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Mülazımoğlu, Mehmet Hașim. "Electrical conductivity studies of cast Al-Si and Al-Si-Mg alloys." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75785.
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Cast Al-Si and Al-Si-Mg alloys containing up to 12.6 wt. pct. silicon and 1.0 wt. pct. magnesium were prepared. The changes in electrical conductivity/resistivity of these alloys due to strontium additions have been investigated and explained in terms of variations in microstructure. The conductivity behaviour of strontium-containing and strontium-free alloys was found to exhibit marked differences, depending on the silicon and magnesium contents and the rate of solidification. The electrical conductivity of single phase alloys containing less than 1.60 wt. pct. Si decreased with increasing silicon and magnesium levels. However, strontium had no effect on the conductivity of these solid solution alloys since it does not dissolve appreciably in the aluminum matrix or change the solid solubility of silicon and magnesium in aluminum. Silicon precipitation processes in the supersaturated solid solution alloys of Al-Si and Al-Si-Sr have been examined using the Johnson-Mehl-Avrami equation and found to be isokinetic. Strontium, however, retarded the growth rate of silicon precipitates. Strontium did not affect the kinetics of G.P. zone formation in Al-Si-Mg alloys but it suppressed the formation of stable Mg$ sb2$Si precipitates during subsequent aging at 175$ sp circ$C. Unlike the single phase alloys, two phase Al-Si and Al-Si-Sr alloys, in the range of 2.0 to 12.6 wt. pct. Si, exhibited different electrical conductivity behaviour. The strontium-containing alloys showed a higher conductivity than alloys with no strontium, and this conductivity difference increased as the silicon and magnesium contents were increased and the solidification rate was decreased. It has been demonstrated this difference is due to changes in the silicon morphology. Electron scattering at the interface between the aluminum matrix and the eutectic silicon phase contributes significantly more to the resistivity of unmodified alloys than that of modified alloys. In addition, the resistivity of
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Ho, Catherina R. "Heterogeneous nucleation of Si in Al-Si alloys." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386591.
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McKay, Brian. "Heterogeneous nucleation in Al-Si alloys." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249545.
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Guengoeor, Salih. "Fatigue studies in Al-Mg-Si alloys." Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276359.
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Perez, Emmanuel. "Interdiffusion behavior of U-Mo alloys in contact with Al and Al-Si alloys." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5007.
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U-Mo dispersion and monolithic fuels embedded in Al-alloy matrix are under development to fulfill the requirements of research reactors to use low-enriched molybdenum stabilized uranium alloys as fuels. The system under consideration in this study consisted of body centered cubic gamma] U-Mo alloys embedded in an Al structural matrix. Significant interaction has been observed to take place between the U-Mo fuel and the Al matrix during manufacturing of the fuel-plate system assembly and during irradiation in reactors. These interactions produce Al-rich phases with physical and thermal properties that adversely affect the performance of the fuel system and can lead to premature failure. In this study, interdiffusion and microstructural development in the U-Mo vs. Al system was examined using solid-to-solid diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. pure Al, annealed at 600[degrees]C for 24 hours. The influence of Si alloying addition (up to 5 wt.%) in Al on the interdiffusion microstructural development was also examined using solid-to-solid diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. pure Al, Al-2wt.%Si, and Al-5wt.%Si annealed at 550??C for 1, 5 and 20 hours. To further clarify the diffusional behavior in the U-Mo-Al and U-Mo-Al-Si systems, Al-rich 85.7Al-11.44U-2.86Mo, 87.5Al-10U-2.5Mo, 56.1Al-18.9Si-21.9U-3.1Mo and 69.3Al-11.9Si-18.8U (at.%) alloys were cast and homogenized at 500[degrees]C to determine the equilibrium phases of the system. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA) and X-ray diffraction (XRD) were employed to examine the phase development in the diffusion couples and the cast alloys. In ternary U-Mo-Al diffusion couples annealed at 600[degrees]C for 24 hours, the interdiffusion microstructure consisted of finely dispersed UAl[sub3], UAl[sub4], U[sub6]Mo[sub2]Al[sub20], and UMo[sub2]Al[sub20] phases while the average composition throughout the interdiffusion zone remained constant at approximately 80 at.% Al. The interdiffusion microstructures observed by EPMA, SEM and TEM analyses were correlated to explain the observed morphological development in the interdiffusion zones. The concept of thermodynamic degrees of freedom was used to justify that, although deviations are apparent, the interdiffusion zones did not significantly deviate from an equilibrium condition in order for the observed microstructures to develop. Selected diffusion couples developed periodic bands within the interdiffusion zone as sub-layers in the three-phase regions. Observation of periodic banding was utilized to augment the hypothesis that internal stresses play a significant role in the phase development and evolution of U-Mo vs. pure Al diffusion couples. The addition of Si (up to 5 wt.%) to the Al significantly reduced the growth rate of the interdiffusion zone. The constituent phases and composition within the interdiffusion zone were also modified. When Si was present in the Al terminal alloys, the interdiffusion zones developed layered morphologies with fine distributions of the (U,Mo)(Al,Si)[sub3] and UMo[sub2]Al[sub20] phases. The U[sub6]Mo[sub4]Al[sub43] phase was observed scarcely in Si depleted regions within the interdiffusion zone. The phase development and evolution of the interdiffusion zone was described in terms of thermodynamic degrees of freedom with minimal deviations from equilibrium.ID: 029809410; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 111-115).
Ph.D.
Doctorate
Mechanical, Materials, and Aerospace Engineering
Engineering and Computer Science
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Legait, Pierre-Alexandre. "Formation and distribution of porosity in Al-Si welds." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-050806-132406/.
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Jain, Syadwad. "Corrosion and protection of heterogeneous cast Al-Si (356) and Al-Si-Cu-Fe (380) alloys by chromate and cerium inhibitors." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1145140821.
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Holmestad, Jon. "High-temperature stability of Al-Mg-Si alloys." Thesis, Norwegian University of Science and Technology, Department of Physics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-6347.
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Buha, Joka School of Materials Science & engineering UNSW. "Interrupted ageing of Al-Mg-Si-Cu alloys." Awarded by:University of New South Wales. School of Materials Science and engineering, 2005. http://handle.unsw.edu.au/1959.4/20794.
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This thesis systematically investigates the effects of a recently developed modified ageing procedure of aluminium alloys, termed the T6I6 temper, on the microstructural development and mechanical properties of the Al ??? Mg ??? Si - Cu alloy 6061. For the T6I6 temper, a conventional single stage T6 temper is interrupted by an ageing period at a reduced temperature (65??C) to facilitate secondary precipitation, before resuming the final ageing at the temperature of the initial T6 treatment. The T6I6 temper was found to cause simultaneous increases in tensile properties, hardness, and toughness as compared with 6061 T6. Al ??? Mg ??? Si ??? Cu alloys are medium strength alloys widely used in the automotive industry and their further improvement is underpinned by stringent demands for weight reduction placed on the transportation industry in recent years. The potential for further improvement of the mechanical properties was found in the control of secondary precipitation that may take place even in some fully aged alloys when exposed to reduced temperatures. The overall improvement in the mechanical properties of 6061 T6I6 was attributed to the formation of finer and more densely dispersed precipitates in the final microstructure. The refinement of precipitates was facilitated by control of the precipitation processes and gradual evolution of the microstructure throughout each stage of the T6I6 treatment. The results indicated that the concentration and the chemical environment of the vacancies controlled the precipitation processes in this alloy. Findings also show that the proportion of the different precipitate phases present in the final microstructure, as well as the amount of the solute in these precipitates, can be controlled and modified utilizing secondary precipitation. A number of analytical techniques were used in this study. The evolution of the microstructure was studied using Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Three Dimensional Atom Probe (3DAP). Vacancy-solute interactions were studied using Positron Annihilation Lifetime Spectroscopy (PALS) and 3DAP. The distribution of the solute was studied using 3DAP and Nuclear Magnetic Resonance (NMR). Differential Scanning Calorimetry (DSC) was used to identify precipitation reactions and to determine the stability of vacancy-associated aggregates.
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Emadi, Daryoush. "Porosity formation in Sr-modified Al-Si alloys." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28732.
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Modification of the eutectic silicon in Al-Si foundry alloys by adding strontium is accompanied by an increase of porosity in the casting. This effect on porosity is due to an increase in both the pore size and the pore number density. In an attempt to understand the nature of this problem, the effect of strontium on the probable causes for porosity occurrence due to modification has been investigated.Experimental findings indicate that the addition of strontium to Al-Si alloys increases the volumetric shrinkage due to an increase in solid density, and at the same time reduces the surface tension and increases the viscosity of the liquid. Metallographic observations show that Sr addition slightly decreases the dendrite arm spacing and changes the solid-liquid interface to a more regular shape. Moreover, Sr-modification decreases the eutectic temperature, and therefore, increases the length of the mushy zone while the total solidification time remains constant.
In addition, Sr addition increases the melt inclusion content, but these inclusions do not have a significant effect on pore nucleation. Hydrogen measurement in the liquid shows that Sr-modification has no effect on the rate of melt hydrogen pick-up and does not introduce hydrogen into the melt. Strontium also reduces the hydrogen solubility in the liquid state but has virtually no effect on the solid state solubility.
A solidification model for pore formation has been developed to study the significance of the changes in these parameters on porosity formation. Based on the experimental results and the theoretical analysis, it is concluded that the decrease in the hydrogen solubility in the liquid, the eutectic temperature (or the length of the mushy zone) and the surface tension are the reasons for the observed increase in porosity in modified alloys. Among these parameters, the decrease in the hydrogen solubility in the liquid plays the main role in causing enhanced porosity formation.
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Arvanitis, Aristeidis. "Development of multiphase Mo-Si-Al intermetallic alloys." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/900/.
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Gan, Wei. "Precipitation and strengthening in AL-GE-SI alloys." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1135275701.
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Clode, Michael Paul. "The origin of defects during Al-Mg-Si extrusion." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/8084.
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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.
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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.
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Romero, Diaz Wilmer Ivan. "Development of low density Al-Li-Mg-Si alloys." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8105.
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Verwijs, Johan P. "The modification of silicon in Zn-Al-Si alloys." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ31654.pdf.
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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.
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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.
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Su, Shei Sia. "Development of hypereutectic Al-Si based P/M alloys." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3538/.
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The compaction, sintering and heat treatment processing conditions for the commercial powder, Ecka Alumix 231 with the nominal composition of Al-15Si-2.5Cu-0.5Mg(wt%) have been optimized in this study. It has been found that densification of Ecka Alumix 231 depended largely on the sintering atmosphere and the amount of liquid phase presented. Sintering in nitrogen atmosphere was found to be beneficial due to the formation of AIN which later induced pore filling effect. Presence of hydrogen in the sintering atmosphere, however, was not desirable. Decomposition of MgH2 at higher temperature was suggested to increase the pore pressure and caused detrimental effect on compact densification. The effects of alloy additions (i.e. Cu and/or Ni) on sintering and heat treatment response were also investigated in this study. Addition of copper was found to enhance the sintering response by a significant increase in the sintered density,reduced the peak ageing temperatures and time. Nickel addition, however, was detrimental to both sintering and heat treatment response since it reduced the amount of copper content dissolved in the α-aluminum due to the formation of Al\(_3\)(Ni,Cu)\(_2\) phase. The precipitation sequence for Al-Si-Cu-Mg-(Ni) was suggested to be: Supersaturated solid solution (SSS)→GP zones → θ” → θ’ → θ.
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Lados, Diana Aida. "Fatigue crack growth mechanisms in Al-Si-Mg alloys." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0204104-125758.
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Thesis (Ph. D.)--Worcester Polytechnic Institute.Keywords: Microstructure; Elastic-Plastic Fracture Mechanics; Crack closure; A356; J-integral; Conventionally cast and SSM Al-Si-Mg alloys; Residual stress; Heat treatment; Fatigue crack growth mechanisms; Threshold stress intensity factor; Plastic zone; Paris law; Fracture toughness; Roughness. Includes bibliographical references.
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Maggs, Steven James. "Intermetallic phase selection in dilute Al-Fe-Si alloys." Thesis, University of Leeds, 1996. http://etheses.whiterose.ac.uk/4711/.
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The DC casting of 1000 series AI-Fe-Si alloys often results in the formation of a defect known as the Fir Tree Zone (FI'Z) caused by variations in the type of binary AI-Fe eutectic intennetallic phase. These include AI3Fe, which is the equilibrium phase, and ~Fe, AImFe and AlxFe which are all common metastable phases found in DC cast ingots. Variation in the solidification conditions across a DC cast ingot.in particular, the cooling rate and local solidification velocity, bring about transitions from one intennetallic phase to another. The composition of the alloy, especially the presence of minor trace elements is also known to affect the transitions, but its effect has been less well studied. Equipment was constructed which reliably simulated DC casting conditions and enabled the FfZ to be reproduced. Experiments were conducted to examine the effect of the concentration of Fe, Si (and Fe:Si ratio) and of low levels «0.04 wt %) of Mg, Ti, Ti-B, V and Mn on the occurrence of phases causing the defect. Intennetallic phases extracted from the matrix by dissolution in hot butanol were identified by XRD. It was found that presence of Ti-B grain refmer had a large effect on the intennetallic phase selection, whilst the other trace element additions had lesser effects. In order to understand the way in which each element was affecting phase selection, experiments were conducted using DSC and a Bridgman furnace to isolate the variables of cooling rate and growth velocity respectively. A curve fitting technique was used to obtain values of eutectic nucleation onset temperature from DSC data where the primary aluminium and eutectic peaks overlapped. A technique was developed to extract intennetallic particles from DSC samples for examination in the TEM. It was found that the addition Ti-B grain refmer affected the phase selection by altering the nucleation temperature. The addition of Mg was found to stabilise the equilibrium phase by its affect on both growth temperature an nucleation temperature The effect of Ti was less clear in that it stabilised the equilibrium phase in the DSC experiments but tended to stabilise the metastable phase in the Bridgman experiments.
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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.
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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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Nowak, Magdalena. "Development of niobium boron grain retainer for aluminium silicon alloys." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/8321.
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Aluminium castings with a large grain structure have poor mechanical properties which are primarily due to casting defects as opposed to fine grain structure. The grain refinement practice using chemical addition is well established for wrought alloys, however in the case of casting alloys, the practice of adding grain refiners and the impact on castability is not well established. The addition of well known Al-5Ti-B grain refiner to casting alloys with silicon (Si) content above 3 wt.% is not effective. This is believed to be due to the chemical reaction between Ti and Si. The current research aim is to find an alternative, but effective, chemical phase which can refine Al-Si alloy grains. Based on a crystallographic database search and intermetallic phases found in Aluminium–Niobium-Boron, there exists several iso-structural phases similar to those of Al3Ti and TiB2. We have selected a phase which exhibits chemical phase stability with Si (below 900 oC) and developed a potential novel grain refiner Nb-B for Al-Si cast alloys. Various Al-Si binary alloys and a commercial sourced LM6 (Al-10Si-Mg) cast alloys were cast after novel grain refiner addition to the melt. It is the first time that such fine grain structures were achieved for Al-Si alloys when Si >4wt.%. It is believed that Nb-B grain refiner enhances the heterogeneous nuclei in the melt. The effectiveness of this grain refiner under various cooling rate conditions is investigated to simulate various practical casting conditions. Due to increased heterogeneous nuclei density, a fine grain structure is also obtained at low cooling rates and the grain size is less sensitive to the cooling rate. The processing of high Si containing alloys for complex shaped castings with reduced defects, fine grain structure and improved mechanical properties are now possible.
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Fjellstedt, Carl Jonas. "Crystallisation Processing of Al-base Alloys." Doctoral thesis, KTH, Production Engineering, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3201.
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Thieme, Michael, Frank Bergner, Ingrid Haase, and Hartmut Worch. "Comparative Investigations to Corrosion Fatigue of Al-Cu and Al-Mg-Si Alloys." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-107075.
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One of the serious problems encountered in the use of various materials in technology is the occurrence of fatigue phenomena as an undesirable material damage under cyclic mechanical load. For aluminium alloys this issue is of extremely high importance in case of their utilisation for aircraft purposes, e.g., where a very wide spectrum of frequencies occur. Moreover, the cyclic loading may be joined by the presence of specific electrolyte media. Therefore, the material candidates must be thoroughly examined in view of their sensitivity to fatigue as well as to corrosion fatigue. Usually, the Cu-containing alloy EN-AW 2024 T3 is applied besides 7075 T6 in Airbus aircrafts, but the weldable alloy 6013 T6 is considered to be a potential alternative. Referring to former investigations on the environmental sensitivity (ES) in the fatigue behaviour /1-6/ this paper brings up experimental findings as well as expanded considerations about damaging mechanisms and modelling. The situation with the alloy 6013 T6 is emphasized. The propagation of cracks under cyclic load in different environments, such as vacuum, air or aqueous media, is described by means of fracture mechanics. This enables discrimination in view of the influence of environmental factors and, hence, the participation of corrosion processes.
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Thieme, Michael, Frank Bergner, Ingrid Haase, and Hartmut Worch. "Comparative Investigations to Corrosion Fatigue of Al-Cu and Al-Mg-Si Alloys." Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A26715.
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One of the serious problems encountered in the use of various materials in technology is the occurrence of fatigue phenomena as an undesirable material damage under cyclic mechanical load. For aluminium alloys this issue is of extremely high importance in case of their utilisation for aircraft purposes, e.g., where a very wide spectrum of frequencies occur. Moreover, the cyclic loading may be joined by the presence of specific electrolyte media. Therefore, the material candidates must be thoroughly examined in view of their sensitivity to fatigue as well as to corrosion fatigue. Usually, the Cu-containing alloy EN-AW 2024 T3 is applied besides 7075 T6 in Airbus aircrafts, but the weldable alloy 6013 T6 is considered to be a potential alternative. Referring to former investigations on the environmental sensitivity (ES) in the fatigue behaviour /1-6/ this paper brings up experimental findings as well as expanded considerations about damaging mechanisms and modelling. The situation with the alloy 6013 T6 is emphasized. The propagation of cracks under cyclic load in different environments, such as vacuum, air or aqueous media, is described by means of fracture mechanics. This enables discrimination in view of the influence of environmental factors and, hence, the participation of corrosion processes.
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Kent, Damon. "Age hardening of sintered Al-Cu-Mg-Si-Sn alloys /." St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17893.pdf.
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Xie, Yun. "Development of Al-Mg-Si aluminium alloys for automobile applications." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366371.
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Lambourne, Alexis. "Spray forming of Si-Al alloys for thermal management applications." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:719651c0-9e12-41c7-ae7b-2abaa1320ea1.
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This thesis describes the processing and characterisation of Al-70Si alloys manufactured by gas atomised spray forming at Sandvik-Osprey (Neath, UK) and Oxford University using a newly commissioned spray forming pilot-plant facility. Spray formed Al-70Si (CE7) provides an attractive balance of thermophysical properties making it suitable for thermal management applications. Microstructural characterisation of CE7 was conducted using optical microscopy, image analysis, electron probe micro analysis (EPMA) and electron backscatter diffraction (EBSD). Microscopy revealed an interpenetrating network microstructure consisting of fine, randomly oriented polycrystalline primary Si interpenetrated by large, α-Al grains devoid of eutectic Si. Mechanical testing and thermal cycling simulated a service environment and revealed for the first time crack initiation, growth and blunting mechanisms, the effect of intermetallic phases on the bulk mechanical properties, and anisotropy effects resulting from macrosegregation of Al during solidification. A relationship between the inter-phase interface length and the fracture toughness has been proposed and methods of interface length refinement have been investigated, including chill casting and spray forming. Spray formed CE7 modified with separate additions of B, P, P+Ce and Sr have been microstructurally and mechanically characterised and compared with binary CE7. While alloy additions were effective in refining primary and eutectic Si in chill cast alloys, spray formed alloys showed little change in interface length. Particle injection of Si-Al powder was effective in refining the scale of the spray formed microstructure, and improving mechanical properties. The deleterious effect of intermetallic phases on bulk mechanical properties has been demonstrated and highlighted the importance of melt cleanliness and materials control during manufacturing.
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Dighe, Manish D. "Quantitative characterization of damage evolution in an Al-Si-Mg base cast alloy." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/20219.
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Chan, Chun Yip. "Friction stir processing of aluminium-silicon alloys." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/friction-stir-processing-of-aluminiumsilicon-alloys(0ffc1328-0a9d-4220-ab31-ee52173ed3a1).html.
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Friction Stir Processing (FSP) has the potential for locally enhancing the properties of Al-Si alloy castings, for demanding applications within the automotive industry. In this thesis, the effect of FSP has been examined on three different cast Al-Si alloys:i) A Hypoeutectic Al-8.9wt%Si Alloyii) A Hypereutectic Al-12.1wt%Si Alloyiii) A Hypereutectic Al-12.1wt%Si-2.4wt%Ni AlloyThe influence of different processing parameters has been investigated at a fundamental level. Image analysis of particle size distributions and growth method of tessellation were used to quantify the level of particle refinement and the homogeneity of the second phase spatial distribution. Stop-action experiments were also carried out, to allow the microstructural changes around the tool during FSP to be studied. Two computer models have been explored, in order to predict the temperature distribution and the material flow behaviour. Furthermore, the stability of the microstructure of the friction stir processed material was studied after being heat treated at elevated temperatures. The changes in particle size and grain structure were examined, hardness measurements were taken across the PZ, and tensile testing were carried out at room and elevated temperatures.After FSP, the microstructure of the cast Al-Si alloys was greatly refined. However, differences in microstructure have been observed throughout the PZ, which tended to be better refined and distributed on the advancing side, than the retreating side of the PZ. Changing the processing parameters also influenced the size and spatial distribution of the second phase particles. By studying the changes in microstructure around the tool from the stop-action experiments, and comparing the results to the thermal distribution and material flow behaviour predicted by the computer models, it has been shown that the flow stress, pitch, and temperature of processing, all needed to be considered, when determining the effects that FSP have on the microstructure. FSP caused very little changes to the hardness of the material, while tensile properties were greatly improved, due to the elimination of porosity and refinement of large flawed particles. In terms of the stability of the microstructure after FSP, particle coarsening and abnormal grain growth has been observed during high temperatures heat treatment. Furthermore, the Al2Cu phase was found to dissolve into solid solution at elevated temperatures, so GPZs and solute clustering can then develop within the alloy during natural ageing.
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Jung, Choonho. "Mechanistic selection and growth of twinned bicrystalline primary Si in near eutectic Al-Si alloys." [Ames, Iowa : Iowa State University], 2006.
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Mirzaei, Behzad. "Oxide Hydrogen Interaction and Porosity Development in Al-Si Foundry Alloys." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16352.
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The oxide level of an A356 aluminium alloy will be controlled by (i) melting, casting and remelting A356 aluminium alloy for increasing the bi-films levels in the melt, and by (ii) additions of an extruded aluminium oxide rod directly to the melt. A clean A356 melt (no additions of any particulates) will be used as reference material. The melting experiments will be conducted in an electric resistance furnace under carefully controlled conditions. The three crucible experimental set-up, designed by SINTEF Materials and Chemistry, will be adopted to secure identical conditions for all three melts to be investigated. From each of the melts a series of reproducible castings will be made for tensile test measurements, as well as bend tests. The results from these tests will be statistically analysed. For the assessment of melt quality, in terms of inclusion count and bi-films index, the Porous Disc Filtration Apparatus (PoDFA) and the Reduced Pressure Test (RPT) will be adopted. For the analysis of fracture behaviour Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDX) will be use. The dissolved hydrogen level will be measured by adopting an ALSPEC H probe.If time is given, the data generated in the present work will be compared with results previously obtained by SINTEF Materials and Chemistry for experiments conducted under similar conditions. It is believed that the results from the present study will provide a sound basis for understanding the fundamentals of the key issues involve in the production of high quality aluminium castings.
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Abdollahi, Ahmad. "Effect of Ca as a modifier in hypoeutectic Al-Si alloys." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ43991.pdf.
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Gloria, Ibarra David. "Control of grain refinement of Al-Si alloys by thermal analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0019/NQ55334.pdf.
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Lakshmanan, Anantha Narayanan. "Crystallization and dissolution studies of iron intermetallics in Al-Si alloys." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41666.
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The crystallization behaviour of iron intermetallics during solidification and the dissolution behaviour of iron intermetallics during heat treatment and their subsequent effect on mechanical properties have been studied.Addition of iron decreases DAS and affects eutectic silicon particle size as nucleation and growth of silicon crystals takes place on the $ beta$-AlFeSi platelets, thus minimizing isothermal dendrite arm coarsening at the eutectic temperature. Increase of iron also increases the size and volume percent of the iron bearing intermetallics.
In the absence of manganese, the iron intermetallics crystallize in the $ beta$-phase, at all cooling rates ranging from 0.1 to 20$ sp circ$C/s when cast from a normal casting temperature of 750$ sp circ$C. In the presence of manganese, the iron intermetallic crystallizes in $ alpha$-phase at low cooling rates and in both the $ alpha$- and $ beta$-phases at high cooling rates. This reverse crystallization behaviour is explained based on the segregation effect displayed by the phase diagram.
When the melt is superheated to a high temperature (about 200 to 300 degrees above the liquidus temperature), the iron intermetallic crystallizes in the $ alpha$-phase at high cooling rates. This behaviour is attributed to the fact that $ gamma$-alumina which forms at low melt temperatures ($ le$750$ sp circ$C) acts as a nucleus for crystallization of $ beta$-phase. When the melt is superheated to a high temperature ($ ge$850$ sp circ$C), the $ gamma$-alumina transforms to $ alpha$-alumina. The $ alpha$-alumina is found to be a poor nucleus for the $ beta$-phase crystallization, and as a result the $ alpha$-phase forms. The importance of nucleation and growth undercooling for the crystallization of iron intermetallics is highlighted.
Investigation of the dissolution behaviour of the iron intermetallics on non-equilibrium heat treatment indicates that the $ beta$-phase platelets dissolve slowly through concurrent fragmentation and then dissolution at the plate tips. Addition of manganese hinders the dissolution of iron intermetallics. The amount of liquid phase formed during non-equilibrium heat treatment increases dramatically once a critical temperature is exceeded. This critical temperature is estimated to be 520 and 515$ sp circ$C for samples initially solidified at 10 and 15$ sp circ$C/s respectively.
The 0.15% Fe alloy exhibits the highest tensile strength and percent elongation compared to 1.0% Fe and 1.0% Fe + 0.5% Mn alloys under as-cast and equilibrium heat treated conditions. However, under non-equilibrium heat treatment conditions, ie., 30 degrees above the T4 equilibrium solution temperature, the strength properties of 1.0% Fe alloy exceed, or at least equal, that of the equilibrium heat treated 0.15% Fe alloy.
An attempt is made to correlate the iron intermetallics present in the microstructure and mechanical properties with the associated fracture mode in this alloy.
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MacKay, Robert Ian 1969. "Quantification of iron in Al-Si foundry alloys via thermal analysis." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27238.
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Iron content in aluminum-silicon casting alloys, which contribute to the formation of Al$ sb5$FeSi intermetallic, can be very detrimental to the physical properties of the final cast part.Thermal analysis could provide a cost effective and reliable method to quantify the iron content of the alloy melt before the casting process is performed. The formation of the Al$ sb5$FeSi intermetallic can be resolvable on the cooling curves for aluminum-silicon alloys if the iron content is equal to or greater than 0.6%wt when the cooling rate is 0.10$ sp circ$C/sec. As the iron content gradually increases, the formation temperature of Al$ sb5$FeSi increases and this results in an increase in the duration of the Al$ sb5$FeSi thermal anomaly. A time based parameter associated with the Al$ sb5$FeSi thermal anomaly is also used to quantify the Fe content. Time parameters can be very accurate if the melt volume and heat extraction for the solidifying thermal analysis sample are strictly controlled.
Results of Fe quantification via apparent time parameter of the Al$ sb5$FeSi crystallization for 356,319 and 413 alloys using thermal analysis has been completed for this thesis. (Abstract shortened by UMI.)
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Karimzadeh, F., M. T. Asnaashari, M. H. Enayati, and M. Salehi. "Formation of Nanostructured Al-Mg-Si Alloys and Evaluation Its Properties." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34869.
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In this study, nanostructured Al-Mg-Si (Al6061) alloy was prepared from elemental powders by mechanical alloying and heat treatment. 98.4% aluminum, 1% magnesium, 0.6% silicon powders were mixed
and mechanically alloyed under argon atmosphere. The rotation speed of 500rpm and ball to powder ratio
of 10:1 was employed. The mechanical alloyed powder was isothermally heat treated at 400 degrees Celsius for 2 h under argon atmosphere.
The results showed that after 10h of milling, a solid solution of Al-Mg-Si with a grain size of ~ 40 nm
was produced. The as milled and annealed powder was characterized by scanning electron microscopy
(SEM) and X-ray diffraction (XRD). The microhardness values of alloy increase by increasing MA time.
Mg2Si particles precipitate from solid solution during subsequent annealing. The as milled powder
appeared to have good thermal stability against grain growth so that the grain size after annealing
remained constant (~ 40 nm).
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34869
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Torres, Luis Vanderlei 1983. "Tixoconformação de novas ligas Al-Si-Cu." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264075.
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Orientador: Eugênio José ZoquiTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho tem como objetivo avaliar a tixoconformabilidade de ligas Al-Xwt%Si- 2,5wt%Cu abrangendo todas as etapas do processo: obtenção das ligas tixofundidas, caracterização microestrutural, caracterização do comportamento viscoso e processo de tixoforjamento em dois conjuntos de equipamentos diferentes, a saber, prensa excêntrica e prensa pneumática. As ligas Al-2,0wt%Si-2,5wt%Cu, Al-3,0wt%Si-2,5wt%Cu, Al-4,0wt%Si- 2,5wt%Cu, Al-5,0wt%Si-2,5wt%Cu e Al-7,0wt%Si-2,5wt%Cu foram produzidas via lingotamento estanque com agitação eletromagnética e com técnica de ultra-refino (adição do refinador Al-5,0wt%Ti-1,0wt%B). As ligas foram submetidas a tratamentos térmicos de globularização pelos tempos de 0s, 30s, 90s e 210s, para duas condições de frações sólidas, 45% e 60%; foram realizados ensaios de viscosidade sob as mesmas condições e ensaios de tixoforjamento com a fração sólida de 45% e com todos os tempos de tratamento. Por fim, foram avaliadas as propriedades mecânicas, via ensaios de tração, das peças tixoforjadas. Os tratamentos térmicos promovem a globularização das partículas de fase primária, de forma que os melhores resultados de viscosidade foram alcançados para ligas submetidas às frações sólidas de 45%: todas as ligas apresentaram resultados de viscosidade aparente na faixa de 106 (Pa.s), segundo a literatura, materiais que se encontram nesta faixa de viscosidade possuem o comportamento similar ao do vidro fundido e demonstram alta conformabilidade, mostrando-se viáveis ao processo de tixoconformação. As peças tixoforjadas apresentaram boa conformabilidade preenchendo toda a matriz e reproduzindo sua geometria. Apresentaram boas propriedades mecânicas através dos ensaios de tração e quando submetidas ao tratamento de solubilização apresentaram propriedades mecânicas superiores, ou seja, houve um aumento do limite de escoamento em todas as ligas em torno de 50MPa, aumento no alongamento em torno de 2 a 3 vezes e o aumento do limite de resistência a tração em todas as ligas em torno de 80MPa
Abstract: The goal of this work was to evaluate the thixoformability of Al-Xwt%Si-2,5wt%Cu alloys, including all the stages process: obtaining the thixocasting, characterization in terms of microstructural, characterization of the rheological behavior, and the thixoforging process in two different sets equipment, ie., eccentric press and pneumatic press. The Al-2,0wt%Si-2,5wt%Cu, Al-3,0wt%Si-2,5wt%Cu, Al-4,0wt%Si-2,5wt%Cu, Al-5,0wt%Si-2,5wt%Cu e Al-7,0wt%Si- 2,5wt%Cu alloys were produced by direct casting with electromagnetic stirring and by ultrarefining (addiction of Al-5,0wt%Ti-1,0wt%B). The alloys were submitted to re-heating treatment for 0s, 30s, 90s and 210s in two conditions of solid fraction, 45% and 60%; had been realized tests of viscosity under the same conditions and thixoforging tests with solid fraction of 45% and with all re-heating treatment times. Finally, had been the mechanical properties, by tensile tests, of the thixoforged pieces. Re-heating treatment times promote the solid phase particles globularization, from that the best results of viscosity been reached for alloys treated with solid fractions of 45%: all the alloys presented resulted of apparent viscosity of 106 (Pa.s), literature according to materials that if find in this index of viscosity possess the similar behavior the casting glass and demonstrate high conformability, revealing viable the process thixoforming. The thixoforged piece presented good conformability, total fulfilling of the matrix and reproducing geometry. Showed good mechanical properties by tensile tests and subjected to solubilization treatment had superior mechanical properties, ie, an increase in the yield strength in all alloys about 50MPa, elongation increased approximately 2 to 3 times and increasing the limit of tensile strength in all leagues around 80MPa
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
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Azevedo, Cesar R. de Farias. "Phase diagram and phase transformations in Ti-Al-Si system." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/1278.
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Гусакова, О. В. "Микроструктура быстрозатвердевших фольг сплава Al-28.5 ат. % Ge-1.5 ат. % Si." Thesis, Сумский государственный университет, 2016. http://essuir.sumdu.edu.ua/handle/123456789/45974.
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Повышение прочности паяных конструкций алюминия достигается не только выбором оптимального состава припоя, но и качеством его микроструктуры. В связи с этим актуальна разработка припоев с более низкой по сравнению с силуминами температурой плавления, обеспечивающих комплекс высоких механических и коррозионных свойств паяных соединений.
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Tongsri, Ruangdaj. "Microstructural development during processing of rapidly solidified Al-Fe-(V,Si) alloys." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8607.
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Chen, Chun-Liang. "Characterisation of intermetallic phases in multicomponent Al-Si alloys for piston applications." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/7834.
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Al-Si based casting alloys are widely used for piston applications. This is due to their combination of properties, which include good castability, high strength, light weight, good wear resistance and low thermal expansion. In order for such alloys to meet increasingly demanding operational requirements, such as higher service temperatures and pressures, multicomponent Al-Si alloys, which contain several other alloying additions (Cu, Ni, Mg, Mn and Fe), have been used to further enhance the high temperature strength and fatigue resistance. Improved material properties are strongly dependent upon the morphologies, the thermal and mechanical properties, and the distribution of the intermetallic phases present in these alloys, which are in turn a function of alloy composition and cooling rate. Therefore, the main aim of this work was to characterise the many complex intermetallic phases in multicomponent Al-Si alloys. Five main areas of interest were investigated in this research. Firstly, thermodynamic modelling has been used to predict phase formation in complex alloys, which has been compared with measurements from differential scanning calorimetry (DSC). Secondly, the presence of additional elements in multicomponent Al-Si alloy systems allow many complex intermetallic phases to form, which make microstructural characterisationn on-trivial, as some of the phases have either similar crystal structures or exhibit subtle changes in their chemistries. A combination of electron backscatter diffraction (EBSD) and energy dispersive X-ray analysis (EDX) have therefore been used for discrimination between the various phases. It is shown that this is a powerful technique for microstructure characterisation and provides detailed information which can be related to the microstructuree volution during initial casting and subsequent heat treatment. Additionally, the complex morphologies of intermetallics have also been observed using 3D X-ray tomography. In this present work, a number of different experimental techniques were used to provide a rapid means of phase discrimination in order to validate microstructural evolution models. Thirdly, the mechanical properties of individual intermetallics have been investigated as a function of temperature using high -temperature nanoindentation. In particular, the hardness and modulus of a number of phases have been measured for a range of alloy compositions. The creep behaviour of intermetallic phases was also investigated, since this is important in the determination of the high temperature mechanical properties of alloys. Fourthly, the coefficients of thermal expansion of intermetallic phases were measured by high temperature X-ray diffraction, and thermal expansion anisotropy was also explored to investigate the formation of microcracking. Finally, in order to investigate the effect of both applied mechanical and thermal loads on the formation of cracks, Eshelby modelling has been used to predict the internal stresses of the different intermetallic phases and alloys, with the aid of the experimental data obtained in this work. The phase identity, composition, and the corresponding physical and mechanical properties can be used to inform alloy design strategies which, may facilitate the development of new alloys with improved properties.
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Edwards, Wendy M. "Microstructural and mechanical property modelling for the processing of Al-Si alloys." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/7754.
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The components of a modem internal combustion engine are required to give extreme reliability over extended periods of operation and none is exposed to more arduous conditions than the piston, especially in the pin boss and crown regions of pistons for diesel engines. The increasing emissions requirements and performance targets demanded of direct injection diesel engines has resulted in steep increases in both specific powers and maximum cylinder pressures. This has in turn lead to greater temperatures and pressures being felt by the piston. The adaptation of the piston design to these increasingly demanding load and temperature conditions has required a continuous improvement and innovation in the field of materials and process technologies. The vast majority of the internal combustion engine pistons produced globally are made by a gravity die casting process using Al-Si based alloys. Although Al-Si alloys have been the subject of a great deal of research over the last 30 years, the majority of work has been based on fairly rudimentary characterisation of the microstructures as a function of alloy chemistry and cooling rate. Most of the attention has been paid to the silicon morphology and distribution rather than on a fundamental knowledge of the development of the complex microstructures and intermetallic phases that arise in commercial alloys. However, the properties of cast near-eutectica: luminium-silicon alloys are very strongly influenced by the microstructure, i.e. the primary aluminium, and the interdendritic microconstituents, such as secondary phases, intermetallics, inclusions and porosity. A fine and uniform grain size is often desired as it improves mechanical properties of castings such as tensile strength, ductility and fatigue resistance, and at the same time aids castability, improves porosity distributions and reduces hot tearing susceptibility. A thorough phase characterisation has been carried out using a number of techniques including optical and electron microscopy with electron backscatter diffraction (EBSD), and image analysis. Use was also made of thermodynamic modelling to predict the volume fraction and distribution of phases within the microstructure as a function of chemical composition and process parameters. From this analysis a detailed understanding of the phases occuffing in multicomponent Al-Si alloys was established. Furthermore, additions associated with grain refining, i.e. Ti, Zr and V, have been investigated systematically using commercial and model alloy systems. All three additions were observed to refine the structure of the castings through the formation of the phase A13Ti, although combined additions with Zr were found to be less efficient due to a 'poisoning' effect on the A13Ti. It was also established that there is a strong competition between the effects of grain refiners and P, with the formation of AbTi reducing the nucleating efficiency of AIP to silicon. The nucleation and growth of the primary silicon phase were thus examined by EBSD. AIP was confirmed as nucleating the silicon epitaxially, after which growth continues by surface nucleation, although the presence of twins were seen to influence the shape of the crystal. Finally, suggestions have been made as a consequence of this work for the future development of piston 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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Cupido, Llewellyn Heinrich. "Experimental and numerical investigation of heat treatment of al-si-cu alloy." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/1291.
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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 TechnologyAluminium alloys has seen recent increase usage in the automotive industry. This is due to the global obligation towards carbon emission reduction and fuel efficiency in the transport sector. The good strength-to-weight ratio offered by Al-Si-Cu alloys showed promising results towards the compliance of these environmentally friendly criteria. The enhanced mechanical properties is obtained when the alloy is subjected to the T6 heat treatment process, which cause microstructural changes due to the evolution of intermetallic phases. The process involves solution heat treatment, for dissolving soluble Cu- and Mg-containing phases, the homogenization of alloying elements, and the spheroidisation of eutectic Silicon. It is followed by quenching, for maximum precipitation hardening particle retention in solution, and a further artificial ageing process with the aim to acquire a uniform distribution of small precipitates, for strength improvement. The heat treatment schedule applied in this study was conducted as follows: Solution heat treatment at a temperature of 525°C for 6h Quenching in water of temperature 50°C; Artificial ageing for 8h at a temperature of 175°C, and then after left inside furnace to cool down to room temperature. This is higher than the 520°C, but shorter than the 8-12h, observed in literature. Also, quenching is done at a lower temperature rather than 60°C, and artificial ageing at a higher temperature, rather than the 155°C. This was done to be able to draw a comparison between the MAGMASOFT® simulation, which has this non-adjustable schedule, and the experimental results. The simulated and experimental results were comparable and similar outcomes, but with some discrepancies. Such as the porosity was far more visible and intense in the experimental, than what was predicted by the software. The as-cast and heat treated microstructure revealed the expected evolution of intermetallic particles, such as dissolving of the Al2Cu and the spheroidisation of the eutectic Si phases. Another phase that was identified was the insoluble AlFeSi and other possible Fe-containing phases, which due to the higher solution heat treatment temperature, showed partial fragmentation and dissolution. The study provided practical data about the effect of heat treatment on microstructural evolution and how it affects the properties of the Al-Si-Cu alloy. It also brought to the attention and understanding of how critical pouring temperature is, as it affect the initial nucleation, and cooling rate, and therefore the micro and macro properties.
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Villeneuve, Carl. "Neutralisation et dissolution des intermétalliques de fer dans les alliages Al-Si /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1998. http://theses.uqac.ca.
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Zhu, Baiwei. "On the influence of Si on anodising and mechanical properties of cast aluminium alloys." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-35096.
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The combination of two cost-effective processes, i.e. casting and anodising, would be an interest for the aluminium component applications. However, there are some obstacles in the application of anodising on cast Al alloys. The challenges mostly relate to the alloying elements especially Si and the surface quality. With the development of casting process, cast aluminium alloys with low Si content can be casted, and a complex geometry component with reasonably good surface finish can be achieved. This study aims to identify the influence of Si on anodising and mechanical properties of Al-Si alloys. In this study, six Al-Si alloys with three different Si level and two different Sr level were investigated. Sr acts as a modifier to change the morphology of Si particles. The directional solidification technology was used to vary the microstructure coarseness by controlling the cooling rate to study the influence of Si level, Si particle morphology and cooling rate on mechanical properties, oxide layer formation and corrosion protection performance in cast Al-Si alloys. This study has observed that Si has a significant influence on anodising. During anodising, Si particles are anodised at a lower rate than the Al phase. The presence of Si particles in eutectic phase make the oxide layer locally thinner and more defected due to the low oxide growth rate in eutectic phase. This study observed the presence of residual metallic Al phase beneath or between Si particles. Due to their presence and their geometry, Al can be shielded by Si particles and prevented from oxidation. Si particles also act as a key role in the corrosion protection of oxide layer in Al-Si alloys. The corrosion attack propagates along Si particles as well as oxide defects to the Al substrate. It is found that the morphology of Si particles has a significant influence on the oxide layer formation and corrosion protection performance of the oxide layer on cast Al-Si alloys. A substantially improvement the corrosion resistance of anodised layer on Al-Si alloys is attributed to the morphology change from interconnected flakes to disconnected Si fibres when Sr is added, with less oxide defects and better oxide distribution. The Si level governs the mechanical properties of Al-Si based alloys. An increase of Si content in Al alloys improves the mechanical properties such as ultimate tensile and yield strength as well as hardness of the materials, but decreases the ductility. However, an increase of Si level in Al alloys decreases the thickness of oxide layer, and thereby, the corrosion protection of the oxide layer is deteriorated.Kombinationen av två kostnadseffektiva processer, gjutning och anodisering, är av intresse för tillämpning på aluminiumkomponenter. Det finns dock hinder för tillämpning av anodisering på gjutna aluminiumlegeringar. Utmaningarna relaterar till effekten av legeringselement, i synnerhet Si, och komponentens ytkvalité. Med utvecklingen av gjutprocesser kan aluminiumlegeringar med lågt Si-innehåll gjutas, och komponenter med komplex geometri med förbättrad ytkvalité kan uppnås. Denna studie syftar till att identifiera påverkan av Si på anodisering och mekaniska egenskaper hos Al-Si-baserade legeringar. I denna studie undersöktes sex Al-Si-legeringar med tre nivåer av Si och två nivåer av Sr. Tillsatser av Sr leder till modifikation av morfologin hos Si-partiklar. Med hjälp av tekniken ”riktad stelning” varierades stelningshastigheten för att studera sambanden mellan halten och morfologin av Si, mikrostrukturens grovlek och dess inverkan på mekaniska egenskaper, samt oxidskiktets bildning och korrosionsbeständighet hos gjutna Al-Si-legeringar. Denna studie visar att Si har ett betydande inflytande på anodisering r. Under anodisering, anodiseras Si-partiklar i en lägre takt än Al-fasen. Närvaron av Si-partiklar i eutektisk fas bidrar till ett lokalt förtunnat oxidskikt med fler defekter på grund av den låga oxidtillväxthastigheten i eutektisk fas. Denna studie observerade förekomsten av kvarvarande metalliska Al fasen under eller mellan Si-partiklar. På grund av Si-partiklarnas närvaro och geometri, kan Al skärmas från oxidation. Si-partiklar har även en nyckelroll i korrosionsskydd av oxidskiktet i Al-Si-legeringar. Korrosionsangreppet propagerar längs Si-partiklar samt oxiddefekter till Al-substrat. Morfologin av Si-partiklar har funnits ha en betydande inverkan på oxidskiktets bildning och korrosionsskydd hos gjutna Al-Si-legeringar. En väsentlig förbättring av korrosionsbeständigheten i anodiserat skikt hos Al-Si-legeringar tillskrivs förändring av kiselns morfologi från sammankopplade flingor till osammanhängande fibrer när Sr tillsätts, med mindre oxiddefekter och bättre fördelning av oxid. Si halten påverkar de mekaniska egenskaperna hos Al-Si-baserade legeringar. En ökning av Si innehålleti Al-legeringar förbättrar de mekaniska egenskaperna såsom brott och sträckgräns samt hårdhet hos materialen, men minskar duktiliteten. En ökning med Si halt i Al-legeringar minskar dessvärre tjockleken hos oxidskiktet, och därigenom, försämrar oxidskiktets korrosionsskydd.
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Устинова, Е. В., and Е. В. Суховая. "Структурообразование квазикристаллических сплавов Al-Cu-Fe, легированных Si и B." Thesis, Сумский государственный университет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/39445.
Full textAbstract:
Стабильная икосаэдрическая ψ-фаза (Al[6]Cu[2]Fe), обладающая уникальными свойствами, была обнаружена в системе Al–Cu–Fe. Несмотря на широкое внимание к новому классу квазикристаллов, фазовая диаграмма системы Al–Cu–Fe при легировании Si и B в области существования икосаэдрической фазы не достаточно определена. Влияние легирующих элементов на структуру сплавов Al–Cu–Fe остается спорным. Поэтому целью работы является изучение влияния Si и B на фазовый состав сплавов Al–Cu–Fe.
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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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Zhang, Duyao. "Thermodynamic characterisation of semi-solid processability in alloys based on Al-Si, Al-Cu and Al-Mg binary systems." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/32538.
Full textAbstract:
The processing window is important for the semisolid processability of alloys. Applications of semi-solid metal (SSM) processing, especially aluminium alloys have been expanding for their excellent mechanical properties. However, the alloys well suited and commercially used for SSM processing today are limited in types. The main purpose of this Ph.D. project is to understand what makes an alloy suitable for SSM processing on both aspects of thermodynamics and kinetics. This research started with a fundamental study of binary alloys based on Al-Si, Al-Cu and Al-Mg systems (wt%): Al-1Si, Al-5Si, Al-12Si and Al-17Si; Al-1Cu, Al-2Cu and Al-5Cu; Al-0.5Mg, Al-3Mg and Al-5.5Mg. These are representative of Si, Cu and Mg contents in commercial alloys used for SSM processing. The Single-Pan Scanning Calorimeter (SPSC) and Differential Scanning Calorimeter (DSC) were used to investigate the liquid fraction changes during heating and cooling of these binary alloys. Thermo-Calc and DICTRA (DIffusion-Controlled TRAnsformations) software have been used to predict the fraction liquid versus temperature taking into account both thermodynamics and kinetics. Comparison of the predictions with experimental data revealed that the simulation results show the same pattern with experimental results in the fraction liquid-temperature relationship. However, the SPSC results are closer to the prediction than DSC curves are, even with the relatively large sample size associated with SPSC. This is potentially a significant result as predicting the liquid fraction versus temperature for the heating of a billet for semi-solid processing remains one of the challenges. The results also suggest that the fraction liquid sensitivity to time should be identified as a critical parameter of the process window for semi-solid processing in addition to the fraction liquid sensitivity to temperature. For microstructure investigation, microanalysis techniques, including Scanning Electron Microscopy (SEM) and micro-indentation testing, have been used on polished sections, and compared to theoretical predictions. In addition, some parts of this project are in cooperation with General Research Institute for Nonferrous Metals (GRINM), which aims to design and develop high performance semi-solid alloys. Thermodynamic analysis (both predictions and experiments) were carried out on thixoformed 319s (2.95Cu, 6.10Si, 0.37Mg, wt%) and 201 (4.80Cu, 0.7Ag, wt%) aluminium alloys. SEM techniques and Transmission Electron Microscopy (TEM) were used for the microstructural characterisation. The results showed that the DSC curves were sensitive to microsegregation in SSM alloys and resulted in a lower liquid fraction than the cast alloys calculated through the integration method from the DSC results. Al2Cu phase in SSM alloys 319s and 201 can be dissolved into matrix up to 0.4 % before melting temperature under 3K/min heating rate when compared with 10K/min heating rate. The DSC scan rate should be carefully selected as higher heating rate can inhibit dissolution of the intermetallic phases during heating leading to less accurate liquid fractions predictions.