Dissertations / Theses on the topic 'Aluminum Metallurgy'
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1
Dimayuga, Francisco Cruz II. "Vacuum refining molten aluminum." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72810.
2
Külünk, Bahadir. "Kinetics of removal of calcium and sodium by chlorination from aluminum and aluminum-1wt% magnesium alloys." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39752.
Abstract:
The kinetics of calcium and sodium removal at 730$ sp circ$C by chlorination from commercial purity (99.7% Al) and aluminum-1wt% magnesium alloys has been investigated. The contribution of chlorine containing gas bubbles, of intermediate reaction products generated by the chlorination process, as well as evaporation through the melt surface, to the removal of calcium and/or sodium has been documented quantitatively. Experimental parameters investigated were chlorine concentration in the gas bubbles and gas flow rate. The measurement of frequency of bubble formation at the tip of the gas bubbling nozzle enabled the surface areas of the bubbles to be estimated which in turn enabled melt phase mass transfer coefficients for the bubbles to be calculated.It was demonstrated that the removal of calcium and sodium followed first order reaction kinetics with respect to calcium and sodium concentrations. The removal of the above mentioned elements was represented well by a kinetic model in which mass transfer of sodium and calcium in melt phase was rate limiting.
In the case of the magnesium containing alloys, the MgCl$ sb2$ salt phase that was generated during chlorination was found to have a profound effect on the removal of calcium and sodium. The contribution of the salt phase to the removal of these elements was calculated to reach as high as 60%. In commercial purity aluminum, however, while the major contribution to the removal of calcium was from the chlorine containing gas bubbles, the major contribution to the removal of sodium was calculated to be evaporation of sodium through the melt surface.
3
Jaansalu, Kevin Michael. "Composites by directed oxidation of aluminum alloys." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60591.
Abstract:
The manufacture of ceramic composites has traditionally been a complex and often expensive process. A new processing method, the DIMOX$ sp{ rm TM}$ process, takes advantage of the high temperature oxidation behaviour of aluminum alloys to produce a ceramic-metal composite. Although this process is fairly simple to implement, there has not been any attempt to link the starting materials and manufacturing conditions to the properties of the final composite. This work attempts to identify some critical parameters in the manufacturing process and how they affect the end product. The reaction temperature, alloy composition, and powder bed condition were optimized with respect to the growth process, final composition, and resulting microstructure. These characteristics were then related to the elasticity, strength, fracture toughness, and fracture mode of the final composite.Aluminum-magnesium-silicon alloys were oxidized into an alumina bed of either Alcan C-70 UNG power or Struers' 400 grit. The process conditions were optimized in air at 1120$ sp circ$C with a 10% silicon, 2% magnesium alloy. The growth rate was dependent on the powder bed. The material was composed of alumina, silicon, aluminum, and trace amounts of magnesium aluminate spinel. The fracture mode was dependent on the composition of the material and the alumina bed.
4
Baik, Youngmin. "Carbothermal synthesis of aluminum nitride using sucrose." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60643.
Abstract:
In this work, the carbothermal reduction of Al$ sb2$O$ sb3$ to AlN was studied. Several kinds of aluminum oxides including $ alpha$-Al$ sb2$O$ sb3$, $ gamma$-Al$ sb2$O$ sb3$, $ theta$-Al$ sb2$O$ sb3$ and boehmite (AlOOH) were examined in order to observe the differences in reaction behaviour and powder characteristics obtained from each type of precursor. Cane sugar (sucrose) and carbon black were used as carbon sources. Reaction conditions studied were carbon to alumina ratio, temperature and reaction time. Sucrose resulted in a close-to-stoichiometric ratio of Al$ sb2$O$ sb3$:C (1:3.2) achieving full conversion to AlN and produced a regular powder morphology, whilst carbon black required higher ratio ($>$1:4) to reach full conversion with agglomeration of the AlN powder. The optimal reaction temperature was 1600$ sp circ$C with the reaction time being dependent on the Al$ sb2$O$ sb3$ source. The results of the thermodynamic study for the Al-N-O-C system suggest a solid-state reaction process which is consistent with the experimental observations. Moreover, flowing N$ sb2$ gas flushes out the product CO gas and thus forces the equilibrium in favour of AlN formation. Reaction mechanisms are proposed for the two forms of carbon precursor.
5
Tian, Chenguo. "Filtration of liquid aluminum with reticulated ceramic filters." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28932.
Abstract:
Fluid flow and filtration phenomena associated with filtration of liquid aluminum using reticulated ceramic filters were systematically investigated. It was found that fluid flow through this type of filter could be described by Darcy's Law up to a Reynolds number of 8, and the permeability of this type of filter ranged from about $9 times10 sp{-3}$ to $4 times10 sp{-2} rm mm sp2$.Parameters affecting filtration processes during the initial period were identified, some of which could be quantified numerically using a 2-D computational domain. According to these numerical analyses, the clean filter coefficient for this type of filter was linearly dependent on the dimensionless Stokes velocity of the suspended particles, had a $-$0.96 power dependence on the Peclet number, a $-$6.93 power dependence on the effective porosity of the filter, and exhibited only a weak dependence on the Reynolds number, in the Darcy velocity regime.
The dynamic behaviour of this type of filter was analyzed theoretically and simulated numerically using newly proposed correlations relating the filter coefficient and the pressure drop to the amount of particles captured within the filter (the specific deposit), and a model describing the morphology of captured particles. The simulated results showed that the filtration efficiency and the pressure drop increased with inlet particle concentration and filtration time; these increases were however, insignificant when the inlet particle concentration was less than 1 ppm for filtration periods of two hours, however, when the inlet concentration (initial and continued) reached 10 ppm, the change became appreciable.
Experimental data, obtained from liquid aluminum filtration tests conducted by the author in both laboratory and industrial settings, compared favourably with the numerical results.
6
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.
7
Hernández, Paz Juan Francisco. "Heat treatment and precipitation in A356 aluminum alloy." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19547.
Abstract:
Al-7%Si-0.3Mg (A356) foundry alloy is strontium modified and heat treated in order to obtain optimum mechanical properties. To date, the role that strontium modification plays in the precipitation process during the heat treatment is not well understood. The objective of the present work is to obtain a better understanding of the effect that strontium modification and heat treatment parameters exert on the properties of heat-treated Al-7%Si-0.3Mg alloy. The investigation consisted of a systematic measurement of the electrical conductivity and matrix microhardness of heat-treated coupons under different process conditions. Tensile properties were also measured and a transmission electron microscopy study of critical samples was done. The results obtained in this work indicate that the heat treatment of this alloy can be optimized. Solution heat treatment and artificial aging can be reduced and natural aging manipulated. The use of a continuous heating artificial aging is proposed. During the heat treatment of the A356 alloy under certain conditions not only does the precipitation of the Mg2Si occur, but also that of silicon. It was found that strontium modification does not influence the precipitation kinetics of the Mg2Si, but it does retard the precipitation of the silicon out of the matrix.
8
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.
Abstract:
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
9
Stephen, Gail. "Al-Fe-Si intermetallics in 1000 series aluminum alloys." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26424.
Abstract:
Iron and silicon are the major impurities in the 1000 series of wrought aluminum alloys. As the aluminum is recycled, it picks up more and more of these impurities which cannot economically be refined out of the aluminum. When the concentration of these impurities reaches a certain limit (maximum limit in 1000 series is 1 weight percent (Fe+Si)), the aluminum must be downgraded. The Fe and Si form brittle intermetallic phases in these alloys. The two main phases are the plate-like $ beta$-AlFeSi (Al$ sb5$FeSi) and $ alpha$-AlFeSi (Al$ sb8$Fe$ sb2$Si) which has a Chinese Script morphology. The mechanical properties of these alloys are believed to depend largely on the nature of these intermetallics.In the first part of this study, the conditions at which the intermetallics form, along with the ability of strontium to modify them were investigated. The second part consisted of determining how the morphology of the Al-Fe-Si phases affects the mechanical properties of the worked product. It was found that the formation of the Chinese Script morphology is promoted with increasing cooling rates, Fe/Si ratios and additions of strontium. However, the relative amount of Chinese Script was found to decrease with increasing (Fe+Si) levels. Tensile testing and formability testing (Erichsen ball punch deformation test) revealed that the presence of a Chinese Script morphology of Al-Fe-Si intermetallics (as opposed to the plate-like morphology) imparts no significant beneficial effect on the formability of the final rolled sheet.
10
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.
Abstract:
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.
11
Conte-Matos, Augusto. "The role of alloy composition and cooling rate from the melt on the dispersoid distribution in AA 6013." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/20208.
12
Jeniski, Richard A. Jr. "Recrystallization behavior of aluminum alloy 6013." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19412.
13
Fauré, Philippe L. "Aluminium : production processes and architectural application." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63919.
14
Paray, Florence. "Heat treatment and mechanical properties of aluminum-silicon modified alloys." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41146.
Abstract:
The commercial applications of cast Al-Si alloys depend to an important extent on controlling the morphology of the eutectic silicon through thermal modification in the solid state and/or chemical modification of the melt before the production of the casting. The effects of modification and/or heat treatment on the microstructure and the mechanical properties of 356 alloy have been investigated on both permanent mold and sand cast samples. Strontium (0.02%) and sodium (0.01%) were used to produce well modified microstructures. The importance of the amount of modifier used was also examined in producing castings with 0.002% Sr and 0.08% Sr. Production parameters such as solution heat treatment time and artificial aging time were examined.Microstructural assessment was done by quantitative metallography using image analysis coupled to SEM while mechanical testing comprised tensile testing, hardness and microhardness measurements as well as impact tests.
The greatest improvement in mechanical properties obtained with modification was observed for the lower rates of solidification, i.e sand casting. The effect of modification on the heat treatment response of 356 alloy was investigated. The differences between unmodified and modified microstructures were more important in sand cast samples than in permanent mold cast samples. After one hour of solution heat treatment at 540$ sp circ$C, both permanent mold unmodified and modified microstructures became similar in terms of silicon particle size and sphericity. The processes which led to this were different. Silicon platelets in the unmodified structures segmented while silicon particles in the modified alloy coarsened. The final result was however the same. In sand cast alloy, the initial microstructural differences persisted after up to 12 hours of solution treatment. The coarser the initial as-cast microstructure, the greater the improvements associated with modification and heat treatment.
It was also found that porosity caused by modification can negate many of the microstructural benefits by decreasing tensile strength and percent elongation. It was demonstrated that modification also has an influence on the aluminum matrix. The hardness of modified alloy was found to be less after the T6 temper than in unmodified alloy. This was reflected in a lower yield strength of modified 356 alloy.
Quantitative microstructure-mechanical property relationships were established for the permanent mold samples. The best silicon-structure characteristics to predict the tensile properties were found to be the particle count per unit area and the particle area.
It was also determined that hardness can be a simple and inexpensive means whereby ultimate tensile strength and yield strength of 356 alloy in the T4 condition or T6 condition can be estimated.
15
Shabestari, Saeed G. "Formation of iron-bearing intermetallics in aluminum-silicon casting alloys." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28920.
Abstract:
The formation of iron-bearing intermetallics in the 413 type of aluminum alloys was investigated comprehensively. Both synthetic and commercial 413 alloys were studied with iron concentrations in the range of 0.4-1.2 wt. % and manganese up to 0.5 wt.%. The effects of cooling rate during solidification and of melt chemistry on the morphology of iron intermetallic phases were determined. Image analysis was used to quantify the intermetallic size, volume fraction, and number, as a function of both melt chemistry and cooling rate. The total volume fraction of intermetallic compounds in these alloys was related to cooling rate by an exponential equation.The kinetics of both dissolution of intermetallics on melting, and of re-formation on cooling of the liquid were investigated by means of quenching experiments. Quantitative evaluation of intermetallic size and number revealed that the change in volume fraction of intermetallics in the liquid state is controlled by nucleation.
The effect of settling time and the rate of gravity segregation of intermetallic compounds in a stagnant liquid metal were investigated. It was found that, in the absence of convection, settling obeys Stokes' law with the terminal velocity reached at very short times and very close to the melt surface.
Strontium was used to modify or eliminate the iron-intermetallics. (Abstract shortened by UMI.)
16
Ragel, Kamal R. "Three dimensional modeling of vertical DC casting of aluminum alloys." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84313.
Abstract:
A three-dimensional mathematical model for the simulation of vertical direct chill (DC) slab casting of aluminum alloys has been developed. The model is based on the solution of the 3D time-averaged turbulent momentum (Navier-Stokes) and energy equations. The momentum equations are modified with a Darcy-type source term to simulate motion of the melt in the mushy region. The buoyancy force term is implemented in the model through the Boussinesq approximation. The low Reynolds number k-ε turbulence model of Launder and Sharma is used to calculate the Reynolds stresses and the turbulent heat fluxes. A variable heat transfer coefficient is used along the ingot surface to account for the different cooling regions. The mathematical model is qualitatively and quantitatively verified by comparing the computed results with a physical water model and a real casting experiment, respectively of independent researchers. Each of the comparisons showed a good agreement. The quantitative verification of the solidification front depths is improved when the thermal buoyancy force effect is included in the model.A parametric study has been carried on two casters of variable aspect ratio each using a different type of inlet melt distribution system. In the case of the small aspect ratio caster, the physical properties of aluminum Al-3104 are used. For this caster, the studied parameters are the casting speed, the primary cooling rate, the melt superheat and the combo-bag dimensions. Also, the effect of complete blockage of the bottom windows of the distribution bag is studied. An in-depth understanding of some behaviors of the melt flow and solidification profile in the steady state operational phase of the DC casting process is gained. For example, the roles played by the angle flow and the upward component of the vertical recirculation at the wide symmetry plane in controlling both the solidification front depth and the mushy layer thickness at the slab center are ascertained. This study has revealed the influence of the melt stream issued from the bottom window of the bag on the depth and uniformity of the solidification front. The model has successfully identified a faulty design of the short combo bag. This industrially favorite design causes what is called the reverse flow, that is, the melt from the surrounding sump enters the combo bag through the bottom window. (Abstract shortened by UMI.)
17
ALMEIDA, FILHO AMERICO de. "Elaboração e estudos de recristalização de ligas alumínio-magnésio-tório e alumínio-magnésio-nióbio." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11345.
Abstract:
Made available in DSpace on 2014-10-09T12:50:54Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:58:07Z (GMT). No. of bitstreams: 1 11108.pdf: 32426138 bytes, checksum: e0fd60a0b29703462d6537e5ea445860 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
18
Meratian, Isfahani Mahmood. "Thermal analysis of aluminum foundry alloys by a novel heat pipe probe." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28846.
Abstract:
A new application of heat pipes is introduced. The present research deals with the development of a heat pipe for the on-line quality control of liquid aluminum silicon foundry alloys.Thermal analysis is a technique whereby a small quantity of a melt is allowed to solidify while its cooling curve is recorded. Analysis of the cooling curve with standard mathematical algorithms allows one to determine a number of useful parameters that characterize the liquid and solid states of the material. In aluminum-silicon casting alloys thermal analysis is often used to assess the grain size and degree of eutectic modification of the alloy before pouring.
A novel probe has been developed for conducting thermal analysis of aluminum alloy melts. The probe, which resides in the melt, need not be withdrawn as it solidifies a small sample (i.e. button) at a predetermined cooling rate. Once the cooling curve results have been acquired, the probe can be instructed to remelt the frozen button and await instructions for analyzing a fresh sample.
The operating principle of this novel device is based on heat pipe technology. In simple terms, a heat pipe consists of a condenser and an evaporator which contain a relatively small quantity of working substance fluid. As heat is absorbed by the evaporator, the liquid phase of the working substance is vaporized and subsequently condensed on the condenser walls from which heat is extracted.
It has been shown that the designed probe, which is classified as a gas loaded annular thermosyphon, is completely workable in the range of conditions typically encountered in the thermal analysis of aluminum alloys. The thermal analysis results obtained with this new technique are in a good agreement with those of conventional thermal analysis. In addition, the new method is applicable to a wider range of operating conditions and is easier to use. Based on the semi-continuous nature of the new method, it does not need pre-preparation (materials, labour, pre-heating, thermocouple installation for each test, isolation of the sampling cup, etc.) to start thermal analysis. Also, from a cooling rate point of view, the system is well controllable. Moreover, it is shown that the probe is simple in construction, easy to use, and intelligent enough to provide semi-continuous thermal analysis. There are no consumable materials and moving parts.
Thermal analysis results are reported for pure aluminum, hypoeutectic aluminum silicon (356) and eutectic aluminum silicon (413) casting alloys. Agreement in the results between the new and conventional systems is shown to be excellent. Finally, a heat transfer/solidification model of the heat pipe thermal analysis probe is derived and validated.
19
Ozdemir, Ozgur. "Effect of strontium on the oxidation behavior of molten aluminum-magnesium alloys." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102689.
Abstract:
Magnesium additions to aluminum enhance strength and hardness, lowering density, and improve corrosion resistance. However, during melting and casting processes, significant amounts of magnesium are lost due to selective oxidation. Preventing these losses would reduce the production cost and improve the quality of the final product.The effects of various levels of strontium addition on the oxidation behaviour of aluminum-magnesium alloy melts were investigated by monitoring sample weight gains with time using a thermogravimetric balance at 750°C. Sample cross-sections have been examined in detail using Hitachi S-4700 Field Emission Gun Scanning Electron Microscope, and phases formed on the oxide layer and in the alloy morphology were identified by EDS, WDS and low angle X-ray diffraction techniques. It was observed that in the absence of Sr, the Al-Mg samples gained substantial amounts of weight by formation of spinel (MgAl2O4) phase at the oxide-metal interface. Samples containing Sr had significantly lower weight gains. The drop in total weight gain by Sr additions was about 98% in low Mg-containing Al-Mg alloys. This change in oxidation behavior was linked to the presence of a Sr-enriched liquid phase underneath the first formed MgO layer, suppressing the formation of spinel crystals. In addition, spherical equilibrium shapes are found in the different as-cast and oxidized alloys of Al-Mg-Sr.
20
Lee, Kitae 1966. "The influence of texture on the reliability of aluminum and copper interconnects /." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37759.
Abstract:
Texture in films develops during deposition processes and annealing of patterned wafers. Recent studies show that texture influences the performance and reliability of both aluminum and copper interconnects. To improve the current understanding of this matter, the influence of texture on reliability was studied.The influence of texture on electromigration and stress-induced failures in aluminum interconnects was studied since these are the most often responsible for failures observed in aluminum interconnects. Results obtained showed that a strong {111} texture in aluminum interconnects improves their median time-to-failure. The grain boundary character distribution and percentage of coincidence site lattice (CSL) boundaries, was quantified using orientation imaging microscopy. It was found that the median time-to-failure of specimens increased as the number of low angle and CSL boundaries increased. These boundaries are known to have low diffusivity. It was also demonstrated that while the investigated specimens had grains of comparable size, the grains of similar orientations were clustered in the specimens having the stronger {111} texture. This phenomenon contributed to the longer median time-to-failure of the interconnects by reducing the frequency of high angle grain boundaries. The experimental data obtained shows that the residual stress in films decreases as the intensity of the {111} texture increases. A model based on Monte-Carlo simulation of texture formation during the deposition of aluminum film was proposed to suggest the optimum conditions for a growth of a strong {111} texture component. A low deposition rate and a high mobility of atoms on the surface, which corresponds to a high substrate temperature, can strengthen {111} texture.
Copper has been recently used as an interconnecting material because of its good electromigration resistance and low electrical resistivity. One of the major problems of copper as an interconnecting material is that it easily oxidizes at relatively low temperatures. The formation of oxide degrades the electrical and mechanical properties of copper interconnects. The influence of substrate texture on the oxidation kinetics was studied to suggest methods to reduce copper oxidation. Copper single crystals having (100), (110), (123), (314), (111) and (311) orientations were oxidized at 200ºC in air. Only the Cu2O phase was formed during oxidation. The oxidation of the (100) single crystal substrate was much faster than that of the others. This is attributed to a large number of fine oxide grains on the (100) crystal in the initial stages of oxidation. It is recommended that the {100} texture in copper interconnects should be avoided in order to reduce oxidation rate. A quantitative model was proposed to predict the oxidation kinetics of copper from the texture of the specimens. Reasonable agreement was obtained comparing the model predictions and the experimental results obtained from the test of oxidation of polycrystalline copper specimens. However, further improvement of the model can be done if more data from single crystal experiments are obtained.
21
Dennis, Keith. "Effects of magnesium, silicon, and strontium on the oxidation of molten aluminum." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0018/MQ55020.pdf.
22
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:
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.
23
La-Orchan, Wittaya. "Melt treatment effects on porosity and impact strength in hypoeutectic aluminum silicon alloy." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22446.
Abstract:
The effects of the three factors (modification, grain refinement, and hydrogen level) on the amount of porosity, impact strength, and performance of the reduced pressure test in A356 alloy have been studied. It was found that grain refinement, acting singly and in combination with modification, reduces the porosity by inducing mass feeding. However, this beneficial effect may not be found at all cooling rates and casting sizes. There is less total shrinkage in Sr-alloyed samples than in those which are non Sr-alloyed. The reason for this is supposed to be a difference in the liquid density which may be higher in Sr-alloyed samples. Modification has the strongest effect on improving the impact strength of A356 alloy. Hydrogen reduces it slightly. On the other hand, grain refinement, acting singly or in combination with modification, was not found to improve the impact strength of the alloy. To obtain optimum impact strength, it is recommended that a combination of modification and degassing to about 0.1 ml.H$ sb2$/100 g. Al. be used. An excellent linear relatiosnhip between density and hydrogen level exists for all combinations of melt treatment processes when the redued pressure test is used. Three methods of predicting the true hydrogen level are proposed and calculated hydrogen levels agree reasonably well with measured melt hydrogen within the error range of $ pm$0.05-0.1 ml./100 g. Al.
24
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.
Abstract:
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.
25
Chang, Sin-ting Cynthia. "Randomization of recrystallization textures in an experimental Al-5%Mg alloy and AA6111." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36375561.
26
Wang, Yongqing. "Aluminide coatings on Fe-9Cr-1Mo steel synthesized by pack cementation for power generation applications : a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online version, 2006. http://proquest.umi.com/pqdweb?index=89&did=1260818241&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1255459401&clientId=28564.
27
Chang, Sin-ting Cynthia, and 張倩婷. "Randomization of recrystallization textures in an experimental Al-5%Mgalloy and AA6111." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36375561.
28
Yuen, Pui Kei 1976. "Effects of strontium on the oxidation of molten aluminum alloys containing silicon and magnesium." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34004.
Abstract:
In the presence of air and oxygen, oxidation of a molten aluminum alloy will easily take place. The oxidation not only harms the operation by contributing to melt losses, but the processing of the oxides present in the melt and refractory is also costly in time and money. Refractory accretions formed due to the interactions between the oxide-layer and base refractory material, especially alumina-lined ones, are a significant problem for the industry. Aluminum alloys containing magnesium are known to oxidize much more easily and rapidly. In the foundry, oxidation of molten aluminum-magnesium alloy is more prominent than that of pure aluminum. Magnesium has a higher affinity for oxygen, causing it to oxidize more easily than aluminum. In previous studies of oxidation of aluminum alloys, it has been found that strontium additions to the alloy reduce the amount of oxidized layer in an undisturbed melt.The effects of strontium additions on the oxidation behavior of commercial A356, A357 and 5182 aluminum alloys were investigated by monitoring sample weight gains with time with a thermo-gravimetric balance at 700, 750, and 800°C. Sample surfaces were examined using electron microscope and x-ray diffraction techniques. It was found that in the absence of Sr, the A356 and A357 samples gained substantial amounts of weight through the preferential oxidation of magnesium. Samples containing strontium had significantly lower weight gains. For the high magnesium-containing 5182 alloy, an increase of incubation period before the onset of significant oxidation is associated with the presence of strontium. This change in oxidation behavior was linked to the presence of strontium containing oxide species in the oxidizing surface.
29
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.
Abstract:
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.
30
Silva, Beethoven Max Alves da. "Influencia da microestrutura inicial e material de molde na tixoconformação da liga A356." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263687.
Abstract:
Orientador: Maria Helena RobertDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho investiga-se a influência da microestrutura inicial e do material do molde na tixoconformação da liga A356. São produzidas e testadas em operações de tixoforjamento pastas obtidas por três distintos processos: fusão parcial controlada de estrutlJ'aS dendríticas grosseiras, fusão parcial controlada de estruturas ultra-refinadas e pastas obtidas por agitação mecânica do líquido durante solidificação. É produzido ainda um compósito A356 + Ab03 obtido por compofundição. Os tixoforjados foram submetidos à análise metalográfica para caracterização microestrutural, medindo-se a fração da fase primária e o tamanho médio de glóbulo ou roseta da fase sólida. Os resultados obtidos mostram a viabilidade da utilização de moldes não metálicos e operações de tixoconformação com produtos de bom acabamento superficial e dimensional. As forças de tixoforjamento são dependentes da condição inicial da matéria-prima, de forma que forças maiores são requeridas com o aumento do parâmetro microestrutural básico (espaçamento interdendrítico, tamanho de glóbulo e tamanho de roseta) da matéria-prima
Abstract: This research aims the influence of initial microstructure and die material on thixofonning of A356 alloy. Obtained slurries are produced and tested in thixoforging operation by three distinct processes: controlled partial melting of coarse dendritic structures, controlled partial melting of ultra-refined structures and obtained slurries by liquid mechanical stirring during solidification. It is still produced a composite A356 + AbO:i obtained by compocasting. Thixoforged samples were submitted to metalographic analysis for microstructural characterisation, measuring the primary phase fraction and globule average size or 50lid phase rosette. Obtained results showed the viability of non-metallic dies in thixoforming operations with good superficial and dimensional finishing produds. Thixoforging forces are dependent on initial condition of raw material, 50 that higher forces are required with the increasing of basic microstructural parameter Onterdentritic spacing, globule size and rosette size) of raw material
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
31
Samuel, Ehab. "Serrated flow and enhanced ductility in coarse-grained Al-Mg alloys." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115867.
Abstract:
Aluminum 5XXX alloys are of industrial importance and interest as they combine a wide range of desirable strength, forming and welding characteristics with a high resistance to corrosion. The presence of Mg in these alloys ensures favorable mechanical properties. However, the room temperature stretching performance of these alloys is limited. Moreover, Al-Mg alloys are known for being susceptible to the Portevin-LeChatelier effect when deformed at room temperature. Nevertheless, improvements in ductility can be achieved through warm forming, especially when the ductility approaches superplastic levels.The aim of this study was to test for enhanced ductility in three coarse-grained Al-Mg alloys namely, super-pure Al-3%Mg and Al-5%Mg, and commercial AA 5056 alloy. The temperature-dependent flow stress and rate sensitivity behavior of these alloys was investigated by means of tensile testing using ASTM E8M-04 standard samples. Samples were deformed to 10% strain to allow enough deformation to occur such that serrations in the dynamic strain aging (DSA) temperature/strain rate range would be rendered visible on a stress-strain curve. Using this information, the regions of negative and higher-than-normal strain rate sensitivity ('m') were plotted and tensile tests to failure were performed in the vicinity of maximum 'm'. ASTM E2448-06 standard samples for superplasticity tensile testing were used in this case.
A maximum ductility of 170% was recorded with these samples and this was found to increase to nearly 300% when the gage length was shortened. It was observed that the DSA serrations were more prominent at lower strain rates, higher temperatures and higher Mg contents. The results of this study show clearly that if the rate sensitivity is high enough, then enhanced ductility in coarse-grained materials is possible at temperatures well below the maximum test temperature.
32
Park, Conrad. "Mechanical Performance and Structure-Property Relations in6061B Aluminum Metal Matrix Composites." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1547842396716777.
33
Knittel, Susan Means 1961. "Sintering of aluminum-nitride in a microwave induced plasma." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276877.
Abstract:
The sintering of aluminum nitride in a microwave induced plasma was investigated. The plasma furnace consisted of a quartz tube inserted into a waveguide connected to a 2450 MHz microwave generator. After evacuating the tube to about 1.33 mbar, nitrogen gas was introduced, generating a steady plasma. Processing parameters such as gas pressure, power level, and time were optimized to yield maximum densification of aluminum nitride. Sintering of pure and doped AlN compacts was performed in the nitrogen plasma at temperatures up to 2000 S C. Undoped specimens reached densities of only 81% theoretical, while densities in excess of 95% theoretical were achieved for yttria doped specimens in less than 15 minutes. Microstructural investigations revealed a smaller grain size in the plasma sintered specimens (about 2μ) than are present in conventionally sintered AlN (about 8μ).
34
Wang, Ganlin. "Effect of aluminum on recrystallization and precipitation of Nb HSLA steels." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65336.
35
Weinberg, Jonathan David 1966. "Geometrical and computational modelling of grain boundaries in aluminum." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277888.
Abstract:
This study presents an integrated approach using experimental high resolution electron microscopy, computer simulations and theoretical analysis, to provide a thorough atomic level investigation of grain boundaries. Examined here, are specific cases of pure aluminum grain boundaries. Energy calculations for the Sigma3 perfect twin, in a range of linear translational states, show that both the shape and location of the interfacial surface are important considerations.
36
Blaskovich, Timothy D. "Computational modelling of an electromagnetic system for separation of solid inclusions from molten aluminum." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33958.
Abstract:
Mathematical models and numerical solution methods for the computer simulation of solid particle trajectories in flows of molten aluminum subjected to steady, uniform, electric and magnetic fields are presented in this thesis. The underlying subject is electromagnetic (EM) filtration of molten metals.Attention is focused on steady, laminar, fully developed flows of molten aluminum inside a straight separation chamber of uniform rectangular cross-section. The walls of this chamber are assumed to be electrically non-conducting. The investigation is limited to solid inclusions (particles) that are electrically non-conducting and have an effective diameter in the range 5 mum to 100 mum. Steady, uniform, electric and magnetic fields are prescribed, and the induced currents are assumed to be negligible.
Mathematical models of three-dimensional parabolic (developing) and fully developed flows of molten aluminum in the separation chamber are provided, nondimensionalized, and discussed. A rudimentary model of the magnetohydrodynamic (MHD) flow is proposed, in which Maxwell's equations are decoupled from the Navier-Stokes equations. The particle momentum equation is presented, nondimensionalized, and discussed in detail.
The fluid flow problem is solved using a control-volume finite element method (CVFEM). The particle momentum equation is solved using a fourth-order Runge-Kutta (RK) method. An efficient method is proposed for locating the particle in the finite element mesh during the RK integration of the particle momentum equation.
The proposed methods are applied to four test problems, and the results are compared to those obtained using analytical and numerical solutions available in the literature. Finally, the scope of the proposed methods and some of the possibilities they offer are explored by applying them to a simple electromagnetic system for the separation of solid inclusions from molten aluminum.
37
Cinkilic, Emre. "Alloy Design and Precipitation Modeling of High Fe Concentration Recycled Cast Aluminum Alloys for Structural Applications." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555599698005398.
38
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:
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.
39
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.
Abstract:
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.
40
Seifi, Seyed Mohsen. "Mechanical Property Evolution and Thermal Remediation of Aluminum Magnesium 5xxx Alloys Following Low and Intermediate Temperature Thermal Exposure." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1365507691.
41
Hinton, Kimberly D. "Extended heat treatment effects on the fracture toughness of cast aluminum alloy A357." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/17361.
42
Barker, Simon William. "Diffusion induced liquid film migration in the aluminum-copper system /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/NQ42721.pdf.
43
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/.
Abstract:
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.
44
Zhang, Bin. "Fatigue behavior in an aluminum casting alloy (A356.2): Effects of some defects, SDAS, Hipping and strontium modification." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280228.
Abstract:
Effects of pore, secondary dendrite arm spacings (SDAS ), hot isostatic pressing (Hipping), and strontium-modification on fatigue behavior were studied in an aluminum casting alloy (A356.2). Microstructures were revealed by X-ray radiography, light microscopy and scanning electron microscopy. Small-cracks were monitored by taking replicas of the surfaces with which the cracks intersected. As the SDAS increases from 15 to 55 μm, fatigue life decreases by a factor of 3 in low-cycle fatigue, and 100 in high-cycle fatigue. When SDAS is less than 30 mum, the pore size is below a critical size of ∼80 μm and large eutectic constituents initiate cracks; and the initiation life is as high as 70% of the fatigue life. As the SDAS increases beyond 30 μm, pores are the main crack-initiation sites; the initiation life is as low as 5% of the fatigue life. Near-surface oxides initiate the fatigue crack regardless of SDAS. When crack initiated at pore and oxides, fatigue life is well correlated with the size of the initiation site and the effect of SDAS is overshadowed by the effect of pore. Non-hipped A356.2 without Sr shows better fatigue life and the deleterious effect of pores overshadowed the beneficial effect that Sr-modification might have had. Hipping significantly increased the initiation life and small-crack propagation life of A356.2 with Sr as a result of the elimination of the porosity. However, hipping did not significantly improve the fatigue life of A356.2 without Sr. After hipping, Sr-modification is beneficial in improving the crack initiation life, and increasing both small-crack and long-crack propagation lives. Fracture mechanics models (Newman-Raju, and Trantina-Barishpolsky models) yielded similar results on the crack-propagation rate against the effective stress-intensity factor range. In the micro-mechanics model, the theory of continuously distributed dislocations was applied to represent crack and crack-tip plastic zone, and the propagation rate was related to the length of the crack-tip plastic zone. When the grain size is used as the characteristic length of the microstructures, the model predicts the oscillations of the propagation rates and the predicted rates agreed reasonably well with those from experiments.
45
Thanaboonsombut, Buncha. "Microstructural evolution and recrystallization modeling in AA6013 and compositional variants of 6013." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/20020.
46
Priest, Matthew. "Synthesis of reactive element-modified aluminide coatings on single-crystal Ni-based superalloys by a pack cementation process a thesis presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2009. http://proquest.umi.com/pqdweb?index=26&did=1760523421&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1254926883&clientId=28564.
47
Sivertsen, Halses Sebastian. "Die life prediction using High Pressure Die Casting simulations." Thesis, Tekniska Högskolan, Jönköping University, JTH, Material och tillverkning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-50031.
Abstract:
Global trends in automotive industry for weight reduction drives an interest for casting of structural aluminum parts. High pressure die casting (HPDC) is chosen for this purpose since it enables manufacturing of large series parts where complexity and repeatability is demanded. Aluminum alloys have hence been developed through the years to obtain suitable mechanical properties for high strength parts. These alloys have been investigated to predict the types of potential failure mechanisms during HPDC in order to determine die life through simulations. Die life prediction was performed through simulations in MAGMAsoft 5.4 with the help of a die life module, which is based on thermal stresses generated in the die material during casting cycles. Fatigue data at elevated temperature obtained from literature review of AISI H11 tool steel was complemented to the Wöhler curve in the software database. Comparison of two aluminum alloys showed that chemical composition had a major influence on die life. Chemical composition had a direct impact on solidification time and with longer solidification time, the thermal load on the die increased. Since the stress range on the die is temperature dependent, the ability of heat transfer over time proved to be critical for die life results. The most crucial process parameter to achieve a longer die life was constant cooling by tempering channels, due to their high potential to remove heat. Tempering channels and die spray also prevent the die from exceeding a critical temperature resulting in soldering formation. Mold erosion was consistently observed in the same location for all simulations.
48
Sen, Fatih Gurcag. "Non-equilibrium Molecular Dynamics Of Electromigration In Aluminum And Its Alloys." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607654/index.pdf.
Abstract:
With constant miniaturization of integrated circuits, the current densities experienced in interconnects in electronic circuits has been multiplied. Aluminum, which is widely used as an interconnect material, has fast diffusion kinetics under low temperatures. Unfortunately, the combination of high current density and fast diffusion at low temperatures causes the circuit to fail by electromigration (EM), which is the mass transport of atoms due to the momentum transfer between conducting electrons and diffusing atoms. In the present study, the effect of alloying elements in aluminum on the diffusion behavior is investigated using a non equilibrium molecular dynamics method (NEMD) under the effect of electromigration wind force. The electromigration force was computed by the use of a pseudopotential method in which the force depends on the imperfections on the lattice. 1.125 at% of various elements, namely Cu, Mg, Mn, Sn and Ti were added into aluminum. The electromigration force was then calculated on the alloying elements and the surrounding aluminum atoms and these forces incorporated into molecular dynamics using the non-equilibrium formalism. The jump frequencies of aluminum in these systems were then computed. Cu,
Mn and Sn impurities were found to be very effective in lowering the kinetics of the diffusion under electromigration conditions. Cu was known experimentally to have such an effect on aluminum for several years, but the Mn and Sn elements are shown here for the first time that they can have a similar effect.
49
Demirel, Onur. "Development Of Automobile Chassis Parts Via Aluminum Extrusion And Sand Casting Technology." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614965/index.pdf.
Abstract:
Due to the environmental issues related with fuel consumption and additionally passenger safety, aluminum space frame chassis is promising a big opportunity to design a lightweight structure with a high stiffness. Despite the lower stiffness and strength of aluminum in comparison to the conventional steel chassis, it can be compensated with changing thickness and design of structure by space frame geometry In this study, instead of using steel for automobile chassis, main goal is producing a space frame structure with using aluminum in an extrusion and sand casting processes and improve the stiffness. Chassis is designed according to calculations for moment of inertia, torsional and bending stiffness and in sufficient structural stiffness which can compete with steel chassis. Static finite element analysis was carried out to understand the chassis bending, torsional stiffness and fatigue behaviors. For frontal collisions, dynamic finite element analysis was also done to determine increases in the energy absorbance, specific energy absorbance and peak force for passenger safety. Aluminum profiles were produced by hot extrusion and joined with sand casting parts by TIG welding to manufacture a space frame structure. For main chassis profile, 6063 series of aluminum alloy was selected due to availability for extrusion process, weldability and having sufficient tensile strength and percent elongation and treatment response. Three point bending test was carried out to determine flexural strength. Moment of inertia calculations were done. Some parts such as side frame and shock absorber tower were produced by sand casting method. A similar composition to Silafont &ndash36 aluminum alloy was selected because of its high fluidity and good mechanical properties
despite it is a die cast alloy. Tensile, hardness and Charpy impact test were conducted to determine the mechanical characteristics of Silafont - 36 sand cast alloy. In addition to microstructure features and thermal analysis were also carried out to achieve sufficient alloy properties. Heat affected z one was investigated by hardness and tensile test to determine the mechanical properties change after welding process. In this space frame development study, A, B and C pillar parts were produced by Al &ndash
Si sand casting and T6 heat treatment then welded together by TIG welding and finally assembled on the bottom chassis frame produced by using 6063 extrudes welded by 4000 series electrodes. The space frame chassis was studied by also computer simulation to test and see critical points which must be modified during manufacturing. Besides the experimental and theoretical studies, space frame was also produced at the same time. According to the experimental results, the feasibility of the production of lightweight and solid chassis structure was achieved.
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Anderson, Danny. "Effect of the joint addition of aluminum and molybdenum on the precipitation and recrystallization in HSLA steels." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66207.