravansu Sekhar. "Studies on the mechanisms of heterogeneous nucleation of grains and pores in aluminum castings." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41722.
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In the present study, a fundamental theoretical and experimental investigation has been carried out on the mechanisms of heterogeneous nucleation of grains and pores in aluminum castings. A direct addition technique has been developed to introduce known types and quantities of inoculants into liquid aluminum alloys, irrespective of their wettability and chemical reactivity while preserving the surface characteristics and melt chemistry. Many different types of inoculants such as: $ rm Al sb2O sb3$, SiC, MgO, $ rm Mg sb2AlO sb4$, TiB$ sb2$, TiC, SrO and Sr(OH)$ sb2$ have been successfully added into liquid aluminum alloys, yielding single particulate distributions while avoiding incorporation of naturally occuring oxide films.The commercial grain refining practice of Al and its alloys has been experimentally simulated by introducing synthetic TiB$ sb2$ and TiC crystals into melts containing dissolved Ti. Experimental findings indicate that in the absence of dissolved Ti, TiB$ sb2$ crystallites alone do not nucleate $ alpha$-Al. TiC particles which are generally believed to be the nucleating substrate are unstable and form various complex carbides. In the presence of dissolved Ti even below the peritectic level, an interfacial layer of TiAl$ sb3$ is formed at the TiB$ sb2$/melt interface which subsequently nucleates the $ alpha$-Al. A 'duplex' nucleation mechanism is proposed based on the solute segregation phenomenon to the substrate/melt interface. In the case of hypoeutectic Al-Si alloy, this interfacial layer was found to be a ternary compound of Al-Si-Ti, however, a drastic drop in the peritectic solidification temperature presumably reduces its grain refining potency at higher Si content.
Particles which do not nucleate the solid phase and/or do not get engulfed by the growing solid, are continuously rejected by the solid/liquid (S/L) interface until the end of local solidification. These substrates act as a barrier to the fluid flow as well as to the diffusion field at the S/L interface, giving rise to enhanced gas segregation and viscous pressure drop. A novel theoretical mechanism for the heterogeneous nucleation of pores has been proposed, based on this behaviour of foreign particles at the advancing S/L interface. Mathematical analyses have been employed to predict the gas segregation and pressure drop in the gap between the particle and the S/L interface. An order of magnitude analysis is done, and it is shown that pressures in the range of the activation barrier can be obtained in normal castings. To substantiate the mechanism further, experimental studies were carried out by introducing various possible inclusions into liquid aluminum. The experimental findings are in line with the theoretical predictions.
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MERLIN, Mattia. "CORRELATION BETWEEN MICROSTRUCTURAL AND MECHANICAL PROPERTIES OF ALUMINUM ALLOY CASTINGS PRODUCED BY DIFFERENT FOUNDRY PROCESSES." Doctoral thesis, Università degli studi di Ferrara, 2009. http://hdl.handle.net/11392/2389203.
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Aluminum is quite a new material and the production of aluminumalloy
castings has greatly increased in the last recent years. Nowadays,
there is a continuous market requirement to produce lighter vehicles
and to increase fuel efficiency, therefore roughly two thirds of all
aluminum castings production is within the automotive field. Even
though the applications of aluminum in this scenario are considerable,
some aspects affecting the quality and the soundness of cast products
are still not fully understood. The aim of the research work presented
in this PhD thesis was to study the correlation between mechanical
and microstructural properties of Al-Si castings, in order to contribute
to fill this lack of knowledge. The majority of my research work is
included here as a collection of four papers submitted in the form they
were published or submitted for publication. Each paper is a standalone
work with separate abstract, introduction, experimental
procedure, results, conclusions and reference sections. Different kinds
of automotive and motorcycle structural components, realised by
means of low pressure die casting and permanent mould gravity
casting, and experimental components realised by sand mould casting
were produced and studied. Impact strength and tensile strength tests
were performed in order to understand the correlation between
microstructural and mechanical properties better. The effect of
different cooling rates, eutectic modification, defects, heat treatments
and type of cores was studied with the aim to improve the design of
aluminum alloy structural components. Moreover, the effect of the
eutectic microstructure on the anodizing surface treatment in
aluminum-silicon alloys was studied. The influence of silicon content,
morphology and distribution of the eutectic phase on the anodizing
process was investigated on both sand-cast and die-cast samples.
Different techniques for the microstructural examination were
employed in the research study; Optical Microscopes (OM) and
Scanning Electron Microscopes (SEM) with Energy Dispersive X-ray
(EDS) microprobe were used and also X-ray investigations were carried
out to verify the presence or the absence of porosities and defects in the
castings. In addition, numerical simulations were carried out and the
results were compared with those obtained by microscopy. In terms of
utility, the numerical simulations were able to predict the formation of
macro-defects and the final scale of microstructure within the castings,
confirming their potential as an engineering tool for predicting
microstructural and mechanical properties throughout the castings.
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Christensen, Adam Baxter. "The Feasibility of Augmenting a Fixed-Gap Bobbin Friction Stir Welding Tool with Cutters to Join Enclosed Castings." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6846.
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Bobbin Friction Stir Welding (BFSW) is a new application of Friction Stir Welding (FSW) that can be used to join materials together with little to no axial forces. This eliminates the need of a backplate or anvil needed to apply counter pressure against the tool. The applications of BFSW are growing every day. This new technology is helping the automotive industry and many other industries join materials more effectively and efficiently. This technology can be used to join materials with high strength to weight ratios to make cars lighter to increase fuel efficiency. This will also greatly reduce the cost of current joining technologies.The purpose of this research is to prove the feasibility of augmenting a BFSW tool with cutters to join enclosed castings while simultaneously removing ribs and variations in thickness by (1) penetrating a BFSW tool into the material away from an edge; (2) removing any inconsistencies in the material thickness while maintaining a weld; and (3) removing a BFSW tool from the casting away from an edge leaving a clean exit hole without destroying either the casting or the tool.
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Yousefian, Pedram. "Pore Formation in Aluminum Castings: Theoretical Calculations and the Extrinsic Effect of Entrained Surface Oxide Films." UNF Digital Commons, 2017. https://digitalcommons.unf.edu/etd/761.
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Aluminum alloy castings are being integrated increasingly into automotive and aerospace assemblies due to their extraordinary properties, especially high strength-to-density ratio. To produce high quality castings, it is necessary to understand the mechanisms of the formation of defects, specifically pores and inclusion, in aluminum. There have been numerous studies on pore formation during solidification which lead to hot tearing and/or reduction in mechanical properties. However, a comprehensive study that correlates pore formation theory with in situ observations and modeling assumptions from the literature as well as experimental observations in not available. The present study is motivated to fill this gap.
An in-depth discussion of pore formation is presented in this study by first reinterpreting in situ observations reported in the literature as well as assumptions commonly made to model pore formation in aluminum castings. The physics of pore formation is reviewed through theoretical fracture pressure calculations based on classical nucleation theory (i) for homogeneous and heterogeneous nucleation, and (ii) with and without dissolved gas, i.e., hydrogen. Based on the fracture pressure for aluminum, critical pore size and corresponding probability of vacancies clustering to form the critical-size pore have been calculated by using thermodynamic data reported in the literature. Calculations show that it is impossible for a pore to nucleate either homogeneously or heterogeneously in aluminum, even with dissolved hydrogen. The formation of pores in aluminum castings can only be explained by inflation of entrained surface oxide films entrained during prior damage to liquid aluminum (bifilms) under reduced pressure and/or with dissolved gas, which involves only growth, avoiding any nucleation problem. This mechanism is consistent with reinterpretations of in situ observations as well as assumptions made in the literature to model pore formation.
To determine whether damage to liquid aluminum by entrainment of surface oxides can be observed and measured, Reduced Pressure Tests (RPT) have been conducted by using high quality, continuously cast A356.0 aluminum alloys ingots. Analyses of RPT samples via micro-computer tomography (μ-CT) scanning have demonstrated that number of pores and volume fraction of pore in aluminum casting increased by raising the pouring height (i.e., velocity of the liquid). Moreover, pore size distributions were observed to be lognormal, consistent with the literature.
Cross-sections of RPT samples have been investigated via scanning electron microscopy. In all cases, the presence of oxygen was detected inside, around and between the pores. The existence of oxide films inside all pores indicates that oxide films act as initiation sites for pores and hydrogen only assist to growth of pores. For the first time, the pore formation is reconciled with physical metallurgy principles, supported by observations of oxide films in aluminum castings. Results clearly indicate that pores are extrinsic defects and can be eliminated by careful design of the entire melting and casting process.
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Tsumagari, Naoyuki. "Microstructural Features as a Measure of Process and Part Reproducibility in 390 Hypereutectic Aluminum-Silicon Alloy Die Castings /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487929230739219.
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Binney, Matthew N. "Porosity reduction in high pressure die casting through the use of squeeze pins /." [St. Lucia, Qld.], 2006. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19810.pdf.
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Ma, Shuhui. "A methodology to predict the effects of quench rates on mechanical properties of cast aluminum alloys." Link to electronic dissertation, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-050106-174639/.
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Dissertation (Ph.D.)--Worcester Polytechnic Institute.Keywords: Time-Temperature-Property curve, Jominy End Quench, ANOVA analysis. Quench Factor Analysis, Taguchi design, Polymer quench, Cast Al-Si-Mg alloys, Quenching, Heat treatment. Includes bibliographical references (p.115-117).
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Meduna, Radek. "Výroba rozlehlých tenkostěnných odlitků z hliníkových slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228297.
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The diploma thesis deals with the production of spacious thin-walled castings of aluminum alloys with a good surface quality. During the casting process, different types of molding sands and aluminum alloys are used. The target of the diploma thesis is to evaluate the casting surface quality, to analyse the defects and to evaluate the results.
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Whiting, Michael J. "An Investigation of Improving Wear of 390 Die-cast Aluminum Through Hardcoat Anodizing." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1006.pdf.
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Pereira, Manuel Filipe Viana Teotonio. "ADDITIVE MANUFACTURING OF COMPONENTS FOR IN-DIE CAVITY USE, SUITABLE TO WITHSTAND ALUMINIUM HIGH PRESSURE DIE CASTING (HPDC) PROCESS CONDITIONS." Thesis, Bloemfontein: Central University of Technology, Free State, 2013. http://hdl.handle.net/11462/243.
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Thesis (M. Tech. (Engineering: Mechanical)) -- Central University of Technology, Free State, 2013This research examines the suitability of Additive Manufacturing (AM) for manufacturing dies used in aluminium high pressure die casting. The study was guided by the following objectives: • The reviews of applicable literature sources that outline technical and application aspects of AM in plastic injection moulds and the possibilities of applying it to high pressure casting die. • To introduce AM grown die components in die manufacture. Further, to develop a methodology that will allow industry to apply AM technology to die manufacture. • Revolutionise the way die manufacture is done. The potential for AM technologies is to deliver faster die manufacture turnaround time by requiring a drastically reduced amount of high level machining accuracy. It also reduces the number of complex mechanical material removal operations. Fewer critical steps required by suitable AM technology platforms able to grow fully dense metal components on die casting tools able to produce production runs. • Furthermore, promising competitive advantages are anticipated on savings to be attained on the casting processing side. AM technology allows incorporation of features in a die cavity not possible to machine with current machining approaches and technology. One such example is conformal cooling or heating of die cavities. This approach was successfully used in plastic injection mould cavities resulting in savings on both the part quality as well as the reduction on cycle time required to produce it (LaserCUSING®, 2007). AM technology has evolved to a point where as a medium for fast creation of an object, it has surpassed traditional manufacturing processes allowing for rapidly bridging the gap between ideas to part in hand. The suitability of the AM approach in accelerating the die manufacturing process sometime in the near future cannot be dismissed or ignored. The research showed that there is promise for application of the technology in the not too distant future. In the South African context, the current number and affordability of suitable AM platforms is one of the main stumbling blocks in effecting more widespread applied research aimed at introduction of the technology to die manufacture.
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Lados, Diana Aida. "Fatigue crack growth mechanisms in Al-Si-Mg alloys." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0204104-125758.
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Thesis (Ph. D.)--Worcester Polytechnic Institute.Keywords: Microstructure; Elastic-Plastic Fracture Mechanics; Crack closure; A356; J-integral; Conventionally cast and SSM Al-Si-Mg alloys; Residual stress; Heat treatment; Fatigue crack growth mechanisms; Threshold stress intensity factor; Plastic zone; Paris law; Fracture toughness; Roughness. Includes bibliographical references.
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Ammar, Hany. "Effet des imperfections de la coulée sur les propriétés en fatigue des alliages de fonderie aluminium silicium = Effect of casting imperfections on the fatigue properties of aluminum-silicon casting alloys /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.
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Chen, Chien-Lung. "Evaluation of aluminum die casting defects causing casting rejection during machining." Connect to resource, 1997. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155309911.
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Schaub, Henning. "Comparison of different aluminium casting processes from an environmental perspective : Case study on plaster mould castings produced in Mid Sweden." Thesis, Mittuniversitetet, Avdelningen för ekoteknik och hållbart byggande, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-35659.
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While Aluminium has lots of unique properties and is seen as a material of the future, its production and manufacturing has significant environmental impacts. For complex and dimensional shapes casting remains the main manufacturing method and in this study the environmental pressure of different casting techniques is compared. A screening LCA is conducted to determine the environmental impacts of plaster mould castings in a case study at the Ventana Hackås AB foundry in Mid Sweden. The findings are compared to models of sand, pressure die and lost wax castings, based on literature datasets. The most relevant factors for the environmental performance are identified as the production of the aluminium alloy and the amount and source of energy. For plaster mould castings additionally the plaster consumption is significant, while lost wax castings are dominated by the mould production and general processes. Under similar circumstances a relatively similar performance was found for all casting techniques except the lost wax process, which is at least 3 times more emission intensive. Of the remaining techniques pressure die castings performed the best and plaster mould castings the worst, but different sources of uncertainties have been identified in this comparison. In addition a carbon footprint interface is created based on these findings, to enable specific comparisons of different casting method setups. Customizable variables allow the adaptation of three scenarios to real world conditions. As the main influencing factors the aluminium alloy, source of electricity and casting technique have been identified.2018-10-10
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Saleem, Muhammad Qaiser. "Helium Assisted Sand Casting of Aluminum Alloys." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/204.
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Sand casting is the most widely used casting process for both ferrous and non-ferrous alloys; however, the process is marred by large grain size structures and long solidification times. The coarser microstructure has a negative effect on the mechanical properties of the cast components and the long processing time affects the overall productivity of the process. The research reported herein addresses these problems for aluminum sand castings by enhancing the rate of heat extraction from the casting by replacing air, which is typically present in the pores of the sand mold and has a relatively low thermal conductivity by helium which has a thermal conductivity that is at least five times that of air in the temperature range of interest. The effect of (1) the flow rate of helium, (2) the way in which it is introduced into the mold, and (3) the mold design on (a) the average grain size, (b) the secondary dendrite arm spacing, and (c) the room temperature tensile properties of castings is investigated and compared to their counterparts produced in a typical sand casting process. In addition, a cost analysis of the helium-assisted sand casting process is performed and an optimum set of parameters are identified. It is found that when the helium-assisted sand casting process is performed with close to the optimum parameters it produces castings that exhibit a 22 percent increase in ultimate tensile strength and a 34 percent increase in yield strength with no significant loss of ductility, no degradation in the quality of the as-cast surfaces, and no significant increase in the overall cost.
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Hsu, Fu-Yuan. "Further developments of running system for aluminium castings." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289752.
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The purpose of this research is the development of guiding principles and rules for the design of running systems for aluminium castings, employing both the "virtual" experiment, a computational modelling package, and the "physical" experiment, the real-time X-ray radiography study. "Diverging-Bend" geometry has an essential feature in which the flow rate of the system could achieve the maximum and the velocity of advancing flow could reduce without developing surface turbulence. In liquid aluminium, the surface tension becomes more significant compared to water during the flow transformation from supercritical to subcritical velocities. To describe the phenomenon of hydraulic jump for liquid aluminium it is necessary to include the surface tension, giving the relation pV 2 = (pxgxH) + (4T/H) where p: density, V: average velocity, g: gravitational acceleration, H: the height of the hydraulic jump, and T: surface tension. Guidelines for the designing of L-junctions are developed. Five geometries of L-junctions can be applied and assembled in the design of runners and multiple-gate system. Progressive filling along the L-junction geometry can be achieved by reducing the area of the "dead zone". In a multiple-gate system uniform distribution of flow rate through each gate into the mould cavity is achieved. Quantification of a running system is established by the measurement of coefficient of discharge Cd. The loss coefficient K for individual component of runners is also estimated.
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Trejo, Eduardo. "Centrifugal casting of an aluminium alloy." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3041/.
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In centrifugal casting, molten metal is introduced into a mould which is rotated at high speed. The centrifugal force helps to fill thin sections but this benefit may be offset by the effect of the turbulent flow on the casting quality. In this research, the effect of direct and indirect gated mould designs on the quality and reliability of aluminium alloy investment castings made by centrifugal casting was investigated. The scatter in the ultimate bend strength and the modulus of elasticity was analyzed using the Weibull statistical technique, which showed that the Weibull modulus of both properties was significantly improved for the indirect gated cast test bars compared to the direct gated bars. A detailed microstructural characterization was carried out on the cast test bars, which included grain size, dendrite cell size and porosity. Scanning electron microscopy was used to examine and analyze the presence of defects on the fracture surfaces such as shrinkage pores, entrapped bubbles and oxide films resulting from surface turbulence during mould filling. The results indicated a clear correlation between the mechanical properties and the presence of casting defects. Water modelling experiments were carried out using purpose-built experimental centrifugal casting equipment and filling sequences recorded using a high speed video camera. The water modelling results showed that the general tendency for the direct and indirect gated mould designs was that the higher the rotational velocity, the lower the filling length and consequently the lower the filling rate. Subsequently, this information was used to validate the computer software ANSYS CFX. An excellent correlation was obtained between the experimental water modelling and simulation results for both direct and indirect gated moulds.
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Hogan, Patrick Alan. "Prediction and Reduction of Die Soldering." Digital WPI, 2008. https://digitalcommons.wpi.edu/etd-theses/523.
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Die Soldering occurs in aluminum permanent mold casting when the cast metal bonds with the die surface and remains stuck upon ejection of the part. Eventually, this layer builds up and production must be stopped for cleaning. It was estimated in a Contech squeeze casting plant in Pierceton, IN, that 1.5% of variable overhead can be directly attributed to die soldering. Previous work at WPI has focused on developing the mechanism of how soldering occurs. This work focuses on how that knowledge can be applied in an industrial setting. The work has focused on 4 major areas: (1) Using MAGMAsoft to predict die soldering, (2) Using surface metrology to measure die soldering, (3) Documenting the total process effects of using strontium modified casting alloys. The work has resulted in: (1) Guidelines for using MAGMAsoft to predict die soldering. The results can be incorporated into the existing MAGMA die soldering module, but provide more accurate time and temperature criteria. (2) The results of the study prove that measurement of the surface of the cast part itself can be used as a method for quantifying die soldering. (3) The total process effects of Sr-modification are reported, along with suggestions for immediate use of Sr-modification at the Pierceton, IN casting plant and guidelines for using Strontium in the future.
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Tenekedjiev, Nedeltcho. "Strontium treatment of aluminum : 17% silicon casting alloys." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61774.
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Joseph, Carolyn M. "Detection of Floating Grains in DC Aluminum Casting." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109015.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 42-44).
Free-moving "floating" grains have been linked to macrosegregation in direct-chill (DC) aluminum castings. The presence of these grains in the sump of a solidifying ingot has been acknowledged based on measurements of cast microstructures and by recent work using a turbulent jet to suspend solute-poor grains and minimize macrosegregation.1,2 Experiments in this study were designed to sample grains from the mushy region of two ingots, one cast by the standard method and another stirred with a turbulent jet. Measurements of floating grain size, concentration, morphology, and chemical composition are reported. The observations from the standard ingot offer a point of comparison for floating grain theories and casting models. The measurements from the stirred ingot show how the turbulent jet modifies the distribution, concentration and morphology of the floating grains.
by Carolyn M. Joseph.
S.M.
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Forté, Martin. "Modélisation de l'écoulement de l'aluminium semi-solide dans le moulage sous pression /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.
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Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2006.La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en génie. CaQCU Bibliogr.: f. [142-145]. Document électronique également accessible en format PDF. CaQCU
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Lee, Peter D. "The formation of hydrogen porosity during the solidification of aluminium alloys." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318700.
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Keles, Ozgur. "Production And Characterization Of Alumina Fiber Reinforced Squeeze Cast Aluminum Alloy Matrix Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609726/index.pdf.
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The aim of the present study was to investigate the effects of different levels of Saffil alumina fiber addition, magnesium content in aluminum alloy matrix and casting temperature on the mechanical behavior, microstructure and physical properties of short fiber reinforced aluminum matrix composites. The main alloying element silicon was kept constant at 10 wt%. Magnesium contents were selected as 0.3 wt% and 1 wt%. Saffil alumina fiber preforms varied from 10 to 30 vol%. The casting temperatures were fixed at 750 °C and 800 °
C. Micro porosity was present at the fiber-fiber interactions. Closed porosity of the composites increased when fiber vol% increased, however, variation in casting temperature and magnesium content in matrix did not have influence on porosity. Hardness of the composites was enhanced with increasing fiber vol%, magnesium content in matrix and decreasing casting temperature. Alignment of fibers within the composite had an influence on hardness
when fibers were aligned perpendicular to the surface, composites exhibited higher hardness. The highest hardness values obtained from surfaces parallel and vertical to fiber orientation were 155.6 Brinell hardness and 180.2 Brinell hardness for AlSi10Mg1 matrix 30 vol% alumina fiber reinforced composite cast at 800 °
C and at 750 °
C, respectively. 30 vol% Saffil alumina fiber reinforced AlSi10Mg0.3 matrix composite cast at 750 °
C showed the highest flexural strength which is 548 MPa. Critical fiber content was found as 20 vol% for all composites.
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Turkyilmaz, Gokhan. "Processing And Assessment Of Aluminum Ceramic Fiber Reinforced Aluminum Metal Matrix Composite Parts For Automotive And Defense Applications." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610751/index.pdf.
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The aim of this study was to produce partially reinforced aluminum metal matrix
composite components by insertion casting technique and to determine the effects
of silicon content, fiber vol% and infiltration temperature on the mechanical
properties of inserts, which were the local reinforcement parts of the components.
Silicon content of alloys was selected as 7 wt% and 10 wt%. The reinforcement
material, i.e. Saffil fiber preforms, had three different fiber vol% of 20, 25 and 30
vol% respectively. The infiltration temperatures of composite specimens were fixed
as 750 °C and 800 °
C. In the first part of the thesis, physical and mechanical properties of composite specimens were determined according to the parameters of silicon content of the matrix alloy, infiltration temperature and vol% of the reinforcement phase. X-ray diffraction examination of fibers resulted as the fibers mainly composed of deltaalumina fibers and scanning electron microscopy analyses showed that fibers had planar isotropic condition for infiltration. Microstructural examination of composite specimens showed that appropriate fiber/matrix interface was created together with small amount of micro-porosities. Bending tests of the composites showed that as fiber vol% increases flexural strength of the composite increases. The highest strength obtained was 880.52 MPa from AlSi10Mg0.8 matrix alloy reinforced with 30 vol% Saffil fibers and infiltrated at 750 °
C. Hardness values were also increased by addition of Saffil fibers and the highest value was obtained as 191 HB from vertical to the fiber orientation of AlSi10Mg0.8 matrix alloy reinforced with 30 vol% Saffil fibers. Density measurement revealed that microporosities existed in the microstructure and the highest difference between the theoretical values and experimental values were observed in the composites of 30 vol% Saffil fiber reinforced ones for both AlSi7Mg0.8 and AlSi10Mg0.8 matrix alloys. In the second part of the experiments, insertion casting operation was performed. At casting temperature of 750 °
C, a good interface/component interface was obtained. Image analyses were also showed that there had been no significant fiber damage between the insert and the component.
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Iversen, Fionn. "Meniscus Dynamics in Aluminium Extrusion Ingot Casting." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-527.
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In the modern process of continuous Direct Chill (DC) hot top casting of aluminium extrusion ingot with gas slip, poor surface quality of the cast ingot can still be a problem. In the worst cases pronounced surface wrinkling may occur coupled with periodic zones of reduced grain size, macrosegregation and exudation at the surface. The observed surface irregularities are believed to be linked to periodic oscillations or folding of the free molten aluminium surface in the mould, the meniscus, resulting in varying solidification conditions. The focus of this work is to gain a better understanding of the dynamics of the meniscus and the effect it has on ingot surface formation.
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Cockfield, Tracey J. "Twin-roll casting of aluminium eutectic alloys." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270607.
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Campo, Kaio Niitsu 1988. "Uso da extrusão em canal angular na produção da liga A356 para tixoconformação." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265929.
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Orientador: Eugênio José ZoquiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho investigou o uso da extrusão em canal angular (ECA) na produção de matéria-prima para tixoconformação visando à obtenção de uma rota simples e eficiente na formação de microestruturas globulares. Para tanto, uma liga de alumínio A356 foi submetida a um único passe ECA e, em seguida, reaquecida ao estado semissólido a 580°C. Dessa forma, pôde-se determinar a evolução morfológica e os mecanismos envolvidos na formação da pasta metálica, a influência do tratamento isotérmico na evolução microestrutural no estado semissólido, o comportamento de deformação durante a compressão a quente e o comportamento mecânico em tração do material tixoconformado. Os resultados indicaram que apenas um passe ECA foi suficiente para gerar uma pasta metálica refinada e globular apenas com o reaquecimento da matéria-prima. O engrossamento da microestrutura durante o tratamento isotérmico foi controlado principalmente pelo mecanismo de Ostwald ripening, fato comprovado pelo baixo valor da constante taxa de engrossamento K, o que mostrou a estabilidade dessa pasta no estado semissólido. As amostras exibiram comportamento tixotrópico típico com baixos valores de viscosidade aparente, na faixa de 10^2 a 10^3 Pa.s para as taxas de cisalhamento testadas. Por fim, as amostras tixoconformadas apresentaram valores de ductilidade e resistência à tração superiores aos das amostras fundidas e deformadas por um passe ECA
Abstract: This work investigated the use of equal channel angular pressing (ECAP) for the production of raw materials for thixoforming in order to obtain a simple and efficient processing route to generate globular microstructures. Therefore, an A356 aluminum alloy was processed by one ECAP pass, and then reheated to the semisolid state up to 580°C. Thus, it was possible to determine the morphological evolution and mechanisms involved in the formation of the semisolid slurry, the influence of isothermal treatment on microstructural evolution in the semisolid state, the deformation behavior during hot compression tests and the tensile properties of the thixoformed material. The results indicated that a single ECAP pass was sufficient to promote a refined and globular semisolid slurry. Microstructure coarsening during the isothermal treatment was mainly controlled by Ostwald ripening, which was verified by the low rate constant K, showing the stability of the reheated material in the semisolid state. The samples exhibited typical thixotropic behavior with low apparent viscosity ranging from 10^2 to 10^3 Pa.s over the applied shear rates. Finally, the thixoformed samples exhibited values of ductility and tensile strength superior to the as-cast and ECAPed samples
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Capps, Johnathon. "Advancements in vacuum process molding and casting." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Summer/master's/CAPPS_JOHNATHON_6.pdf.
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