Дисертації з теми "Casting alloys"
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1
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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Keeble, J. M. "Grain refinement of A17Si shaped casting alloys." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637769.
Повний текст джерелаАнотація:
An investigation was undertaken to clarify the effects of various grain refiners on primary grain size of A17Si type alloys. By observing the influence of master alloy grain refiners containing B, Ti, Ti and B, and Ti and C under controlled casting conditions (constant holding temperature of 750°C, cast into graphite moulds held at room temperature) with variations in holding time, addition levels and Ti:B ratios, it was possible to achieve a greater degree of understanding as to the required additions to attain desired refinement levels in the casting house. Two types of test were carried out. Firstly, two minute grain refiner tests, where the samples were taken from the melt two minutes after grain refiner addition. These tests were used to establish the effects of; increasing Si content from 0 to 7wt% (in the absence of grain refiner and with grain refiner additions of Al-Ti and A15Ti1B at a number of addition levels) and increasing addition level of Ti, B, Ti and B, and Ti and C on the primary grain size of A17Si. The second type of test established the influence on grain refinement, using additions of Ti, B, Ti and B, and Ti and C, of various holding times up to two hours. The effect on grain size of varying Ti:B ratio was also studied using master alloys containing both Ti and B with various ratios and also by making additions of Al-Ti and A1-B refiners. From the fade tests it has been found that, with additions of A1-Ti refiners, levels of Ti above the peritectic TiA13 level give best refinement with virtually no fade observed at any of the additional levels studied. For the two addition levels of AlTiC studied, grain size increases over holding time and decreases on stirring the melt after the two hour holding period, suggesting some nucleant particle settling. With Ti and B containing refiners, those with ratios of Ti to B < 2.2:1 produce finer primary grains sizes at given B levels with a reduced tendency to fade. Addition levels of 0.02wt%B or more produce finer grain sizes than lower addition levels due to increased numbers of nucleants, reducing observed effects of nucleant settling by ensuring sufficient B containing particles are in the melt to achieve adequate grain refinement even after a two hour holding period.
3
Saleem, Muhammad Qaiser. "Helium Assisted Sand Casting of Aluminum Alloys." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/204.
Повний текст джерелаАнотація:
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.
4
Kalkanli, Ali. "Investigations of melt overflow of alloys." Thesis, Open University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293674.
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5
Pan, Qingyu. "Green & Clean Al-Cu Alloys." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1273.
Повний текст джерелаАнотація:
For aluminum alloy casting, degassing is a necessary step for molten metal, which can extract the dissolved hydrogen in the melt. For copper-containing aluminum alloys, a traditional method is that using the mixed gas of inert gas and chlorine as the degassing agent. Because of the toxicity of the gaseous chlorine, the industrial is trying to avoid using it even though this method can contribute to good castings. As a potential solution, the foundry only used argon during degassing, however, the castings with this method were unacceptable since the occurrence of defects.
The goal of this project is to develop a new green and clean degassing method for copper- containing alloys without the usage of gaseous chlorine. To achieve this goal, identify those defects and figure out the source of those defects are necessary. Totally four hypotheses of the occurrence of defects were supposed and two of them were discussed in this thesis. They are ineffective hydrogen removal and metal-mold reaction. Experiments were set in WPI and Palmer Foundry to investigate defects from samples with different conditions. This thesis collected and discussed the results from experiments, and made the conclusion that whether these two hypotheses contribute to the occurrence of defects.
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.
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7
Musson, Nicholas John. "The squeeze casting of aluminium alloys and composites." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293609.
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8
Cheng, Xu. "Inert refractory systems for casting of titanium alloys." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3838/.
Повний текст джерелаАнотація:
Research has been undertaken to develop new yttria slurry systems for use in mould face coats for investment casting TiAl alloy, solving the pre-gelation problems of commercial yttria slurry systems to increase slurry life. Meanwhile, the new face coats should also have excellent sintering properties, chemical inertness, surface finish and be easy to prepare. The processes of developing the new slurry started with the filler powder investigation by adding different sintering additives into the yttria powder to achieve good sintering properties. Then the best filler powder candidates were selected to make the slurry. Finally, the new face coat slurries were used to make the shell face coat and the chemical inertness of those shells were investigated through the sessile drop and investment casting. In the research, the filler powder and face coat sintering properties were quantified through density, dilatometer testing, X-ray diffraction (XRD) and microstructural change at different testing temperatures. The interaction of different face coat systems and the metal were identified using hardness tests, sessile drop contact angle and the microstructural change at the metal/shell interface. In this research, three water-based binder face coat systems containing YF\(_3\), Y\(_2\)O\(_3\)+0.5wt% Al\(_2\)O\(_3\)+ 0.5 wt% ZrO\(_2\) (YAZ), and B\(_2\)O\(_3\) additives were found to have similar or even better sintering properties compared to a commercial face coat. Meanwhile, they had long life.
9
Maeder-Siryj, Agnes. "Inhibition of cell proliferation by dental casting alloys /." [S.l.] : [s.n.], 2001. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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10
Deez, Brent Steven. "An investigation on the suitability of layer manufacturing methods for rapid tooling development in investment casting of light metal alloys." Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/2228.
Повний текст джерелаАнотація:
Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010.The research presented in this report focuses on Investment Casting capabilities for light metal alloys in South Africa and forms part of the Advanced Manufacturing Technology Strategy's (AMTS): Light Weight Metals flagship programme. The research is centred on the suitability of rapid prototyping (RP)/Iayer manufacturing (LM) methods to produce patterns for the investment casting of aluminium (AI), magnesium (Mg) and titanium (Ti) alloys, together known as Rapid Investment Casting. Three core RP technologies are investigated namely: Three Dimensional Printing - Drop-on-Bed from Z-corporation, Three Dimensional Printing - Drop-on- Drop from ThermoJet - 3D Systems and Selective Laser Sintering from EOS. Various RP/LM processes are discussed in detail and highlight the technologies selected in this study. A standard benchmark part, adapted from the European project framework FP6, designed and utilised in similar studies is used as the basis for the research. The Investment Casting process is discussed fully and compared to the Rapid Investment Casting, listing both the advantages and disadvantages of the above mentioned methods. In addition a special study has been conducted on investment casting of large components using layer manufactured patterns. This study not only helped to establish and validate the shrinkage value calculated for the aluminium castings but also showed substantial capability lacks in SA foundries to handle this type of components, which are by definition most often of high added value.
11
Sjölander, Emma. "Heat treatment of Al-Si-Cu-Mg casting alloys." Doctoral thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Material och tillverkning – Gjutning, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-15695.
Повний текст джерелаАнотація:
Environmental savings can be made by increasing the use of aluminium alloys in the automotive industry as the vehicles can be made lighter. Increasing the knowledge about the heat treatment process is one task in the direction towards this goal. The aim of this work is to investigate and model the heat treatment process for Al-Si casting alloys. Three alloys containing Mg and/or Cu were cast using the gradient solidification technique to achieve three different coarsenesses of the microstructure and a low amount of defects. Solution treatment was studied by measuring the concentration of Mg, Cu and Si in the α-Al matrix using wavelength dispersive spectroscopy (WDS) after various times at a solution treatment temperature. A diffusion based model was developed which estimates the time needed to obtain a high and homogenous concentration of alloying elements for different alloys, temperatures and coarsenesses of the microstructure. It was shown that the yield strength after artificial ageing is weakly dependent on the coarseness of the microstructure when the solution treatment time is adjusted to achieve complete dissolution and homogenisation. The shape and position of ageing curves (yield strength versus ageing time) was investigated empirically in this work and by studying the literature in order to differentiate the mechanisms involved. A diffusion based model for prediction of the yield strength after different ageing times was developed for Al-Si-Mg alloys. The model was validated using data available in the literature. For Al-Si-Cu-Mg alloys further studies regarding the mechanisms involved need to be performed. Changes in the microstructure during a heat treatment process influence the plastic deformation behaviour. The Hollomon equation describes the plastic deformation of alloys containing shearable precipitates well, while the Ludwigson equation is needed when a supersaturated solid solution is present. When non-coherent precipitates are present, none of the equations describe the plastic deformation well. The evolution of the storage rate and recovery rate of dislocations was studied and coupled to the evolution of the microstructure using the Kocks-Mecking strain hardening theory.
12
Moffat, Andrew James. "Micromechanistic analysis of fatigue in aluminium silicon casting alloys." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/52400/.
Повний текст джерелаАнотація:
Due to increasingly stringent environmental legislation, there is a requirement for lower emissions and greater overall efficiency of light vehicle diesel (LVD) engines. This continues to be achieved through the optimisation of design and careful selection of the materials used in key LVD engine components, for example pistons, so that they are lighter and can operate at higher temperatures. Pistons are non-serviceable parts and so must be able to withstand the fatigue and high temperature environment of the car engine. It is therefore important to understand the mechanisms of fatigue in these alloys to help inform alloy development for the next generation of pistons. Pistons are typically produced from multi-component Al-Si casting alloys. These alloys exhibit a complex, multiphase microstructure comprising α-aluminium as the matrix with silicon particles and several intermetallic phases. Previous research on Al-Si casting alloys has demonstrated that porosity is detrimental to fatigue life as cracks initiate freely at pores. However, with improved casting techniques porosity can be greatly reduced and other microstructural features influence fatigue life. In particular, Si particles have been shown to play an important role in the initiation and subsequent propagation of fatigue cracks. This study assesses the role of Si content and other microstructural features on fatigue behaviour by testing a set of well-characterised multi-component, Al-Si casting alloys with varying Si content. Fatigue initiation behaviour was investigated at room temperature using S-N and short fatigue crack growth experiments. Pores, Si particles and intermetallic phases were shown to cause fatigue crack initiation. In a 0.67wt% Si containing alloy, large-scale porosity was observed and was the foremost reason for fatigue initiation. In two alloys the Al9FeNi phase was observed to be the most detrimental hard particle causing fatigue crack initiation. Nanoindentation results showed that Al9FeNi had a lower hardness and higher modulus than Si and so Al9FeNi may be expected to fracture preferentially, consistent with the fatigue results. X-ray computed tomography demonstrated that all the alloys investigated contained a complex, interconnected, intermetallic sub-structure. As a result, the micromechanisms of fatigue are different to those in conventional particulate Al-Si alloys because particle fracture is required to ensure a level of crack continuity. At room temperature and 350˚C, and at low and high crack growth rates, the crack tip may be described as a diffuse region of micro-damage and intact ligaments. It is the extent of this damage in the alloys that controls the crack growth rates exhibited and simple trends between the Si content and roughness, reported for particulate systems, do not hold true in the alloys investigated in this study. The balance of the micromechanisms of fatigue was shown to be dependent on temperature. This highlights the importance of fatigue studies at temperatures that are characteristic of those experienced in service.
13
Cisternas, Fernández Martín Matías. "Modeling of solidification of TiAl alloys in centrifugal casting." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0218.
Повний текст джерелаАнотація:
Les alliages TiAl sont un groupe de matériaux important pour les industries automobile et aérospatiale, de par leur faible densité et bonne tenue mécanique à haute température. Cependant, à cause de leur forte réactivité à l’état liquide, au moment de couler ces alliages, il faut utiliser une faible surchauffe pour limiter la contamination. La coulée centrifuge est une option pour améliorer le remplissage du moule à faible surchauffe. En coulée centrifuge, l’effet de la poussée d’Archimède sur le mouvement du liquide est renforcé, ce qui modifie l’écoulement par l’effet combiné de la force centrifuge et de force de Coriolis qui apparaissent dans le système en rotation. Ceci fait que des motifs particuliers de macroségrégation et de distribution de microstructures se forment dans la pièce solidifiée, et l’origine de ces motifs n’est pas très bien comprise. L’objectif de cette thèse est d’expliquer l’écoulement du liquide ainsi que le transport des grains solides et des espèces chimiques pendant la solidification d’alliages TiAl en coulée centrifuge. Un modèle 3D volume finis de solidification multi-échelle a d’abord été développé dans le cadre de cette thèse. Un tel modèle était nécessaire à cause de la nature tridimensionnelle des écoulements. Le modèle a ensuite été utilisé pour simuler des essais expérimentaux de solidification dirigée d’échantillons cylindriques en alliage TiAl GE (Ti-47Al-2Cr-2Nb), précédemment réalisés dans le cadre du projet ESA GRADECET. Ces essais ont été réalisés dans la “Large Diameter Centrifuge” de l’ESA, à des intensités de centrifugation entre 5g et 20g, où g est l’accélération standard de la gravité terrestre. Les résultats des simulations montrent que la force de Coriolis modifie complètement l’écoulement du liquide pendant la solidification, résultant en une unique boucle de convection dans le bain liquide. Inversement, la force de Coriolis n’a qu’un faible effet sur le mouvement des grains équiaxes. A forte centrifugation, le mouvement des grains est surtout gouverné par l’équilibre entre la gravité apparente et la force de trainée. Les résultats montrent aussi que la macroségrégation finale de l’aluminium n’est pas symétrique et présente un fort enrichissement le long du bord d’attaque de l’échantillon. Ceci est dû à l’asymétrie de l’écoulement induite par la force de CoriolisTiAl alloys are an important material for automotive and aerospace industries due to their low density and high strength at high temperatures. However, due to their high reactivity in liquid state, low superheat must be used in casting in order to limit contamination. Centrifugal casting is an option to enhance mold filling at low superheat. In centrifugal casting the buoyancy driven flow is intensified and the flow structure is modified by the combined effect of the non-inertial accelerations – centrifugal and Coriolis – which appear in the rotating system. The consequence are particular patterns of macrosegregation and of distribution of microstructures in the solidified part. These patterns are not well understood. The objective of this thesis is to explain the flow structure, as well as the transport of solid grains and of chemical species during solidification of TiAl alloys in centrifuged systems. In the framework of this thesis a 3D finite-volume implementation of a multiscale solidification model was developed, which was required due to the inherently three-dimensional nature of the flow. The model was then used to simulate dedicated experiments of directional solidification of cylindrical samples of the TiAl GE alloy (Ti-47Al-2Cr-2Nb) that were previously conducted in the frame of the ESA GRADECET project. These experiments were carried out in the ESA “Large Diameter Centrifuge” at centrifugation levels between 5g and 20g, where g is the normal terrestrial gravity acceleration. The results of the simulations show that the Coriolis acceleration entirely modifies the liquid flow structure during solidification and lead to a one-vortex fluid flow pattern in the domain. On the contrary, it is shown that the Coriolis acceleration has only a weak impact on the motion of equiaxed grains. At high gravity level the grain motion is mainly controlled by the balance between the apparent gravity and the drag force. It is also shown that the final aluminum macrosegregation pattern show a strong enrichment on the flight velocity side of the sample due to the asymmetry of the liquid flow induced by the Coriolis force
14
Mackie, David. "Characterisation of casting defects in DC cast magnesium alloys." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-casting-defects-in-dc-cast-magnesium-alloys(427257fa-04b3-46a3-9128-d21a79f3078a).html.
Повний текст джерелаАнотація:
The continued interest in the use of magnesium alloys for new applications demand the successful production of high quality wrought alloys. Magnesium Elektron seek to reliably produce high quality alloy billets by the DC casting method combined with ultrasonic inspection. The main objectives of this study are to characterize the defects which are currently found in the material and to understand the ability of the ultrasonic inspection technique currently employed to detect the defects. This study began by locating defects using the ultrasonic inspection method which were then characterised using X-ray Computed Tomography (XCT) 3D imaging technique. Attempts were then made to understand and simulate the mechanisms by which the defects form during the casting process. The simulations were used to investigate the flow patterns during casting and the growth kinetics of the intermetallic phase. The initial phase of this research established that the defects found comprised of an entrained oxide film entangled with an abundance of intermetallic phase particles. These defects were found to be present in the size range of 0.5 – 5 mm, and were deleterious to the materials mechanical properties. Greater understanding of the ultrasonic inspection process was achieved and informed improvements to assisting the production of high quality feedstock. Simulation of the formation of the defects indicated that there was a region in which the oxide films could form and be free to enter into the final cast product. Simulation of the growth of the intermetallic particles demonstrated that precipitation from the liquid occurs in the mould during which particles are carried by the melt flow and experiences a complex thermal history. The combination of the two phases was established to be due to entanglement of the oxide and particles which when combined will settle out of the melt as a single defect. Improved filtering and melt handling methods were recommended to eliminate the defects and reliably produce high quality alloys.
15
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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16
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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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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18
Li, Dongfa. "Microstructures and mechanical properties of palladium-silver dental casting alloys." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1143105462.
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19
Graziani, Alessandro. "Chemical composition modification of casting aluminium alloys for engine applications." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10018/.
Повний текст джерелаАнотація:
The research activities were focused on evaluating the effect of Mo addition to mechanical properties and microstructure of A354 aluminium casting alloy. Samples, with increasing amount of Mo, were produced and heat treated. After heat treatment and exposition to high temperatures samples underwent microstructural and chemical analyses, hardness and tensile tests. The collected data led to the optimization of both casting parameters, for obtaining a homogeneous Mo distribution in the alloy, and heat treatment parameters, allowing the formation of Mo based strengthening precipitates stable at high temperature.
Microstructural and chemical analyses highlighted how Mo addition in percentage superior to 0.1% wt. can modify the silicon eutectic morphology and hinder the formation of iron based β intermetallics. High temperature exposure curves, instead, showed that after long exposition hardness is slightly influenced by heat treatment while the effect of Mo addition superior to 0,3% is negligible. Tensile tests confirmed that the addition of 0.3%wt Mo induces an increase of about 10% of ultimate tensile strength after high temperature exposition (250°C for 100h) while heat
treatments have slight influence on mechanical behaviour.
These results could be exploited for developing innovative heat treatment sequence able to reduce residual stresses in castings produced with A354 modified with Mo.
20
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.
Повний текст джерелаАнотація:
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.)
21
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.
Повний текст джерелаАнотація:
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.)
22
Wu, Chang Kai. "Predicting the Response of Aluminum Casting Alloys to Heat Treatment." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-dissertations/117.
Повний текст джерелаАнотація:
The objective of this research was to develop and verify a mathematical model and the necessary material database that allow predicting the physical and material property changes that occur in aluminum casting alloys in response to precipitation-hardening heat treatment. The model accounts for all three steps of the typical precipitation hardening heat treatment; i.e., the solutionizing, quenching, and aging steps; and it allows predicting the local hardness and tensile strength, and the local residual stresses, distortion and dimensional changes that develop in the cast component during each step of the heat treatment process. The model uses commercially available finite element software and an extensive database that was developed specifically for the aluminum alloy under consideration - namely A356.2 casting alloy. The database includes the mechanical, physical, and thermal properties of the alloy all as functions of temperature. The model predictions were compared to measurements made on commercial cast components that were heat treated according to standard heat treatment protocols and the model predictions were found to be in good agreement with the measurements.
23
Gelder, Andrew. "Lithium-aluminium casting alloys and their associated metal-mould reactions." Thesis, Aston University, 1992. http://publications.aston.ac.uk/9775/.
Повний текст джерелаАнотація:
Aluminium - lithium alloys are specialist alloys used exclusively by the aerospace industry. They have properties that are favourable to the production of modern military aircraft. The addition of approximately 2.5 percent lithium to aluminium increases the strength characteristics of the new alloys by 10 percent. The same addition has the added advantage of decreasing the density of the resulting alloy by a similar percentage. The disadvantages associated with this alloy are primarily price and castability. The addition of 2.5 weight percent lithium to aluminium results in a price increase of 100% explaining the aerospace exclusivity. The processability of the alloys is restricted to ingot casting and wrought treatment but for complex components precision casting is required. Casting the alloys into sand and investment moulds creates a metal - mould reaction, the consequences of which are intolerable in the production of military hardware. The primary object of this project was to investigate and characterise the reactions occurring between the newly poured metal and surface of the mould and to propose a method of counteracting the metal - mould reaction. The constituents of standard sand and investment moulds were pyrolised with lithium metal in order to simplify the complex in-mould reaction and the products were studied by the solid state techniques of powder X-Ray diffraction and magic angle spinning nuclear magnetic resonance spectroscopy. The results of this study showed that the order of reaction was: Organic reagents> > Silicate reagents> Non silicate reagents Alphaset and Betaset were the two organic binders used to prepare the sand moulds throughout this project. Studies were carried out to characterise these resins in order to determine the factors involved in their reaction with lithium. Analysis revealed that during the curing process the phenolic hydroxide groups are not reacted out and that a redox reaction takes place between these hydroxides and the lithium in the molten alloys. Casting experiments carried out to assess the protection afforded by various hydroxide protecting agents showed that modern effective, protecting chemicals such as bis-trimethyl silyl acetamide and hexamethyldisilazane did not inhibit the metal - mould reaction to a sufficiently high standard and that tri-methylchlorosilane was consistently the best performer. Tri-methyl chlorosilane has a simple functionalizing mechanism compared to other hydroxide protecting reagents and this factor is responsible for its superior inhibiting qualities. Comparative studies of 6Li and 7Li N.M.R. spectra (M.A.S. and `off angle') establish that, for solid state (and even solution) analytical purposes 6Li is the preferred nucleus. 6Li M.A.S.N.M.R. spectra were obtained for thermally treated laponite clay. At temperatures below 800oC both dehydrated and rehydrated samples were considered. The data are consistent with mobility of lithium ions from the trioctahedral clay sites at 600oC. The superior resolution achievable in 6Li M.A.S.N.M.R. is demonstrated in the analysis of a microwave prepared lithium exchanged clay where 6Li spectroscopy revelaed two lithium sites in comparison to 7Li M.A.S.N.M.R. which gave only a single lithium resonance.
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Kotadia, Hirenkumar R. "Solidification behaviour of Al-Sn-Cu immiscible alloys and Al-Si cast alloys processed under intensive shearing." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4517.
Повний текст джерелаАнотація:
Alloy castings are usually solidified with a coarse columnar grain structure under normal casting conditions unless the mode of the solidification is carefully controlled. It is desirable for the grain structure to be fine and equiaxed to improve their mechanical performance as finished castings. It is possible to develop a fine and equiaxed grain structure either by increasing the number of nucleation sites or by grain multiplication. Immiscible alloys with a microstructure in which a soft phase is dispersed homogeneously in a hard matrix have significant potential applications in advanced bearing systems, especially for the automotive industry. Despite considerable efforts made worldwide, including extensive space experiments, no casting techniques so far can produce the desired immiscible microstructure of alloys. Experimental results on Al-Sn-Cu immiscible alloys have confirmed that intensive shearing using melt conditioning by an advanced shearing technology (MCAST) unit, is an effective way to achieve a fine and uniform dispersion of the soft phase without macro-demixing, and that such a dispersed microstructure can be further refined in alloys with precipitation of the primary Al phase prior to the demixing reaction. In addition, it was found that melt shearing at 200 rpm for 60 s will be adequate to produce a fine and uniform dispersion of the Sn phase, and that a higher shearing speed and prolonged shearing time can only achieve further minor refinement. A study of Al-Si hypoeutectic and hypereutectic alloys presents the effects of the processing temperature and intensive shearing on the microstructural and mechanical properties which have been investigated systematically. Attempts have been made to explain the solidification mechanism with intensive melt shearing. The sheared melt was cast into tensile test samples by high pressure die caster (HPDC) to examine the microstructures and mechanical properties. The experimental results reveal that significant grain refinement and uniformity of grains was achieved by the intensive shearing and also a considerable increase in mechanical properties with pouring temperature by changing intermetallic particles morphology, the position of defect band and reduced microscopic defects.
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Krajewski, Katherine Mary. "Corrosion behavior of Ag-Pd dental casting alloys in artificial saliva." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20849.
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Ha, H. U. "Squeeze casting of magnesium-based alloys and their metal matrix composites." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383410.
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Rzyankina, Ekaterina. "Numerical and experimental investigation of directional solidification in vacuum investment casting of superalloys." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1243.
Повний текст джерелаАнотація:
Thesis submitted in fulfilment of the requirements for the degree
Master of Technology: Mechanical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of Technology
2013High temperatures encountered in combustion chambers of jet engines has demanded the creation of new technologies and new materials for the construction of one of the most critical elements of these systems - the stator and rotor turbine blades. They have to withstand extreme temperatures for extended periods without the loss of mechanical strength, conditions under which many steels and alloys fail. Such failure is ascribed to the combination of high temperatures and high centrifugal forces, resulting in creep. The high temperature creep mechanism of grain boundary sliding has limited the operation capability of fine-grained equiaxed castings. Higher operating temperatures were achieved with higher alloy contents and coarse-grained equiaxed castings. This is especially prevalent in multi-crystalline structures in which grain boundaries present weaknesses in the structure. However, notwithstanding these improvements, high temperature resistant alloys formed as single crystal structures offer the necessary material properties for safe performance under these extreme conditions. Damage to turbine blade surfaces is often caused by oxidation and hot corrosion. For this reason, turbine blades are coated with a thermal barrier coating (TBC), which consists of ceramic materials that reduce the heat flux through the airfoil. In this research work, modelling and simulation techniques were initially used to study the directional solidification (DS) of crystal structures during vacuum investment casting. The modelling of the solidification process was implemented using a Finite Element casting simulation software, ProCAST, to predict thermal and flow profiles. These models allowed the study of the dendritic growth rate, the formation of new grains ahead of the solid/liquid interface and the morphology of the dendritic microstructure. These studies indicated the opportunity to optimise the velocity of the solidification front (solidification rate) for single crystal structures. The aim of this research was therefore to investigate the effect of the solidification rate (or withdrawal velocity) on the quality of SC castings. The investigations were carried out for nickel-based superalloy CMSX-4 turbine blade casts and rods using the Bridgman process for vacuum investment casting. The SC castings were heat treated to improve the grain structure for enhanced creep resistance. The heat treated SC castings were inspected by X-ray diffraction to analyse crystallographic orientation and chemical composition; and by SEM, OP (optical microscopy) and microprobe analysis to analyse the microstructure; in addition to macrostructural investigations. In the experimental analysis, the formation of new grains ahead of the solidi/liquid interface and the effect of dendrite packing patterns on the primary dendrite spacing were investigated. Creep tests were conducted to compare the creep properties of the SC castings for different withdrawal rates, and to draw conclusions regarding the effect of withdrawal rate on the microstructure (and hence the creep properties) of SC castings.
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Leyland, Steven Paul. "Casting of single crystal nickel superalloys with reactive elements." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709416.
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Mezger, Peter Richard. "Corrosion behaviour of dental casting alloys some palladium-containing alloy developments : een wetenschappelijke proeve op het gebied van de geneeskunde en tandheelkunde /." Nijmegen : Katholieke Universiteit te Nijmegen, 1989. http://catalog.hathitrust.org/api/volumes/oclc/38087336.html.
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Siavashi, Kiavash. "The effect of casting parameters on the fluidity and porosity of aluminium alloys in the aost foam casting process." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3525/.
Повний текст джерелаАнотація:
The Lost Foam Casting process has been firmly established for Aluminium and ferrous alloys. This process offers many advantages over conventional casting processes but its full potential has yet to be reached due to the many defects introduced to the casting associated with decomposition of the foam pattern during mould filling. The foam pattern commonly used in this process is Expanded Polystyrene (EPS) which degrades to liquid and vapour byproducts. The liquid decomposition byproducts travel to the metal/mould interface, where the globules of liquid foam can become trapped against the coating and their molecular weight is reduced due to the heat from the molten metal. At the same time, they release bubbles of gas into the castings. These globules can wick into the refractory coating only if their molecular weight is sufficiently reduced to below a critical molecular weight. In this study, to improve the quality of Aluminium alloys made by Lost Foam Casting, easier removal of the decomposition byproducts was obtained by using low molecular weight foam patterns. The molecular weight of expanded Polystyrene was not reduced when it was exposed to γ-rays because of cross-linking while the molecular weight of Poly Methyl Methacrylate (PMMA) was significantly due to chain session. Therefore, plates of Probead-70™ (a copolymer of Polystyrene 30 wt %-Poly Methyl Methacrylate 70 wt %) were exposed to γ-rays and reduced their molecular weight by up to about 85% below the critical molecular weight value. With low molecular weight foam patterns the decomposition byproducts require less reduction to reach the critical molecular weight to become absorbed by the coating, and consequently less defects are introduced into the casting. γ-radiation was employed to reduce the molecular weight of the foam. The porosity content of the castings was significantly reduced leading to an improvement of their mechanical properties such as their fatigue life which was increased by 100%. Lost Foam Casting has also been reported to experience complexities with fluidity. Misrun is likely to occur in Lost Foam Casting due to the formation of a large amount of gas at the metal/foam interface, increasing the back pressure, compared to the conventional castings. This reduces the velocity of the molten metal which might lead to solidification of the molten metal before filling the mould entirely. In the current work, a reproducible fluidity test was designed and the effects of different casting parameters on fluidity were examined. In some of the castings inserted thermocouples were employed to study the filling behaviour to determine the velocity of molten metal, thickness of the metal/foam interface and the time of freezing. It was concluded that it is not recommended to alter the coating thickness in order to improve fluidity, because the effect of coating thickness depends on the pouring temperature of the castings and permeability of the coating. The metallostatic pressure was found to affect the fluidity insignificantly (within the values in the current work, 2600-2700 Pa). Instead, increasing coating permeability, decreasing the density of the foam pattern and increasing the pouring temperature were found to increase the fluidity in Lost Foam Casting. However the effect of increasing pouring temperature and decreasing foam density may be detrimental to the quality of castings. The molecular weight of the foam pattern and the use of brominated foam patterns did not have a considerable effect on fluidity in Lost Foam Casting. It was also found that solidification in the Lost Foam Casting occurs at the metal/foam interface. A heat balance between the molten metal and the mould, and the foam pattern, was developed to give a fluidity equation to aid interpretation of the fluidity results. In summary, this research has provided a better understanding of the effect of casting parameters on the fluidity of Lost Foam Casting and the heat transfer from the molten metal to the foam pattern and to the mould. In addition, the quality of AL alloys castings was improved by reducing the molecular weight of the foam pattern used in the Lost Foam Casting process.
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Parmar, Baljit Singh. "The preparation and properties of nanocrystalline soft magnetic materials." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284381.
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Yakoub, M. M. "Squeeze casting of zinc-aluminium (ZA) alloys and ZA-27/SiC composites." Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/25378.
Повний текст джерелаАнотація:
Engineering applications of the recently developed zinc-aluminium casting alloys have been restricted due to certain inherent disadvantages such as segregation. However, segregation can be overcome by thorough mh:!ng of the melt and close temperature control or by rapid solidification of the melt, which can be achieved by squeeze casting. A more serious problem exists in service if components are subjected to a modest temperature increase to about 80°C, when there is a drastic loss of strength. It was therefore thought that the incorporation of ceramic fibres in the matrix could improve the properties of the material at modestly elevated temperatures. In the majority of engineering applications, stresses exist in more than one direction, so castings with isotropic properties are preferred and consequently reinforcement of composite in three dimensions would be necessary to maintain isotropic properties. An investigation was conducted to establish the influence of squeeze casting on the mechanical properties and structure of ZA-8, ZA-12 and ZA-27 alloys. The relationship between these factors and controlled process variables such as die temperature and applied squeeze pressure was established. The mechanical properties of the castings at room temperature and the effect of ageing at 95°C on tensile strength and dimensional changes were established. The results showed a substantial improvement in the tensile strength of the 'as-cast' squeeze cast alloys when compared with the 'as-cast' gravity die cast alloys. In the case of ZA-27 alloy, squeeze casting significantly improved ductility, which is a feature of benefit for all composite systems. The results also showed that pressure and die temperature substantially affect dimensional changes of the alloys when aged at 95°C. A major aspect of the research was the evaluation of the mechanical properties of the fibre reinforced ZA-27 alloy at elevated temperatures. Short silicon carbide fibres were randomly oriented in the matrix to obtain isotropic properties by a technique involving squeeze infiltration, followed by remelting and dispersal in the melt using specially designed equipments. Squeeze casting was used in the final stage of the composite fabrication. Castings of squeeze cast composite (with up to 10% volume fibre) and squeeze infiltrated composite (with up to 18-20% volume fibre) were produced with a sound structure and with fibres that were uniformly distributed and randomly oriented in three dimensions. It was found that the reaction between the fibres and molten alloy must be closely controlled for optimum properties of the composite. In this respect, the optimum time of contact between the fibre and the molten alloy was experimentally determined. It was found that the fibre supplied was of inferior tensile strength, which resulted in poor tensile strength of the tested composite up to a temperature of 100°C. However, the fibre brought substantial Improvement ln the tensile strength of the composite when tested at temperatures of 150 to 250°C. The modulus of elasticity of the composite was substantially improved at room temperature as well as at elevated temperature. The fatigue life of the squeeze cast composite was improved compared with squeeze cast matrix alloy (fibre-free). Squeeze cast composites with 3% volume fibre showed an Improvement in tribological properties compared with squeeze cast matrix alloy and squeeze cast and squeeze infiltrated composites with higher volume percentage of fibre. Wear of cutting tools was adversely affected by the presence of fibre.
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Fourie, Jecois. "Numerical optimisation of the gating system of a titanium alloy inlet valve casting." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/1290.
Повний текст джерелаАнотація:
Dissertation submitted in fulfilment of the requirements for the degree
Master of Technology: Mechanical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of Technology
2014The research described in this dissertation investigates the feasibility of casting inlet valves for an internal combustion engine using Ti6Al4V alloy. The engine valves operate in an extreme environment under high thermal cycles – this requires a material that can withstand such exposures. Ti6Al4V is the most common titanium alloy with high temperature creep and fatigue resistant behaviour, however, it is not all positive. Ti6Al4V alloy also yields many difficulties with respect to processing especially when the material is cast. It is therefore important to gain a thorough understanding of the pouring and solidification characteristics of this material. The main focus of this work was to investigate and optimise feeding and geometrical parameters to produce valves that are free from defects, especially porosity. An in depth analyses of the parameters that influenced the casting quality was performed, and it was found that casting orientation, inlet feeder geometry, initial and boundary conditions all played a vital role in the final results. These parameters were individually investigated by performing detailed numerical simulations using leading simulation software for each of these cases. For each case, a minimum of ten simulations was performed to accurately determine the effect of the alteration on casting soundness and quality. Furthermore, the relationships (if any) were observed and used in subsequent optimised simulations of an entire investment casting tree. The change of geometric orientation and inlet feeder diameter and angle showed distinct relationships with occurrence of porosity. On the other hand, alteration in the pouring parameters, such as temperature and time, had negligible effect on occurrence or position of porosity in the valve. It was found that investigating individual parameters of simple geometry and then utilising these best-fit results in complex geometry yielded beneficial results that would otherwise not be attainable.
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Papazoglou, Efstratios. "On porcelain bonding, oxidation, mechanical properties and high-temperature distortion of high-palladium dental casting alloys." The Ohio State University, 1999. http://catalog.hathitrust.org/api/volumes/oclc/47770015.html.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Ohio State University, 1999.Advisor: William A. Brantley, Oral Biology Program. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
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Begg, John. "Process optimisation in the squeeze casting of zinc-aluminium alloys and composites." Thesis, Loughborough University, 1992. https://dspace.lboro.ac.uk/2134/27495.
Повний текст джерелаАнотація:
Squeeze casting is a process which has the potential to produce castings with exceptional mechanical properties. It also appears to be the most suitable route to produce sound cast metal matrix composites. An investigation was carried out into the squeeze casting of four zinc–aluminium alloys: commercial ZAS (simple eutectic alloy); commercial ZA12 (simple eutectic alloy); commercial ZA27 (peritectic alloy); binary Zn-37Al (solid solution alloy). Although the three commercial alloys can be cast by a variety of conventional gravity and pressure processes it was considered that squeeze casting would produce castings with more homogeneous microstructures and enhanced room temperature properties. The binary Zn-37Al was considered to be a suitable alloy for squeeze casting.
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Elalem, Kaled. "Application of heat pipe technology in permanent mold casting of nonferrous alloys." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85067.
Повний текст джерелаАнотація:
The issue of mold cooling is one, which presents a foundry with a dilemma. On the one hand; the use of air for cooling is safe and practical, however, it is not very effective and high cost. On the other hand, water-cooling can be very effective but it raises serious concerns about safety, especially with a metal such as magnesium. An alternative option that is being developed at McGill University uses heat pipe technology to carry out the cooling.The experimental program consisted of designing a permanent mold to produce AZ91E magnesium alloy and A356 aluminum alloy castings with shrinkage defects. Heat pipes were then used to reduce these defects. The heat pipes used in this work are novel and are patent pending. They are referred to as McGill Heat Pipes.
Computer modeling was used extensively in designing the mold and the heat pipes. Final designs for the mold and the heat pipes were chosen based on the modeling results.
Laboratory tests of the heat pipe were performed before conducting the actual experimental plan. The laboratory testing results verified the excellent performance of the heat pipes as anticipated by the model.
An industrial mold made of H13 tool steel was constructed to cast nonferrous alloys. The heat pipes were installed and initial testing and actual industrial trials were conducted. This is the first time where a McGill heat pipe was used in an industrial permanent mold casting process for nonferrous alloys.
The effects of cooling using heat pipes on AZ91E and A356 were evaluated using computer modeling and experimental trials. Microstructural analyses were conducted to measure the secondary dendrite arm spacing, SDAS, and the grain size to evaluate the cooling effects on the castings. The modeling and the experimental results agreed quite well. The metallurgical differences between AZ91E and A356 were investigated using modeling and experimental results. Selected results from modeling, laboratory and industrial trials are presented. The results show a promising future for heat pipe technology in cooling permanent molds for the casting of nonferrous alloys.
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Barrirero, Jenifer Verfasser], and Frank [Akademischer Betreuer] [Mücklich. "Eutectic modification of Al-Si casting alloys / Jenifer Barrirero ; Betreuer: Frank Mücklich." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2019. http://d-nb.info/1199933139/34.
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Lee, Soon Gi. "Quantitative Characterization of Processing-Microstructure-Properties Relationships in Pressure Die-Cast Mg Alloys." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11552.
Повний текст джерелаАнотація:
The central goal of this research is to quantitatively characterize the relationships between processing, microstructure, and mechanical properties of important high-pressure die-cast (HPDC) Mg-alloys. For this purpose, a new digital image processing technique for automatic detection and segmentation of gas and shrinkage pores in the cast microstructure is developed and it is applied to quantitatively characterize the effects of HPDC process parameters on the size distribution and spatial arrangement of porosity. To get better insights into detailed geometry and distribution of porosity and other microstructural features, an efficient and unbiased montage based serial sectioning technique is applied for reconstruction of three-dimensional microstructures. The quantitative microstructural data have been correlated to the HPDC process parameters and the mechanical properties. The analysis has led to hypothesis of formation of new type of shrinkage porosity called, gas induced shrinkage porosity that has been substantiated via simple heat transfer simulations. The presence of inverse surface macrosegregation has been also shown for the first time in the HPDC Mg-alloys. An image analysis based technique has been proposed for simulations of realistic virtual microstructures that have realistic complex pore morphologies. These virtual microstructures can be implemented in the object oriented finite elements framework to model the variability in the fracture sensitive mechanical properties of the HPDC alloys.
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Symeonidis, Kimon. "The Controlled Diffusion Solidification Process: Fundamentals and Principles." Worcester, Mass. : Worcester Polytechnic Institute, 2009. http://www.wpi.edu/Pubs/ETD/Available/etd-042909-102711/.
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Jiang, Bo. "Solidification behaviour of magnesium alloys." Thesis, Brunel University, 2013. http://bura.brunel.ac.uk/handle/2438/8407.
Повний текст джерелаАнотація:
Magnesium alloys have been extensively used for structural and functional applications due to their low densities. In order to improve the mechanical properties, grain refinement of the microstructures of magnesium alloys has been studied for many years. However, an effective and efficient grain refiner or refinement technique hasn’t been achieved yet, especially for those with aluminium contained. In this study, solution for this problem has been discovered through further understanding of the solidification process, including the potency and the efficiency of nucleation particles, the role of solute, and the role of casting conditions. First of all, the study suggested that MgO particles can act as nuclei in magnesium alloys by measuring and analyzing the differences in cooling curves with various amount of endogenous MgO particles. The differences indicated that the number density of MgO particles has a huge influence on the microstructure. This idea has been fatherly proved by the inoculation of MgO particles in magnesium alloys because the microstructures have been significantly refined after the inoculation. A new kind of refiner (AZ91D-5wt%MgO) has been developed based on such understandings. Secondly, the study discovered that the role of solute has much smaller effect on the grain size than it was suggested in traditional understandings. The inverse-proportional relationship between the grain size and the solute is highly suspected and the major role of solute is to cause columnar- equiaxed transition. The role of casting conditions has also been studied in order to provide experimental evidence for the existence of melt quenching effect in magnesium alloys. It is shown that various casting conditions, such as pouring temperatures and mould temperatures, have large influence on the critical heat balance temperature after rapid pouring. In this study, a theoretical model based on the analysis of cooling curves is presented for grain size prediction. An analytical model of the advance of equiaxed solidification front is developed based on the understanding of the role of casting conditions. Eventually, all these understandings have been applied to magnesium direct-chill (DC) casting. The refined microstructure of DC cast ingots can further assist in understanding the mechanism of advanced shearing achieved by MCAST unit. The comparison of the ingots with and without melt shearing indicated that the advance shearing device can disperse MgO film into individual particles.
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Guthy, Hema Vardhan. "Evolution of the Eutectic Microstructure in Chemically Modified and Unmodified Al-Si Alloys." Digital WPI, 2002. https://digitalcommons.wpi.edu/etd-theses/191.
Повний текст джерелаАнотація:
Aluminum-silicon alloys are an important class of commercial non-ferrous alloys having wide ranging applications in the automotive and aerospace industries. Typical aluminum-silicon alloys have two major microstructural components, namely primary aluminum and an aluminum-silicon eutectic. While nucleation and growth of the primary aluminum in the form of dendrites have been well understood, the understanding of the evolution of the Al-Si eutectic is still incomplete. The microstructural changes caused by the addition of strontium to these alloys is another important phenomenon that still puzzles the scientific community. In this thesis, an effort has been made to understand the evolution of the Al-Si eutectic in the presence and absence of strontium through two sets of experiments: (1) Quench experiments, and (2) sessile drop experiments. The quench experiments were designed to freeze the evolution of the eutectic after various time intervals along the eutectic plateau. The sessile drop experiments were designed to study the role of surface energy in the formation of the eutectic in the presence and absence of strontium. Both experiments were conducted on high purity alloys. Using observations from these experiments, possible mechanis(s) for the evolution of the Al-Si eutectic and the effects of strontium on modifying the eutectic morphology are proposed.
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Rivero, Paz Ive. "The effect of key microstructure features on the machining of an aluminum-silicon casting alloy /." View online, 2010. http://ecommons.txstate.edu/engttad/1.
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Drezet, Jean-Marie. "Direct chill and electromagnetic casting of aluminium alloys: thermomechanical effects and solidification aspects." Lausanne, 2000. http://library.epfl.ch/theses/?display=detail&nr=1509.
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Charbonnier, A. (Alain). "Secondary dendrite ARM spacing determination in Al-Si casting alloys by conductivity measurements." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60694.
Повний текст джерелаАнотація:
Al-Si-Mg alloys containing 7% silicon are the most widely used aluminum foundry alloys owing to their good mechanical properties and excellent castability. Nevertheless, design engineers traditionally apply a design casting factor when designing cast components to ensure that proper strength will be obtained in spite of the recent emergence of techniques of control of the molten alloy quality on which depend, afterwards, the mechanical properties of the castings.In this study, the feasibility of using electrical conductivity to non-destructively predict secondary dendrite arm spacing was investigated on both as-cast and heat treated alloys. In the as-cast condition, conductivity decreases linearly with increasing DAS from 30 $ mu$m, while, below 30 $ mu$m, conductivity readings are influenced by alloying elements retained in solid solution due to the fast solid state cooling rates. Conductivity changes with DAS are more important when the silicon morphology is finer i.e. the alloy modified. After heat treatment, the DAS-conductivity relationships become linear as a result of the homogenisation of the aluminum matrix, but the slopes of the lines are small and the accuracy of DAS determination does not extend below 15 $ mu$m. Conductivity is also greatly influenced by the degree of precipitation achieved during artificial aging so that the determination of DAS by conductivity measurement is best used after quenching (T4 condition).
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Bates, William. "Casting repair and Surface Modification of Aluminum Alloys using Friction Stir Processing (FSP)." Thesis, Högskolan Väst, Avdelningen för Industriell ekonomi, Elektro- och Maskinteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-16675.
Повний текст джерелаАнотація:
This thesis investigates using friction stir welding to repair common surface defects found in aluminum-silicon sand castings. Wherein, the effect of welding parameters: weld RPM, weld speed, and number of weld passes, were evaluated using hardness, porosity density, welding temperature, microstructure refinement as metrics. Therefrom, the results strongly suggest friction stir welding: reduces porosity size, reduces porosity density in a specific area, increases average hardness, improves hardness uniformity, increases surface roughness, redistributes microstructure features in a manner that theoretically improves strength, and maintains a welding temperature less than 660 degrees Celsius.
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Shilvock, W. D. "The effect of alloy and impurity variation on the treatment, casting and physical properties of aluminium-silicon eutectic alloys." Thesis, University of Canterbury. Engineering, 1995. http://hdl.handle.net/10092/8133.
Повний текст джерелаАнотація:
The aluminium-silicon eutectic alloy finds widespread use in commercial light alloy foundries world-wide. The intrinsic characteristics which ensure that this traditional alloy continues in use are excellent fluidity, moderate strength, good ductility, low shrinkage, no requirement for post casting heat treatment and exceptional corrosion resistance. The latter two are particularly noteworthy as they assure the eutectic alloy finds favour in numerous roles for which the higher strength Al-7%Si-Mg alloy is less well suited.
The research reported in this thesis aimed to quantify the changes in physical and structural properties of sand-cast Al-Si eutectic alloy due to compositional variations within the specified range provided by British Standard 1490-LM6. The eutectic alloy was selected for investigation primarily due to members of the local (NZ) aluminium industry expressing concerns regarding consistent production of castings capable of surpassing the physical requirements of the BS1490-LM6 standard.
To achieve the desired aim approximately 500 standard test bars (as used in industry and specified by BS1490) were produced using conditions replicating those encountered in a small, commercial foundry. Each specimen cast was of varying composition with the major variables being Na, Sr, Ti, B, Si, Mg, Mn and Fe. Physical and structural properties including: hardness, tensile strength, ductility, 0.2% proof strength, porosity, grain size and eutectic silicon morphology were monitored for each specimen produced. The combined composition and physical/structural data were then subjected to extensive statistical analysis via multi-linear-regression. The results of the statistical analysis are presented as a series of expressions relating the measured properties to the relevant compositional variables. The sometimes complex and inter-related effects of the elements responsible for significant property variation are illustrated in both numerical and graphical forms.
The full analysis results and associated findings are too numerous to be summarised here. An example of a significant finding is that, with the exception of grain refinement, boron is detrimental to every property monitored. Almost without exception the unwanted effects of boron are already manifest at boron levels as low as 0.01%. Another finding of interest is that within the confines of the given compositional range, the controversial practice of adding manganese to counteract iron-induced embrittlement has little effect on ductility while being highly deleterious to tensile strength. Indeed the embrittling effects of iron were found to be far smaller in magnitude than anticipated given the concern which surrounds this element. This led to the conclusion that further investigation into the effects of iron on parameters such as fatigue endurance warrant investigation.
Two compromises were unavoidable in this research firstly, an inability to assess the level and hence effects of phosphorus variations, and secondly the boron additive used was not of the desired type. Surprisingly, the effects of boron mentioned above were not found to be discernibly influenced by the latter compromise.
Two less significant areas of experimentation were also touched upon in the course of this research, namely the suitability of various materials for use in conditions requiring contact with molten aluminium, and the contamination and compositional variations which occur during degassing by conventional lance and tablet methods.
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Cai, Zhuo. "Metallurgical structures, in vitro corrosion resistance and biocompatibility of high-palladium dental casting alloys." The Ohio State University, 1996. http://catalog.hathitrust.org/api/volumes/oclc/48171767.html.
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Thesis (M.A.)--Ohio State University, 1997.Advisor: William A. Brantley, Dept. of Oral Biology. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
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Zhou, Yipeng. "Solidification behaviour of Fe-rich intermetallic compounds in aluminium alloys." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/15965.
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The industrial use of recycled aluminium is greatly limited by the degraded mechanical properties due to the increased impurities. Fe, one of the common impurity content in Al alloys, is difficult to eliminate once introduced into aluminium during primary production or recycling processes. Due to the low solid solubility of Fe in Al, the formation of Fe-rich intermetallic compounds (Fe-IMCs) is inevitable, which is one of the main causes for the deterioration of mechanical properties in various cast Al alloys. In order to obtain desirable mechanical properties of recycled Al alloys, modification and refinement of the Fe-IMCs are urgently required as the compact and refined morphologies of such intermetallics are generally non detrimental to Al alloy's performance. However, manipulating the solidification behaviour of the Fe-IMCs phases, including nucleation and growth, is very challenging because of the inherently more difficult heterogeneous nucleation of the Fe-IMCs compared with that of a pure metal or a solid solution; and the strong growth anisotropy. Limited understanding on mechanisms of nucleation and growth of the multicomponent Fe-IMCs is available in the literature. The aim of this study is to gain a deeper understanding on the heterogeneous nucleation and growth behaviour of Fe-IMCs in various Al alloys. The nucleation and growth of both primary and eutectic Fe-IMCs have been investigated during various solidification conditions including a number of different cooling rates and casting temperatures. Based on the experimental results of the solidification of several ternary and quaternary alloys, effect of Mg on the solidification behaviour of Fe-IMCs was investigated. Further the surface modified TiB2 particles were used to enhance the heterogeneous nucleation of Fe-IMCs in order to refine the Fe-IMCs particles. The dominant Fe-IMC in Al-5Mg-2Si-1.2Fe-0.7Mn alloy is identified, using transmission electron microscopy (TEM), as α-AlFeMnSi with a body centred cubic (BCC) lattice structure and lattice parameter of 1.256nm. In the current alloy system, the nucleation of primary α-AlFeMnSi occur at lower cooling rate (≤0.8K/s) when required nucleation undercooling is reached, as the slower cooling rate allows longer diffusion time for the solute to form a stable nucleation embryo. When casting with 20K superheat, the size of primary α-AlFeMnSi increases gradually from 24.5±3.1μm (870K/s) to 251.3±75.3μm (0.02K/s) and the size of α-AlFeMnSi eutectic increased gradually from 102.0μm (870K/s) to 623.3μm (0.02K/s). The Fe and Mn concentration in α-AlFeMnSi appears to reduce with the increased cooling rate due to the relatively insufficient solute supply when solute concentration is low (1.2wt.% Fe and 0.7wt.% Mn). Microstructure observation reveals that the {011} plane, especially on <111> orientation, is the preferred growth orientation of BCC primary α-AlFeMnSi, resulting in rhombic dodecahedral in 3D. The eutectic α-AlFeMnSi, prefers to initiate on the primary α-AlFeMnSi. In addition to the substantial nucleation undercooling, the research revealed that the nucleation of primary α-AlFeMnSi also rely on the local solute concentration and the solute diffusion. Compared with α-Al, the growth of α-AlFeMnSi is less sensitive to the cooling rate changes due to the complexities in multi-components interaction and different diffusion efficiency of different elements. The addition of Mg to Al-1.2Fe-0.7Mn and Al-2Si-1.2Fe-0.7Mn alloys was found to lead to a morphology change of Fe-IMCs. Al6(Fe,Mn), the predominant Fe-IMC in the Al-1.2Fe-0.7Mn-xMg alloy, changed from needle morphology to interconnected lamellar morphology when Mg composition increased from 0.004wt.% to 6.04wt%. A Mg-rich layer at about 5-20nm in thickness was commonly observed on the Fe-IMC/α-Al interface in the alloys with Mg content. The eutectic lamellar spacing for Al6(Fe,Mn) increases from 1.8±0.3μm to 4.5±0.8μm when Mg content increased from 0.004wt.% to 6.04wt.%. In the case of α-Al12(Fe,Mn)3Si, the predominant Fe-IMC in Al-2Si-1.2Fe-0.7Mn-yMg alloys, its lamellar spacing of the eutectic increased from 1.4±0.3μm to 3.25±0.8μm when Mg increased from 0.04wt.% to 5.41wt.%. Owing to the strong anisotropy of the Fe-IMC crystals, the segregation of solute Mg on preferred growth orientation is higher, causing greater growth restriction on this orientation. Consequently, the growth velocity on other orientations becomes relatively more significant. To optimise the morphology of Fe-IMCs in Al alloys, a novel Αl-Ti-B(Fe) grain refiner for Fe-IMCs has been developed to enhance the heterogeneous nucleation of Fe-IMCs. The addition of the novel grain refiner to an Al-5Mg-2Si-1.2Fe-0.7Mn alloy under controlled solidification condition results in a considerable refinement of the primary Fe-IMCs from 251.3±75.3μm to 110.9±45.5μm and from 127.3±36.2μm to 76.5±18.2μm at cooling rates of 0.02K/s and 0.15K/s, respectively. TEM investigations on the refiner reveal a Fe-rich adsorption monolayer in a zigzag fashion on the prismatic planes on the boride particles. This surface modification is beneficial for the heterogeneous nucleation of the Fe-IMCs. Further investigation of the Al alloy with this grain refiner addition revealed that there existed specific orientation relationships (ORs) between TiB2 and Fe-IMCs: (001)[020]Al13Fe4 // (11-20)[10-10]TiB2, and (001)[120]Al13Fe4 ∠6.05˚ (11-20)[10-11]TiB2; (0-11)[100]α-AlFeMnSi // (0001)[-2110]TiB2, and (0-11)[111]α-AlFeMnSi ∠4.5˚ (0001)[10-10]TiB2. The Fe adsorption on substrate particle, the observed ORs between TiB2 and Fe-IMCs, and the refinement of primary α-AlFeMnSi with the addition of modified TiB2 provide evidence of structure templating and composition templating required by heterogeneous nucleation of Fe-IMCs. This research has delivered contribution to the understanding and new approach for optimizing the morphology of Fe-IMCs in the Fe-containing Al alloys. Using the slow cooling rates (≤0.15K/s), the formation compact primary α-AlFeMnSi can be considerably encouraged. With a lower casting temperature, the size and volume fraction of large Chinese-script α-AlFeMnSi can be significantly reduced. With addition of reasonable Mg content the morphology of Fe-IMC can be modified. Particularly, with the addition of the Al-Ti-B(Fe) grain refiner in well-controlled condition, the primary α-AlFeMnSi can be significantly refined. Thus, by implementing these approaches, the optimized Fe-IMC morphology in the microstructure of Fe-containing Al alloy is able to offer promising mechanical performance.
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Nemeth, Bill. "Casting conditions and iron variant effects on the subsequent nucleation of Al₂₀Cu₂Mn₃ dispersoid phase in Al-4Cu-0.4Mn-0.2Si alloys." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/20805.
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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.
Повний текст джерелаАнотація:
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.