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Jonker, A., and JH Potgieter. "An evaluation of selected waste resources for utilization in ceramic materials applications." Elsevier, 2004. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000929.
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Many industrial processes generate large amounts of waste. Typical examples include the fertiliser industry (phosphogypsum), ferro-alloy
and steel producers (slag), as well as the power generating industry (fly ash). Although some waste products are currently used to a limited
extend (e.g. fly ash and cement in cement), there is a constant need to find more uses and newapplications for these. This investigation describes
work done to develop a novel ceramic body, which can potentially be used as a ceramic filter for purification of waste water and potable water.
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Albonetti, Rob. "Porosity and intermetallic formation in lost foam casting of 356 alloy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ58012.pdf.
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Du, Pengfei. "Numerical modeling of porosity and macrosegregation in continuous casting of steel." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2482.
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The continuous casting process is a widely used technique in modern steel plants. However, it is a complicated process that is not well understood. The objective of this research is to model the porosity and macrosegregation due to shrinkage related effects and solid deformation in the continuous casting of steel.
Solid phase movements due to bulging and variable roll gap are modeled with a simple algebraic equation based on assumed slab surface deflection. A simplified single domain fluid flow model is derived to predict the pressure field. When liquid pressure drops to zero, porosity starts to form. The distribution of porosity is calculated using the porosity equation which is based on the mass conservation. A macrosegregation model based on the species conservation is derived. With the relative velocity calculated from the pressure results and the solid velocity, macrosegregation is obtained. Since the solid phase velocity is not zero and mixture density is not assumed to be constant, porosity and macrosegregation due to both solid deformation and shrinkage effects are incorporated.
In order to validate the model, the pressure field of a three-dimensional pure metal solidification system is simulated. The results show the feasibility of the proposed model to predict the fluid flow. The porosity and macrosegregation prediction for different casting conditions are performed. The results confirm the necessity of including solid phase deformation in the prediction of porosity and centerline macrosegregation. The results also reveal the relations between different operating conditions (such as degree of bulging, soft reduction, and casting speed) and the porosity/macrosegregation defects in the final product.
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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/.
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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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Binney, Matthew N. "Porosity reduction in high pressure die casting through the use of squeeze pins /." [St. Lucia, Qld.], 2006. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19810.pdf.
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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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Khalajzadeh, Vahid. "Modeling of shrinkage porosity defect formation during alloy solidification." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6155.
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Among all casting defects, shrinkage porosities could significantly reduce the strength of metal parts. As several critical components in aerospace and automotive industries are manufactured through casting processes, ensuring these parts are free of defects and are structurally sound is an important issue. This study investigates the formation of shrinkage-related defects in alloy solidification. To have a better understanding about the defect formation mechanisms, three sets of experimental studies were performed. In the first experiment, a real-time video radiography technique is used for the observation of pore nucleation and growth in a wedge-shaped A356 aluminum casting. An image-processing technique is developed to quantify the amount of through-thickness porosity observed in the real-time radiographic video. Experimental results reveal that the formation of shrinkage porosity in castings has two stages: 1-surface sink formation and 2- internal porosity evolution. The transition from surface sink to internal porosity is defined by a critical coherency limit of . In the second and third experimental sets, two Manganese-Steel (Mn-Steel) castings with different geometries are selected. Several thermocouples are placed at different locations in the sand molds and castings to capture the cooling of different parts during solidification. At the end of solidification, castings are sectioned to observe the porosity distributions on the cut surfaces. To develop alloys’ thermo-physical properties, MAGMAsoft (a casting simulation software package) is used for the thermal simulations. To assure that the thermal simulations are accurate, the properties are adjusted to get a good agreement between simulated and measured temperatures by thermocouples.
Based on the knowledge obtained from the experimental observations, a mathematical model is developed for the prediction of shrinkage porosity in castings. The model, called “advanced feeding model”, includes 3D multi-phase continuity, momentum and pore growth rate equations which inputs the material properties and transient temperature fields, and outputs the feeding velocity, liquid pressure and porosity distributions in castings. To solve the model equations, a computational code with a finite-volume approach is developed for the flow calculations. To validate the model, predicted results are compared with the experimental data. The comparison results show that the advanced feeding model can accurately predict the occurrence of shrinkage porosity defects in metal castings. Finally, the model is optimized by performing several parametric studies on the model variables.
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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.
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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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Raza, Mohsin. "Process development for investment casting of thin-walled components : Manufacturing of light weight components." Licentiate thesis, Mälardalens högskola, Innovation och produktrealisering, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-27807.
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Manufacturing processes are getting more and more complex with increasing demands of advanced and light weight engineering components, especially in aerospace industry. The global requirements on lower fuel consumption and emissions are increasing the demands in lowering weight of cast components. Ability to produce components in lower wall thickness will not only help to reduce the cost of production but also help to improve the efficiency of engineering systems resulting in lower fuel consumption and lesser environmental hazardous emissions. In order to produce thin-walled components, understanding of mechanism behind fluidity as it is effected by casting parameters is very important. Similarly, for complex components study of solidification morphology and its effects on castability is important to understand. The aim of this work was to investigate casting of thin-walled test geometries (less than 2mm) in aero-space grades of alloys. The casting trials were performed to investigate the fluidity as a function of casting parameters and filling system in thin-walled sections. Test geometries with different thickness were cast and evaluated in terms of filled area with respect to casting parameters, ı.e. casting temperature and shell preheat temperature. Different feeding systems were investigated to evaluate effects of filling mode on castability. Similarly for complex components where geometries are very organic in shape, solidification morphology effects the quality of castings. Process parameters, that effect the solidification morphology were identified and evaluated. In order to develop a relation between defect formation and process parameters, solidification behaviour was investigated using simulations and casting trials. Similarly the effect of factors that influence grain structure and flow related defects were studied. It was observed that fluidity is affected by the mode of geometry filling in investment casting process. The filling mode also have different effect on defect formation. A top-gated configuration is strongly affected by casting parameters where as a bottom-gated configuration is more stable and thus fluidity is not significantly affected by variation in casting parameters. Less porosity and flow-related defects were observed in the bottom-gated system as compared to top-gated system. In the study about casting defects as affected by process parameters, it was observed that shell thickness is important to avoid interdendritic shrinkage. It was observed that the increased shell thickness induces a steeper thermal gradient which is essential in order to minimize the width of the mushy zone. It was also observed that a slower cooling rate along with a steeper thermal gradient at the metal-mould interface not only helps to avoid shrinkage porosity but also increases fill-ability in thinner sections. The work presented here is focused on the optimization of process parameters, in order, for instance, to improve castability and reduce the casting defects in investment casting process. The work, however, does not focus on externally influencing the casting conditions or modifying the casting/manufacturing process. The future work towards PhD will be focused on externally improving the casting conditions and investigating other possible route of manufacturing for thin, complex components.
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Heyvaert, Laurent. "Modélisation de la formation des structures et des microporosités durant la solidification d'alliages d'aluminium." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0265/document.
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Cette thèse s’inscrit dans le projet PRINCIPIA (PRocédés INdustriels de Coulée Innovants Pour l'Industrie Aéronautique) de l’ANR MATETPRO (Matériaux et Procédés pour des Produits Performants). L'objectif de ce projet est la promotion de nouveaux alliages aluminium-cuivre-lithium à destination de l'industrie aéronautique afin d'apporter une alternative aux composites. Cependant, ces alliages sont sujet à une importante porosité pour deux raisons : une forte solubilité à l'hydrogène et une facilité d'oxydation. Dans ce projet, le but de la thèse était d'établir un modèle de prédiction de la porosité à l'échelle du produit. La porosité se forme lors de la solidification de l’alliage à cause d'une plus faible solubilité de l'hydrogène dans le solide. La teneur en hydrogène dans la phase liquide va augmenter par ségrégation et provoquer la nucléation des pores. Il est donc nécessaire de prendre en compte la solidification dans la modélisation de la porosité. De plus, la composition locales modifie la cinétique de croissance des pores et la microstructure exerce une contrainte mécanique sur les pores qui modifie leur équilibre chimique. Après une première partie consacrée à améliorer les connaissances sur les phénomène de transport dans la coulée semi-continue d'aluminium, nous avons modélisé la formation de porosité en se basant sur les modèles disponibles. Le modèle a reproduit l'inhomogénéité de la porosité observée expérimentalement sur une plaque d'alliage aluminium-magnésium. L'analyse nous a montré que la limitation de la croissance par le temps de diffusion de l'hydrogène était responsable de ce profil particulier. La densité volumique des pores est critique pour la limitation de la croissance par la diffusion de l’hydrogène. En fonction de la densité, la croissance passe d'une croissance limitée à une croissance non limitéeThis thesis is part of the project PRINCIPIA (PRocédés INdustriels de Coulée Innovants Pour l'Industrie Aéronautique) of the ANR MATEPRO (MATériaux Et PROcédés pour des produits performants). The goal of this project is the promotion of new aluminum-copper-lithium alloys for the aeronautic industry in order to propose an alternative to composite materials. Unfortunately, these alloys are highly sensitive to the appearance of porosity during the alloy creation process. It is due to a high hydrogen solubility and oxidation. Inside this project, my work was to establish a porosity model at the scale of the ingot. Porosity starts to develop during the solidification process due to a lower solubility of hydrogen in the solid phase. Hydrogen content in liquid phase increases by segregation and leads to pores' nucleation. Thus, it is necessary to take into account solidification for porosity-modeling purposes. It is even more important because the alloys' local composition alters the pores' growth and the microstructure modifies the chemical equilibrium by pinching effect.After a first part dedicated to general improvement of knowledge about transport phenomena in DC casting, the porosity formation model was developed based on model found in literature. The model was able to reproduce the inhomogeneity experimentally observed in an aluminum-magnesium ingot. This profile is explained by the hydrogen diffusion time which limits the pore growth. The pore density is critical for the growth limitation by hydrogen diffusion. Depending on the density, the growth switch from a non limited to a limited growth
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Smillie, Matthew John. "Casting and Analysis of Squeeze Cast Aluminium Silicon Eutectic Alloy." Thesis, University of Canterbury. Mechanical Engineering, 2006. http://hdl.handle.net/10092/1086.
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Squeeze casting is the practise of solidifying metals under mechanically applied pressure via a slow displacement of a die volume. It has been shown that squeeze casting enhances the mechanical properties of cast metals. Research into other high integrity casting processes has shown that using techniques that enhance melt quality can further increase the mechanical properties. Therefore a bottom-tapped, bottom-fed squeeze casting machine was designed and built around a pre-existing squeeze casting die designed for uniaxial pressure application. This was used to obtain quantitative metallurgical and microstructural information on the squeeze castings produced, including the effects of common micro-alloying additions of strontium modifier and titanium modifier on the microstructure and hardness of a commercial aluminium silicon eutectic alloy. These were examined using a Taguchi design of experiments approach. It was found that squeeze casting reduced porosity and secondary dendrite arm spacing and increased hardness, and reduced or eliminated increases in porosity and secondary dendrite arm spacing associated with micro-alloying addition. The size of possibly deleterious iron-rich precipitates was reduced, and the morphology of such precipitates changed to a possibly less deleterious form without further alloy additions of manganese. It was also found that melt control and handling is essential for consistent quality of castings in the production of small volume squeeze castings, such as the ones produced in this experimental work.
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Straka, Jakub. "Hodnocení porezity u tlakově litých odlitků z Al slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229463.
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The purpose of this diploma thesis is an evaluation of die-castings porosity, eventually the evaluation of seats with local squeeze in connection with their mechanical and structural properties. The swatches of alloy AISi9Cu3 were taken from the engine block made by Škoda Auto Company, Mladá Boleslav. To the evaluation and the comparison of the results there were used value of porosity with own measure and other student´s thesis of Brno University of technology. Sets of mechanical and structural properties were selected, evaluated and tested by statistical programs.
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Havel, Jiří. "Hodnocení porezity u tlakově litých odlitků z Al slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230266.
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The aim of this diploma thesis is to analyse the porosity of die - cast cast that were made of the alloy AISi9u3 in iron-foundry Skoda Car Mlada Boleslav. The analysis and the sample comparisons are based on my own measurements and are also connected with previous diploma thesis which deals with that issue and was drawn up at Technical University in Brno. All measurements were statistically tested.
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De, Marcos Anthony. "Influence du procédé de coulage-congélation sur la microstructure et les propriétés de matériaux." Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0027/document.
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Au cours de ce travail, l’objectif est d’étudier les liens entre les paramètres du procédé de séchage, la microstructure et les propriétés d’usage du matériau telles que la conductivité thermique et le module d’Young. L’étude a été effectuée sur des matériaux poreux à base d’alumine, oxyde modèle, et à base de bentonite, minéral argileux. Le procédé de séchage utilisé est le procédé de coulage-congélation, qui permet d’obtenir une microstructure orientée et de fabriquer des matériaux anisotropes. L’origine de cette anisotropie provient de la microstructure des échantillons, essentiellement la forme des pores. Les résultats obtenus ont permis de souligner l’importance des paramètres de séchage sur l’anisotropie et les propriétés d’usage du matériau considéré. Par exemple, des valeurs très faibles de la conductivité thermique (0,045 W.m-1.K-1 pour 98 % de porosité) ont été obtenues pour les matériaux à base de bentonite, tout en étant manipulablesThe aim of this thesis is to correlate the shaping process parameters, the microstructure and the material properties, like thermal conductivity and Young modulus. The materials used in this study are alumina and a bentonite, a clay material. The shaping process used is the freeze-casting, which permit to obtain a textural microstructure and anisotropic materials. The origin of this anisotropy is the samples microstructure, in particularly the pores shape. The results highlight the importance of the freeze-casting parameters on the anisotropy and on materials properties. For example, very low values for the thermal conductivity (0,045 W. m-1.K-1 for a porosity of 98 %) are obtained for bentonite material, and they are handleable
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Alat, Ece. "Analysis Of Magnesium Addition, Hydrogen Porosity And T6 Heat Treatment Effecrts On Mechanical And Microstructural Properties Of Pressure Die Cast 7075 Aluminum Alloy." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615018/index.pdf.
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Aluminum alloys are having more attention due to their high specific stiffness and processing advantages. 7075 aluminum alloy is a wrought composition aluminum alloy in the Al-Zn-Mg-Cu series. Due to the significant addition of these alloying
elements, 7075 has higher strength compared to all other aluminum alloys and effective precipitation hardenability characteristic.
On the other hand, aluminum alloys have some drawbacks, which hinder the widespread application of them. One of the most commonly encountered defects in aluminum alloys is the hydrogen porosity. Additionally, in case of 7075, another problem is the lack of fluidity. Magnesium addition is thought to be effective in compensating this deficiency. Accordingly, in this study, die cast 7075 aluminum alloy samples with hydrogen porosity and additional magnesium content were
investigated. The aim was to determine the relationship between hydrogen content and hydrogen porosity, and the effects of hydrogen porosity, additional magnesium
and T6 heat treatment on ultimate tensile and flexural strength properties of pressure die cast 7075 aluminum alloy.
7075 aluminum alloy returns were supplied from a local pressure die casting company. After spectral analysis, pressure die casting was conducted at two stages.
In the first stage, 7075 aluminum alloy with an increase in magnesium concentration was melted and secondly 7075 aluminum alloy was cast directly without any alloying addition. While making those castings, hydrogen content was
measured continuously before each casting operation. As a final operation T6 heat treatment is carried out for certain samples. Finally, in order to accomplish our aim,
mechanical and microstructural examination tests were conducted.
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Míšek, Jakub. "Vliv odplynění na kvalitu odlitků vyrobených technologií vysokotlakého lití." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318844.
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This thesis examines the influence of the degassing process on hydrogen contend and on the quality of part casted by high pressure casting technologies. The type of defects occurring in the casting is analyzed based on macrostructure and microstructure observations. For the overall assessment is used the statistical observation of the evolution trend of scrapping during the experiment. The results show that shortening of the degassing time may affect the incidence of porosity defect.
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Lefner, Jiří. "Hodnocení mechanických a strukturních vlastností nového bloku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228721.
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The purpose of this dilploma thesis is to evaluate mechanical and structural properties of two types casts of Al-alloy (components of the engine block) which were made by different technologies. Die casting with local squeeze casting and without local squeeze casting. First of them is used in lot manufacture of the current engine block. The aim of the foundry is to change the technology and start to produce new block by the die casting without local squeeze casting. The samples were taken from the both parts (lower and upper part) of the current and the new engine block which are made in foundry of Skoda Auto a.c. in Mladá Boleslav. Sets of mechanical and structural properties were selected, evaluated and tested by statistical programs. It was used fifty casts of the engine blocks for the experiment.
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Carvalho, Gustavo Antoniácomi de. "PROCESSAMENTO DE CERÂMICAS COM POROSIDADE GRADUADA UTILIZANDO AS TÉCNICAS DE FREEZE CASTING E COLAGEM DE BARBOTINA." Universidade Estadual de Ponta Grossa, 2018. http://tede2.uepg.br/jspui/handle/prefix/2741.
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Cerâmicas porosas vêm ganhando visibilidade devido a algumas aplicações tecnológicas interessantes, tais como a utilização em eletrólitos sólidos, ânodos de células a combustível, filtros cerâmicos e reposição óssea e dental. Dentre elas, há especial atenção ao estudo de materiais porosos com porosidade graduada, nos quais a quantidade de poros e a morfologia dos mesmos se alteram pelo volume do material. Nesse trabalho foi realizado o processamento e caracterização de materiais cerâmicos de alumina com porosidade graduada a partir das técnicas de freeze casting e colagem de barbotina, utilizando hidróxido de alumínio e amido de arroz como fases de sacrifício. Após a conformação das amostras por esses métodos, a porosidade foi caracterizada por microscopia eletrônica de varredura, pelas medidas de porosidade aparente feita pelo Princípio de Arquimedes e pela distribuição de tamanho de poros feita pela técnica de porosimetria de mercúrio. Foi avaliada também a resistência mecânica das amostras a partir de ensaio de compressão. Foi confirmada a relação entre as amostras processados isoladamente e suas respectivas camadas nas amostras graduadas. Foi observada também uma boa interação interfacial entre cada uma das camadas das amostras graduadas. A porosidade das amostras com porosidade graduada se manteve próxima do esperado, o valor esperado foi determinado a partir da média das amostras processadas isoladamente em relação às camadas do material com porosidade graduada. O ensaio mecânico demonstrou que não houve influência das interfaces dos materiais graduados na sua resistência à compressão.
Porous ceramics have been gaining visibility due to some interesting technological applications, such as its use as solid electrolytes, fuel cell anodes, ceramic filters and bone and dental reposition. Among them, there is special care in studying graded porosity materials, where the quantity of pores and pore morphology changes through the material volume. In this work the processing and characterization of alumina ceramic materials with functionally graded porosity by freeze casting and slip casting techniques using aluminum hydroxide and rice starch as sacrificial template was performed. After conformation, the porosity was characterized through electron scanning microscopy, apparent porosity through Archimedes method and median pore size through mercury porosimetry. The mechanical resistance was also obtained by compression testing. The analysis allowed to confirm the relation between each of the isolated samples’ microstructure and its respective layer in each of the graded materials, also, the graded materials shown good interfacial interaction between each of the layers. The porosity in graded materials kept close to the expected value, which was determined by the medium value of the porosities of the isolated samples respective to the graded material. Mechanical testing shown that there was no influence of the graded material interfaces in its compressive strength.
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Pagano, Eduardo. "OBTENÇÃO DE CERÂMICAS DE ALUMINA COM GRADIENTE FUNCIONAL DE POROSIDADE A PARTIR DE DIFERENTES TÉCNICAS." Universidade Estadual de Ponta Grossa, 2017. http://tede2.uepg.br/jspui/handle/prefix/2414.
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Neste estudo foi realizado a obtenção e caracterização de materiais cerâmicos de alumina com gradiente funcional de porosidade. Foram utilizados como os métodos de processamento a rota de freeze casting em água e a fase de sacrifício utilizando o amido. Os materiais utilizados para a produção das amostras foram a alumina e o amido de milho de pureza analítica. Foram investigadas as características de porosidade quanto a morfologia de poros, distribuição dos poros pela matriz e interferência do processamento na formação destes. Para o estudo da porosidade, os métodos de porosimetria via método de Arquimedes em água e penetração de mercúrio foram aplicados na analise desta porosidade obtida. As propriedades mecânicas, bem como o modo de fratura obtido, também foram investigadas em ensaio de compressão uniaxial em uma máquina de ensaios universal. As imagens obtidas por microscopia eletrônica de varredura auxiliaram a correlacionar os dados obtidos nos ensaios de porosimetrias com a resposta mecânica obtida do material. Os resultados obtidos entre os métodos, quanto à porosidade, revelam diferenças consideráveis na distribuição e quantidade de poros ao se comparar o freeze casting com a fase de sacrifício com amido. Porém quanto a tamanho, os valores se mantiveram bem próximos. A resistência mecânica em compressão é maior nas amostras com amido, porém estas amostras falham de forma catastrófica. As amostras de freeze casting, por sua vez, possuem menor resistência mecânica e tiveram suas fraturas influenciadas por vários fatores durante o processamento. A morfologia de poros e microestrutura apresentada pelos dois métodos aplicados são consequência direta da rota de processamento utilizada. Nas amostras por freeze casting, foram observados canais de poros. Já as amostras com amido como fase de sacrifício, os poros são arredondados e não conectados
In this study, preparation and characterization of alumina ceramic materials with functional porosity gradients were performed. Freeze casting of alumina slurries, using water as the chosen solvent, and sacrificial phase method using corn starch as sacrificial phase, were implemented. The materials used to produce the samples were alumina and analytical purity corn starch. Porosity characteristics were investigated concerning pore morphology, pore distribution in the ceramic matrix and processing route interference in pore formation. The evaluation of porosity was made utilizing porosity determination methods as mercury intrusion and Archimedes method with water as immersion liquid. The mechanical properties, as well as the fracture mode, were investigated during uniaxial compressive test in a universal testing machine. Using the images obtained by scanning electron microscopy (SEM), it was possible to correlate the data obtained in the porosimetry analysis with the mechanical response obtained from the material. In terms of porosity, the results between the processing routes reveal considerable differences in pore distribution and quantity of pores. However, the pore sizes obtained for both methods were pretty close to each other. The mechanical strength during compressive stress was higher in the samples produced via sacrificial phase method, but those samples failed catastrophically. Freeze casting samples, on the other hand, had lower mechanical resistance and their fractures were directly influenced by several factors during their assembly processing. The pore and microstructure morphology presented by both methods were direct consequence of the processing route used. In the samples produced by freeze casting, pore channels were observed. The samples produced via sacrificial phased method using corn starch presented unconnected rounded pores.
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Svoboda, Rostislav. "Tlakově lité odlitky z Mg slitin - trendy vývoje." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228049.
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The aim of this thesis is to determine influence of porosity and shape-factor over mechanical properties, performed on cast samples from Aalen foundry (Germany), that were high pressure die casted from AZ91 D Alloy. Evaluation of these quantities was done using computer software Olympus Five. Measured values were subjected to statistical analysis in order to eliminate gross errors and determine linear dependence between mechanical properties and porosity eventually voids shape factor.
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Jankes, Erik. "Využití řízeného naplyňování slitin Al-Si při tlakovém lití." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231052.
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This master thesis will cover the possibility of using directed gassing of Al-Si alloys in a high pressure die casting foundry. As a control gas, rotary degasser with gaseous 20 % H2 in N2 as a medium was used. Castings were casted via high pressure die casting machine. The aim of this research is to compare internal defect such as porosity or shrinkage of a casts made from degassed and control gassed melt.
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Šolc, Petr. "Využití simulace pro predikci vad a hodnocení odlitků z Al slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228155.
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The aim of this work is comparing three casting process simulation programs for porosity and microstructure prediction capabilities for die-casting. After confronting these results with experimentally measured data taken from real castings it could be said that simulation is pretty accurate for DAS microstructure prediction and hot-spot areas. Amount of measured porosity could not be compared with predicted values because specimens were not taken from the exact hot-spot areas.
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Morávková, Jitka. "Využití simulace pro predikci vad a hodnocení vlastností u tlakově litých odlitků z Al slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229462.
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The purpose of this diploma thesis is comparing the quantity of porosity in die-cast aluminium casting with using simulation. The cast engine blocks were made by high pressure die-casting and a local squeeze casting (LSC) technology. There was also examined the relationship between porosity and mechanical properties of castings. There were evaluated and compared the results of my own measurements with data from previous students theses at the Faculty of Mechanical Engineering BUT. All data were tested by statistical tests. The comparison of simulation results and experimentally measured values was found a good programme-ability to simulate and estimate porosity.
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Blombäck, Oscar, and Marcus Dahlén. "Minimering av porositet vid vakuumassisterad kallkammarpressgjutning av Al-Si : En fallstudie enligt DMAIC på Husqvarna Group." Thesis, Luleå tekniska universitet, Institutionen för ekonomi, teknik, konst och samhälle, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85097.
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Pressgjutna Al-Si komponenter förekommer mer och mer i förbränningsmotorer med syfte att reducera vikt och förbättra hållbarhet. Ett problem vid pressgjutning, en process kännetecknad av kostnadseffektivitet vid massproduktion, är porositetsbildning vilket kan resultera i läckage, strukturell svaghet och försämrad hållbarhet och livslängd för tillverkade komponenter. Då porer oftast bildas internt försvåras dessutom identifiering av potentiellt trasiga komponenter. Det är därför av vikt att finna parameterinställningar i pressgjutningsprocessen vilka konsekvent minimerar porositetsbildning. Ett företag som drabbas av återkommande porositets-relaterade defekter är Husqvarna Group. De använder vakuumassisterad pressgjutning för att, bland annat, producera motorcylindrar av Al-Si. Kassationsgraden, specifikt hänförbar till porositet, för en cylindermodell har under de senaste tre åren fördubblats vilket har resulterat i slöseri av produktionstid och kvalitetsbristkostnader. Vakuumassisterad pressgjutning kan beskrivas stegvis: (1) smält metall hälls i en cylindrisk fyllkammare, (2) en skottkolv trycker smältan mot ett mindre inlopp i låg hastighet för att undvika turbulens, samtidigt som vakuum ansätts i fyllkammare och gjutverktyg, (3) skottkolvshastigheten ökar markant vid en förinställd omslagspunkt, vilket spray-fyller gjutverktyget, och (4) högt tryck ansätts för att eftermata smälta till gjutverktyget när solidifiering sker. Syftet med detta examensarbete har varit att undersöka om och hur diverse parametrar, hänförbara till de nämnda processtegen, påverkar porositetsbildning i en industriell produkt. Därefter applicerades den erhållna processförståelsen för att identifera parametrar kritiska för porositetsbildning och slutligen rekommendera parameterinställningar som konsekvent minimerar porositetsgraden. Det experimentella upplägget bestod av två steg varav det första ämnade undersöka, via simulering, vilka av 6 parametrar som påverkade porositetsgraden utifrån en reducerad tvånivåers försöksdesign. Det andra steget var ett verkligt experiment i produktionsmiljö där de tre identiferade parametrarna från screening-experimentet varierades enligt en central-composite design. Analysen av experimenten resulterade i parameterinställningar som förväntas reducera porositetsgraden med över 70%. En lägre porositetsgrad kommer troligen reducera kassationsgraden av den undersökta cylindermodellen, vilket hade resulterat i finansiell besparing och effektivare produktion. I ett industriellt kontext bidrar detta exjobb huvudsakligen med en systematisk kvalitetsförbättrande metod för pressgjutna komponenter baserad i såväl simulerad som verklig miljö.Pressure die casted Al-Si components are increasingly found inside internal combustion engines, resulting in weight reduction and increased durability. Characteristic to die casting, commonly associated with cost-effective mass production, is the formation of pores which, if unnoticed, can cause leakage, structural deficiencies, and thus reduced durability and life-length of components. Pores commonly appear internally, making identification of faulty components difficult. Therefore, finding parameter settings in the die casting process that consistently minimizes the formation of pores is of importance. A company struggling with porosity-related defects is Husqvarna Group, currently using vacuum-assisted die casting to produce engine cylinders of Al-Si. Scrap-rate, specifically related to porosity, of a particular cylinder model has doubled in the last three years, causing waste of both precious production time and higher quality deficiency costs. A vacuum-assisted die casting process consists of several steps: (1) liquid Al-Si is poured into a cylindrical shot sleeve, (2) a plunger is moved towards a small gate, leading to the die cavity, at low velocity as to not cause turbulence, whilst vacuum is applied throughout the cavity and shot sleeve, (3) plunger velocity is increased substantially at a predetermined switch point, resulting in a spray-filling of the die cavity, and (4) high pressure is applied to continue the feed of molten metal into the cavity as solidification occurs. The purpose of the thesis has been to investigate if and how various parameters, related to the aforementioned four steps of the die casting process, impact the porosity amount in an industrial product. The acquired process knowledge was then applied to identify parameters affecting porosity and recommend settings that consistently minimize the porosity amount. The experimental procedure consisted of two steps: firstly, a screening experiment of six process parameters was made by simulating the die casting process according to a fractional factorial design. Secondly, a real-world experiment was conducted following a central-composite design by varying the three most impactful parameters from the screening experiment. Analysis of the experiments resulted in a selection of parameter settings, anticipated to reduce porosity by over 70%. A lower porosity amount will most likely reduce the scrap rate of the cylinder model, resulting in substantial savings and higher production efficiency. For practitioners, the main contribution of this thesis is a method of systematic quality-improvement to die-casted components by a combination of simulation experiments and real-world tests.
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Palanisamy, Suresh. "Ultrasonic inspection of gas porosity defects in aluminium die castings." Australasian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20060828.103450.
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Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006.A thesis submitted to the Industrial Research Institute Swinburne, Swinburne University of Technology in fulfilment of the requirements to the degree of Doctor of Philosophy, 2006. Typescript. Includes bibliographical references (p. 199-211).
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Viana, Denilson José. "Aplicação do método de Taguchi para redução de porosidade de peças fundidas sob pressão." Universidade de Taubaté, 2012. http://www.bdtd.unitau.br/tedesimplificado/tde_busca/arquivo.php?codArquivo=565.
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O processo de fundição sob pressão de alumínio tem se desenvolvido significativamente nas últimas décadas, ocupando um lugar de destaque na indústria por produzir componentes de engenharia inovadora. Dentre os problemas de qualidade deste processo, o mais recorrente é a porosidade causada por vários fatores, dentre eles os parâmetros do processo que são de difícil determinação, sendo comumente selecionados por meio da abordagem de tentativa e erro. A presente dissertação buscou responder a pergunta: Como determinar a melhor configuração de parâmetros do processo de fundição sob pressão de alumínio para minimizar a porosidade nas peças produzidas? Tendo como objetivo a melhoria da qualidade de uma peça de alumínio, fundida sob pressão, por meio da redução da porosidade. A principal contribuição desta dissertação concentra-se na aplicação do método de Taguchi utilizando dados categóricos ordinais (classes de porosidades) como característica de qualidade, por meio da análise da relação sinal-ruído ponderada. Os resultados dos experimentos foram analisados a partir do efeito médio dos fatores e da análise de variância (ANOVA). Como conclusão os parâmetros de temperatura do metal e velocidade de primeira e segunda fase de injeção foram os mais significativos na redução da porosidade da peça estudada. E ainda, o método de Taguchi alcançou o resultado esperado, trazendo significativa redução de porosidade na peça estudada por meio da otimização dos parâmetros do processo.The aluminum die casting process has developed significantly in recent decades, occupying a prominent place for producing innovative engineering components. Among quality problems of this process is porosity due to several factors, including the process parameters that are difficult to determine, and are commonly selected by trial and error approach. This paper sought to answer the question: How to determine the best set of parameters of the aluminum die casting process to minimize porosity in the parts produced? Aiming improving die casting aluminum parts quality through reducing porosity. The main contribution of this paper focuses on the application of Taguchi method using ordinal categorical data (porosity classes) as a quality characteristic, by analyzing the weighted signal-to-noise ratio. The experimental results were analyzed from the average effect of factors and analysis of variance (ANOVA). In conclusion parameters metal temperature and speed of the first and second injection phase were the most significant in reducing the porosity of the part studied. Also, the Taguchi method achieved the expected result, bringing significant reduction of porosity in the part studied by optimizing the process parameters.
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Klocová, Petra. "Hodnocení porezity u odlitků tlakově litých z Al slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228047.
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The objective of this diploma thesis is an evaluation of die-castings porosity, eventually the evaluation of seats with local squeeze in connection with their mechanical and structural properties. The swatches of alloy AISi9Cu3 were taken from the engine block made by Škoda Auto Company, Mladá Boleslav. To the evaluation and the comparison of the results there were the other VUT FSI Brno students´ theses used.
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Rýdel, David. "Tlakově lité odlitky z Al slitin - trendy vývoje." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228046.
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The objective of this diploma thesis is to state the influence of porosity, DAS and shape factor on mechanical characteristics for the cast transmission cover made in Kovolit Modrice a.s.Which was molten from AlSi9Cu3. It was used an imaging software (Olympus Five) for classification of metallographical structures.
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Yousefian, Pedram. "Pore Formation in Aluminum Castings: Theoretical Calculations and the Extrinsic Effect of Entrained Surface Oxide Films." UNF Digital Commons, 2017. https://digitalcommons.unf.edu/etd/761.
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Aluminum alloy castings are being integrated increasingly into automotive and aerospace assemblies due to their extraordinary properties, especially high strength-to-density ratio. To produce high quality castings, it is necessary to understand the mechanisms of the formation of defects, specifically pores and inclusion, in aluminum. There have been numerous studies on pore formation during solidification which lead to hot tearing and/or reduction in mechanical properties. However, a comprehensive study that correlates pore formation theory with in situ observations and modeling assumptions from the literature as well as experimental observations in not available. The present study is motivated to fill this gap.
An in-depth discussion of pore formation is presented in this study by first reinterpreting in situ observations reported in the literature as well as assumptions commonly made to model pore formation in aluminum castings. The physics of pore formation is reviewed through theoretical fracture pressure calculations based on classical nucleation theory (i) for homogeneous and heterogeneous nucleation, and (ii) with and without dissolved gas, i.e., hydrogen. Based on the fracture pressure for aluminum, critical pore size and corresponding probability of vacancies clustering to form the critical-size pore have been calculated by using thermodynamic data reported in the literature. Calculations show that it is impossible for a pore to nucleate either homogeneously or heterogeneously in aluminum, even with dissolved hydrogen. The formation of pores in aluminum castings can only be explained by inflation of entrained surface oxide films entrained during prior damage to liquid aluminum (bifilms) under reduced pressure and/or with dissolved gas, which involves only growth, avoiding any nucleation problem. This mechanism is consistent with reinterpretations of in situ observations as well as assumptions made in the literature to model pore formation.
To determine whether damage to liquid aluminum by entrainment of surface oxides can be observed and measured, Reduced Pressure Tests (RPT) have been conducted by using high quality, continuously cast A356.0 aluminum alloys ingots. Analyses of RPT samples via micro-computer tomography (μ-CT) scanning have demonstrated that number of pores and volume fraction of pore in aluminum casting increased by raising the pouring height (i.e., velocity of the liquid). Moreover, pore size distributions were observed to be lognormal, consistent with the literature.
Cross-sections of RPT samples have been investigated via scanning electron microscopy. In all cases, the presence of oxygen was detected inside, around and between the pores. The existence of oxide films inside all pores indicates that oxide films act as initiation sites for pores and hydrogen only assist to growth of pores. For the first time, the pore formation is reconciled with physical metallurgy principles, supported by observations of oxide films in aluminum castings. Results clearly indicate that pores are extrinsic defects and can be eliminated by careful design of the entire melting and casting process.
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Singh, Kaushlendra. "Numerical simulation of solidification and porosity formation in castings." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182870813.
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Carpentier, David. "Modélisation de la formation des microporosités lors de la solidification d'alliages à base d'aluminium." Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL125N.
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En fonderie d'aluminium, la présence de microporosités au sein des pièces moulées nuit considérablement à leurs propriétés mécaniques. On comprend par conséquent que la modélisation et la prédiction de la formation des microporosités peuvent être d'un grand soutien pour le fondeur. Dans cette étude, nous avons observé tout d'abord expérimentalement la sensibilité à la formation des microporosités d'alliages binaires d'aluminium-silicium (Al-3%Si, Al-7%Si, Al-11%Si) dans des conditions de solidification unidirectionnelle ou uniforme. La caractérisation de nos essais nous a permis de retrouver certaines tendances déjà observées expérimentalement dans la littérature et notamment une augmentation de la fraction volumique de pores avec: la teneur initiale en hydrogène dissous, une microstructure plus grossière, une pression extérieure plus faible. Au vu de ces résultats, nous avons alors adopté une approche thermodynamique ou nous avons montré notamment que, dans l'intervalle de solidification des alliages d'aluminium, la diminution de la température et l'enrichissement en soluté du liquide résiduel peuvent diminuer considérablement la solubilité de l'hydrogène. Dans ces conditions, la formation des microporosités peut avoir lieu dans les premiers stades de la solidification ou les pertes de pression associées au retrait de solidification sont alors négligeables. Notre étude a abouti à la définition d'un modèle analytique de prédiction de la fraction volumique de pores se caractérisant par les deux étapes suivantes: 1) la détermination de la fraction solide critique à partir de laquelle la formation des microporosités devient thermodynamiquement possible, 2) le calcul de la fraction volumique de pores à partir de la résolution du bilan de masse pour l'hydrogène. Notre approche peut être utilisée pour d'autres alliages d'aluminium et/ou dans des conditions de solidification plus compliquées
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Lee, Peter D. "The formation of hydrogen porosity during the solidification of aluminium alloys." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318700.
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Palanisamy, Suresh, and n/a. "Ultrasonic inspection of gas porosity defects in aluminium die castings." Swinburne University of Technology. Industrial Research Institute Swinburne, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20060828.103450.
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This thesis documents a PhD research program undertaken at Swinburne
University of Technology between the years 2000 and 2004. The research was
funded by the Cooperative Research Centre for Cast Metals Manufacturing and was
undertaken in collaboration with Nissan Casting Plant Australia Pty Ltd and the Ford
Motor Company Australia Limited. This thesis reports on the investigation of the
possibility of using an ultrasonic sensing-based, non-destructive testing system to
detect gas porosity defects in aluminium die casting parts with rough surfaces. The
initial intention was to develop a procedure to obtain ultrasonic signals with the
maximum possible amplitude from defects within the rough surface areas of the
castings. A further intention was to identify defects with the application of a suitable
signal processing technique to the raw ultrasonic signal. The literature review has
indicated that ultrasonic techniques have the potential to be used to detect subsurface
defects in castings. The possibility of classifying very weak ultrasonic signals
obtained from rough surface sections of castings through a neural network approach
was also mentioned in the literature. An extensive search of the literature has
indicated that ultrasonic sensing techniques have not been successfully used to detect
sub-surface defects in aluminium die castings with rough surfaces.
Ultrasonic inspection of castings is difficult due to the influence of
microstructural variations, surface roughness and the complex shape of castings. The
design of the experimental set-up used is also critical in developing a proper
inspection procedure. The experimental set-up of an A-scan ultrasonic inspection rig
used in the research is described in this thesis. Calibration of the apparatus used in
the inspection rig was carried out to ensure the reliability and repeatability of the
results. This thesis describes the procedure used to determine a suitable frequency
range for the inspection of CA313 aluminium alloy castings and detecting porosity
defects while accommodating material variations within the part. The results
obtained from ultrasonic immersion testing indicated that focused probes operating at
frequencies between 5 MHz and 10 MHz are best suited for the inspection of
castings with surface roughness Ra values varying between 50 [micro milli] and 100 [micro milli]. For
the purpose of validating the proposed inspection methodology, gas porosity defects
were simulated through side-drilled holes in the in-gate section of selected sample
castings. Castings with actual porosity defects were also used in this research.
One of the conclusions of this research was that it was extremely difficult to
detect defects in castings with surface roughness above 125 [micro milli]. Once the ultrasonic
signal data was obtained from the sample aluminium die castings with different
surface roughness values ranging from 5 [micro milli] to 150 [micro milli] signal analysis was carried
out. Signal feature extraction was achieved using Fast Fourier Transforms (FFT),
Principal Component Analysis (PCA) and Wavelet Transforms (WT) prior to passing
the ultrasonic signals into a neural network for defect classification. MATLAB tools
were used for neural network and signal pre-processing analysis. The results
indicated that poor classification (less than 75%) was achieved with the WT, PCA
and combination of FFT/PCA and WT/PCA pre-processing techniques for rough
surface signals. However, the classification of the signals pre-processed with the
combination of WT/FFT, FFT/WT and FFT/WT/PCA classifiers provided much
better classification of more than 90% for smooth surface signals and 78% to 84%
for rough surface signals. The results obtained from ultrasonic testing of castings
with both real and simulated defects were validated with X-ray analysis of the
sample castings. The results obtained from this research encourage deeper
investigation of the detection and characterisation of sub-surface defects in castings
at the as-cast stage. Implications for the industrial application of these findings are
discussed and directions for further research presented in this thesis.
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Úředníček, Lukáš. "Rozměrová stabilita odlitků ze slitin Al zhotovených metodou vytavitelného modelu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228150.
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The aim of this paper is to compare a bottom filling of a ceramic form made by lost wax process and a top filling conventional method. A computer simulation of filling and casting solidification will contribute to this comparison. The comparison includes evaluation of readings DAS and characteristic readings of porosity with chosen varieties of casting. The results show that the readings DAS did not change much but characteristic readings of porosity were much better at bottom filling. The computer simulation also showed a certain contribution in the field of model smelting technology.
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Andersson, Linnéa. "Shaping Macroporous Ceramics : templated synthesis, X-ray tomography and permeability." Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-54677.
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Macroporous ceramic materials have found widespread technological application ranging from particulate filters in diesel engines, tissue engineering scaffolds, and as support materials in carbon capture processes. This thesis demonstrates how the pore space of macroporous alumina can be manipulated, analysed in three-dimensions (3D) using visualisation techniques, and functionalised with a CO2-adsorbing material. A novel method was developed to produce macroporous alumina materials: by combining sacrificial templating with thermally expandable polymeric microspheres and gel-casting of an alumina suspension. This method offers a versatile production of macroporous ceramics in which the level of porosity and the pore size distribution can easily be altered by varying the amount and type of spheres. The permeability to fluid flow could be regulated by controlling the connectivity of the pore space and the size of the smallest constrictions between the pores. Sacrificial templating with particle-coated expandable spheres significantly increased the fraction of isolated pore clusters and reduced both the sizes and the numbers of connections between neighbouring pores, compared to templating with un-coated spheres. The macroporous alumina materials were characterised with X-ray micro-computed tomography (μ-CT). The 3D data-sets obtained by X-ray μ-CT were used to calculate the spatial variation in porosity, the throat and pore size distributions and to calculate the permeability to fluid flow. The throat and pore size distributions were also able to be accurately quantified in only one extrusion and intrusion cycle with water-based porosimetry; a relatively novel and simple characterisation technique. The pore walls of the macroporous alumina materials were also coated with zeolite films by a colloidal processing technique. The CO2-uptake of the coated alumina materials and of hierarchically porous monoliths of zeolites was evaluated and compared.As the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: Accepted. Paper 5: Manuscript. Paper 6: Submitted.
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Pallikonda, Mahesh Kumar Pallikonda. "FORMING A METAL MATRIX NANOCOMPOSITE (MMNC) WITH FULLY DISPERSED AND DEAGGLOMERATED MULTIWALLED CARBON NANOTUBES (MWCNTs)." Cleveland State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=csu1503937490966191.
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Julišová, Martina. "Optimalizace tepelného zpracování slitiny hliníku AlSi7Mg0,6." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229932.
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The presented diploma thesis deals with various types of quenching and their respective effects on mechanical and structural properties of AlSi7Mg0.6 alloy castings. Cast with precision casting technology into a self-supporting ceramic shell made by plaster investment technology, flat test bars cast by Alucast were used as experimental samples. Sample castings were used in both cast state and after T6 heat treatment. Air-flow and air-water combination with varying water passage (spraying) were used as the quenching media in the quenching process of the castings. In order to evaluate the effect of five different quenching processes on the structure and mechanical properties of the castings, the method of light microscopy, Brinell hardness test and static traction test were used. Evaluation and porosity and SDAS quantifications were carried out by means of image analysis. Experiments did not prove right the hypothesis holding that low SDAS values inevitably mean higher mechanical properties of the castings. On the other hand, distinct is the negative influence of heterogeneous structure and porosity. Despite the fact that the heat treatment was successful in reducing the influence of structural inhomogeneities, it cannot be concluded that spray quenching has an utterly positive bearing on the mechanical and structural properties of the castings.
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Chintalapati, Pavan. "Solidification under pressure of aluminum castings." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2010r/chintalapati.pdf.
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Thesis (Ph. D)--University of Alabama at Birmingham, 2009.Title from PDF t.p. (viewed June 30, 2010). Additional advisors: Viola L. Acoff, Krishan K. Chawla, Raymond J. Donahue, Gregg M. Janowski, Harry E. Littleton (ad hoc). Includes bibliographical references (p. 143-138).
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Staňková, Markéta. "Hodnocení porezity u odlitků gravitačně litých z Al slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228043.
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Solving of this diploma thesis is evaluation porosity in sequence on mechanical properties from different Al alloys. Castings were made by gravity casting to the iron-mould or gravity casting to the sand. Measurements (mechanical properties, porosity, DAS - dendrite arm spacing, shape factors and sphericity) were statistically analysed and dependencies which were detected were processed to the graphs.
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Meduna, Radek. "Výroba rozlehlých tenkostěnných odlitků z hliníkových slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228297.
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The diploma thesis deals with the production of spacious thin-walled castings of aluminum alloys with a good surface quality. During the casting process, different types of molding sands and aluminum alloys are used. The target of the diploma thesis is to evaluate the casting surface quality, to analyse the defects and to evaluate the results.
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Nováková, Lucie. "Snížení nákladů na výrobu odlitků ze slitin hliníku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228993.
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This thesis deals with solving the most serious internal defects in castings made of aluminum alloys which are cast in sand molds in Slévárna a modelárna Nové Ransko Ltd. The problem solving contains a description of the problematic castings with the investigation of the structure and phases and subsequent detailed analysis of their production. The Author of this thesis also examines the influence of Fe and Mn on a possible formation of the internal porosity with the help of test meltings with the evaluation of the internal structural change. The Author’s design solution is a close checking of chemical composition with regard to the ratio Mn / Fe present in the alloy, the purchase of Foundry Degassing Unit to reduce gassiness of melted metals and better control of gassiness with the help of the appropriate equipment for the density Dichte index.
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Descamps, Michel. "Le Coulage en bande et ses applications. Influence des caractéristiques granulaires des poudres céramiques sur les propriétés des bandes." Valenciennes, 1996. https://ged.uphf.fr/nuxeo/site/esupversions/a11c962c-8384-4282-a070-bba98c0d7a5d.
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L'évolution des propriétés physiques, mécaniques et de surface de matériaux élaborés par coulage en bande (AlN, Al#2O#3) est étudiée en fonction de la concentration de la phase organique utilisée et des caractéristiques poreuses de la bande (volume poreux, diamètre des pores ouverts). Ces propriétés sont régies par les propriétés intrinsèques de la phase organique, le taux de remplissage de la structure poreuse par les composés organiques et le diamètre de la porosité ouverte. Une application originale du coulage en bande est montrée au travers de l'élaboration de cibles d'oxydes multicouches, pour la réalisation de dépôts par pulvérisation cathodique radio-fréquence magnetron. Des cibles constituées de bandes de différents oxydes à pulvériser, (PbO/TiO#2, PbO/TiO#2/ZrO#2), ont permis une obtention rapide de dépôts de titanate de plomb et de titanate zirconate de plomb. La composition chimique désirée est obtenue par l'ajustement des épaisseurs des bandes d'oxydes constitutives des cibles
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Kuo, Claire Taijung. "Customized Porosity in Ceramic Composites via Freeze Casting." Thesis, 2021. https://thesis.library.caltech.edu/14042/3/KuoCT2021_thesis.pdf.
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Freeze casting is a facile pore-forming technique for ceramics as it affords great tunability in pore structure including size, morphology, wall thickness, tortuosity, and alignment. Nevertheless, similar to any other pore-forming techniques, it has limitations in terms of the range of accessible properties. For example, a porous lamellar structure is highly permeable but easily fractures, while the dendritic structure is the opposite. This research seeks to provide strategies used with freeze casting to achieve a combination of properties that go beyond the current limitations and create optimized pore structures with a specific focus on three properties: strength, permeability, and surface area.
Such strategies utilize two composite material principles. First, particle reinforcement was implemented to optimize the mechanical and transport properties. Second, surface area was increased with hierarchical design for enhanced capture or catalysis applications. To optimize the mechanical and transport properties, we reinforced high-permeability lamellar structures with reinforcement fillers of silicon carbide (SiC) whiskers and carbon nanotubes (CNTs). The two fillers afford two different mechanisms of reinforcement: structural and material reinforcement.
Additions of 30 vol.% SiC whiskers increased the compressive strength by 325% at a small expense in permeability. Shear failure, common in lamellar structures, was prevented by the interwall bridges produced via particle engulfment during freezing. These bridges were demonstrated by the change in microstructure, stress-strain behavior, and fracture surfaces. A 2D in-situ solidification experiment was conducted to observe solidification and particle engulfment directly. We proposed a modified engulfment model to account for the complexity stemming from high-aspect ratio particles and non-planar freezing fronts. Reasonable agreement was found between the model, the simulation based on the model, and the experimental values from the freeze-casting and 2D-solidification experiments.
Freeze-casting with CNTs was explored as an alternative reinforcement strategy, but one which maintains the original pore structure. CNTs were pushed aside by the freezing front to pore walls due to their small diameters for low CNT concentration composites (<4.5 wt.%) such that the original pore structures remained. The compressive strength increased, albeit by smaller percentages (118% for 4.3 wt.%) than those with SiC whiskers. The increase was attributed to the toughening of pore walls with no diminishing effect on permeability. In addition, CNTs changed the electrical conductivity by ten orders of magnitude with the addition of 8.2 wt.% of the reinforcement.
Finally, conformal coatings via self-assembly of block copolymers (BCP) were produced by infiltration into a freeze-cast lamellar structure and significantly increased the surface area of the underlying scaffold. A bimodal pore size distribution with nanometer-size pores from the BCP self-assembly and micron-size pores from freeze casting was observed. An increase in compressive strengths was achieved with the introduction of pore hierarchy while retaining permeability of the macroporous structure due to enlarged lamellar spacings from the infiltration process.
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Wang, You-Syuan, and 王佑暄. "Effect of Die Casting Process Conditions on Porosity and Microstructure." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/57274651887740647758.
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碩士國立臺灣海洋大學
機械與機電工程學系
105
In the cold chamber die casting processes, molten metal is forced by a plunger tip to fill mold cavities. Air is often entrapped in the sleeve because of poor flow behavior, resulting in gas porosity and affecting the quality and mechanical properties of castings. The aims of this study is to develop special die casting technology, by virtue of controlling the temperature change of melt in the sleeve and applying squeezing force by plunger movement to master the grain nucleation and growth, to form a specialized structure with high strength inside the casting. The study process is outlined as follows. Molten metal is poured in a shot sleeve for a period of time to cool it reaching the forming temperature. Then, a squeezing force is applied by plunger to form a slurry with special microstructure. Finally, the slurry is forced into the cavities to make the diecasting parts. Experimental parameters including cooling time of molten metal, slow shot velocity, molten metal temperature and filling percentage was investigated by Taguchi method. After the die cast part is cooled to the room temperature, the microstructure and mechanical properties of casting are observed. The proposed method is highly potential to produce castings with special microstructure. The porosity of best experimental condition reduce from 6.16% to 0.79%, nodularity is higher than the conventional die casting about 40.9%. In addition, there is no obvious macro holes appeared in the casting. This can effectively enhance its mechanical properties, especially on toughness.
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Cheng, Ming Cheng, and 鄭明城. "Quantitative Modeling of Porosity Formation in an A356 Aluminum Alloy Cylindrical Casting." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/85521338188288086859.
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碩士國立成功大學
材料科學(工程)學系
84
Producing aluminum alloy castings by low pressure casting has the advantages of semi-automatic production,labor saving, improving casting quality and yieldratio.Hence,low pressure casting is a trend of aluminum castings'''' development.According to Sigworth''''s study , 1/2 to 3/4 of casting rejects are due to theporosity defect. Therefore , the main purpose of this study is to explore thefeeding behave of aluminum low pressure casting. SKD61 permanent mold was used to cast 25φ×150L mm sample.In the experiment, mold temperature, hydrogen content in the melt, and gauge pressure from 0to 1kg/cm^2 were changed to simulate the low pressure casting.Hydrogen contentwas precisely detected by an advanced Alscan hydrogen quantitative analyzer. Moreover , thermal measurements were used to obtain thermal variables in thecasting. The result of the change of mold temperature indicated that increasing moldtemperature can increase the solidification time , eliminate negative thermalgradient and solidus velocity , promote directional solidification , and lower the porosity content in the center of casting. Increasing mold temperature ,however , adversely increased the porosity content in the casting near the feeder by virtue of an increase of solidification time. The result of simulated low pressure casting indicated that, except free end , increasing gauge pressure lowered the solidification time , directionalsolidification in the center of casting,thermal gradient,increased the solidusvelocity, and the cooling rate . The effect of gauge pressure on the porositycontent could be explained by the pressure drop . The pressure drop had a maximum in the center of casting （ >0.58atm ）when using a gauge pressure of 0.5 atm. Therefore,if gauge pressure did not greater than the maximum pressuredrop as mention above , the quality of casting in the center would be poorerthan that of the gravity casting . But the porosity of casting in the centercould be reduced when using 1.0 atm gauge pressure. The pressure drop was small in the feeder and solidification time was much larger than the time ofengaging pressure on the feeder. Therefore , with increasing gauge pressure ,the porosity of casting near the feeder could be reduced . With increasing initial hydrogen content in the melt , the porosity contentof casting could be reduced . A change of initial hydrogen content moved the porosity content level . The porosity content was directly proportional to1/P^★ , and the slope was a function of hydrogen content.
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Chuang, Mei-Hui, and 莊美慧. "Study of reducing Porosity Defect Rate for Die Casting products of Aluminum Alloy." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/9s7v37.
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碩士中原大學
機械工程研究所
104
This research aims to investigate the case for Aluminum alloy A356 with die casting technology of LCD shell’s molding process; because die casting part need to make big investment on mold so RD will make the mold to be used in several versions and the investment can be amortized to a minimum value. Therefore, RD need to keep a thick wall in casting part for prevent different need in CNC machining process in future. Due to the design of thick wall, it would be hard to avoid porosity issues occur in casting part. Especially when porosity is located on CNC machining area, it would be hard to pass IP67 test in the final LCD display. So this research focus in how to use mold flow simulation software to simulate porosity size and porosity location. In order to identify defective symptoms and root causes, we use software C3P.casting to simulate the filling process and analysis potential failures inside the cavity. Then taking advantage of the realistic experiment from the factory we did experiment to prove and validate the efficiency of simulation results. The simulation results would be able to acquire the best filling procedures including gate, runner and material over flow area. This case is mainly focus on LCD display metal cover to do mold flow simulation analysis and reducing the defect rate of porosity. Based on the investigation results of difference between before and after mold modification; before mold modification the porosity size is about 1-2mm and the production yield is low. After mold modification on enlarge the gate size、remove some area of runner and extend over flow length, the mold flow analysis results shows a stable filling procedure within cavity. And we have smaller porosity between 0.1-0.3mm and big improvement on production yield which prove the simulation results.
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Yin, Jen-Tso, and 尹壬佐. "Using Local Squeezing Method to Improve the porosity of High Pressure Die Casting." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/frsgwb.
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碩士國立臺北科技大學
製造科技研究所
106
In high pressure die casting (HPDC), it always occur the defects of Air porosity and Shrinkage Porosity. These two kinds of internal defects will result the poor product strength. In this study, material tensile tests were conducted first, and correct the appropriate interface heat transfer coefficient (IHTC), use the PQ² curve to find the operating pressure and the operating flow rate of this HPDC machine, ProCAST software was used to reduce the gas formation by find the proper pouring height and delay time. By matching the parameters of the piston speed low and high speed velocity and Transfer position, and determine the defect position, and finally uses local squeezing to the defect location. The results show that the squeezing pressure needs to above 213 MPa, the start and end time of the squeezing is between 0.8 - 2.83 sec, and the extrusion depth is 0.5 mm to effectively improve the internal shrinkage defects, it will obtain the optimization product to achieve the non-porosity products.
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Yan, Jin-Fong, and 顏進豐. "Re-evaluation of the Effects of Thermal Parameters on the Casting Porosity of A356 Aluminum Alloy." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/11504393465721587417.
Full textAbstract:
碩士國立臺灣大學
機械工程學系研究所
86
Re-evaluation of the Effects of Thermal Parameters on the Casting Porosity of A356 Aluminum Alloy ABSTRACT The correlations between various thermal parameters and the porosity content in the A356 Al plate castings were re-evaluated in this study. Three different plate thicknesses, namely 0.5", 1.0"and 1.5", together with three different thickness ratios of chill to casting, i.e., 0.5, 1.0, and 1.5, were employed to attain various thermal conditions. In order to achieve a uniform initial melt thermal conditions in the plate castings, three different gating systems were evaluated with the system which concurrently feeds the cavity from three ingates and from the longer side of the castings being determined to be the best design. This gating system ( System C ), which has minimum filling time and temperature loss and most uniform temperature distribution during the filling process, was adopted throughout this research. The chills were shown to increase the solidification cooling rates, the temperature gradients and also the time intervals available for the interdendritic feeding at the final stages of solidification. As a result , the amounts of porosity are reduced at the chill ends of the castings, particularly in the thicker-section castings, such as 1"- and 1.5"-thick plate castings. Among the various thermal parameters evaluated, the "Freezing Index" and the "Feeding Efficiency Factor" have been determined to be the two parameters that exhibit relatively high correlation with the porosity content in the castings. In addition, the correlation coefficients for all thermal parameters evaluated herein are much higher than those reported in the literature. The thermal parameter G^0.38/Vs^1.62 has been found to exhibit good correlation with casting porosity only in castings with a constant thickness, but not with various thickness. This is because the "solidus front velocity, Vs" decreases with increasing casting thickness. The regression equation on percent porosity as a function of solidification cooling rate and temperature gradient has been determined to be: %P=1.41×R^-0.601×G^-0.566 with a relatively high correlation coefficient of R2=0.732. Also, the regression constant for R and G are -0.601 and -0.566, respectively, indicating that these two thermal parameters have rather similar effect on casting porosity. The present results also show that the tensile properties are correlated highly with the extent of casting porosity. Therefore, the thermal parameters that have high correlation with porosity also exhibit good correlation with the tensile properties, such as "Freezing Index" and "Feeding Efficiency Factor".
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Navarro, Aranda Monica. "Comparative study of casting simulation softwares for future use during early stages of product development." Thesis, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-28023.
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Within industrial product development processes there is an increasing demand towards reliable predictions of the material behavior, which aims to promote a property driven development that can reduce the lead times. The implementation of simulation based product development with integrated casting simulation may enable the design engineers to gain an early understanding of the products with relation to castability, and orient the subsequent design refinement so as to achieve the desired mechanical properties. This work investigates the suitability of three commercial casting simulation softwares –MAGMA 5.2, NovaFlow & Solid 4.7.5 (NFS) and Click2Cast 3.0 (C2C)–, with respect to the needs of design engineers, such as prediction of shrinkage porosity and mechanical properties with relation to the design. Simplified solidification simulations suitable for this stage were thus performed for three high pressure die cast components with different geometrical constraints. The comparability between the solidification and cooling behaviour predicted by the three softwares was studied, and showed that a reasonably good agreement between predicted solidification times by MAGMA and NFS could be obtained, albeit not between predictions by MAGMA and C2C. Predictions by the three softwares of the hot spot/porosity areas showed to have a good agreement. The calculation times by each software were compared, and MAGMA was seen to have the best performance, yielding significantly shorter times than NFS and C2C. The results obtained were also compared to experimental investigations of porosity, microstructural coarseness, and mechanical properties. There was a good agreement between the predicted hot spot areas –i.e. areas in the geometry that solidify last– and the findings of porosities in the actual castings, meaning that solidification simulations might be able to provide important information for the prediction of most of shrinkage related porosity locations that are related to the casting geometry. However, the lack of a detailed knowledge at the design stage of the casting process limits the possibilities to predict all porosities. The predicted microstructure and mechanical properties by MAGMA non-ferrous were seen to have a good agreement in trend with the experimental data, albeit the predicted values showed large differences in magnitude with the experimental data. Although, the MAGMA non-ferrous module was not developed for HPDC components, it was interesting to study if it could be applied in this context. However, the models seem to need adoption to the HPDC process and alloys. In conclusion, with a limited knowledge of the manufacturing parameters, simplified solidification simulations may still be able to provide reasonably reliable and useful information during early development stages in order to optimise the design of castings.
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Donchev, Danail [Verfasser]. "Controlling porosity and pore size distribution in green ceramics bodies via Freeze-casting method / von Danail Donchev." 2005. http://d-nb.info/983131392/34.
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