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1
Trejo, Eduardo. "Centrifugal casting of an aluminium alloy". Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3041/.
Testo completoAbstract (sommario):
In centrifugal casting, molten metal is introduced into a mould which is rotated at high speed. The centrifugal force helps to fill thin sections but this benefit may be offset by the effect of the turbulent flow on the casting quality. In this research, the effect of direct and indirect gated mould designs on the quality and reliability of aluminium alloy investment castings made by centrifugal casting was investigated. The scatter in the ultimate bend strength and the modulus of elasticity was analyzed using the Weibull statistical technique, which showed that the Weibull modulus of both properties was significantly improved for the indirect gated cast test bars compared to the direct gated bars. A detailed microstructural characterization was carried out on the cast test bars, which included grain size, dendrite cell size and porosity. Scanning electron microscopy was used to examine and analyze the presence of defects on the fracture surfaces such as shrinkage pores, entrapped bubbles and oxide films resulting from surface turbulence during mould filling. The results indicated a clear correlation between the mechanical properties and the presence of casting defects. Water modelling experiments were carried out using purpose-built experimental centrifugal casting equipment and filling sequences recorded using a high speed video camera. The water modelling results showed that the general tendency for the direct and indirect gated mould designs was that the higher the rotational velocity, the lower the filling length and consequently the lower the filling rate. Subsequently, this information was used to validate the computer software ANSYS CFX. An excellent correlation was obtained between the experimental water modelling and simulation results for both direct and indirect gated moulds.
2
Manson-Whitton, Chris. "Squeeze casting of a conventionally wrought aluminium alloy". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403577.
Testo completo
3
Gradwell, K. I. "Precipitation in a high strength magnesium casting alloy". Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492848.
Testo completo
4
Tantipaibulvut, Chairath. "An evaluation of the production of magnesium base alloy castings by the expendable pattern casting process". Thesis, Loughborough University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250959.
Testo completo
5
Spataro, Mark Paul. "Comparison of mechanical performance between magnesium alloy sand castings and high pressure die castings /". [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18378.pdf.
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6
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.
Testo completoAbstract (sommario):
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.
7
Butler, Simon Andrew. "The development of a reliable high strength aluminium casting alloy". Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.570853.
Testo completoAbstract (sommario):
An investigation was carried out into the variability of tensile properties of A201 aluminium alloy investment castings. Fracture surfaces and microstructures of tensile specimens were examined by scanning electron and light microscopy. Chemical analysis of phases was carried out using energy dispersive x-ray analysis. Casting composition variations were measured using spark emission spectroscopy. The main factors that contributed to the variation of properties were incipient grain boundary melting during heat treatment, the macro segregation of chemical alloying elements and interdendritic porosity that had not sealed during the hot isostatic pressing (HIPping) process. Simple step plate castings were produced to investigate the effect of changes in section thickness on the local segregation of alloying elements. The compositional variations occur due to the flow of solute rich liquid through the dendrite interstices in the mushy zone. An investigation was carried out into the effect of titanium diboride particles on the formation of macro segregation and interdendritic porosity. It was found that by increasing the concentration of titanium diboride particles above 2.7 +/- 0.2 % the tendency for macro segregation was reduced to negligible levels. The formation of surface connected pores, as revealed by dye penetrant examination, was also reduced when this. concentration was exceeded. The change in the solidification behaviour is due to a lack of coherent dendrite formation in the mushy zone. This results in solidification contraction being compensated for by mass feeding rather than interdendritic fluid flow of liquid through the dendrite interstices. An additional effect of the presence of the particles was to prevent the formation of a low melting point'phase containing copper, magnesium and silver. This reduced the susceptibility of the alloy to grain boundary incipient melting during solution heat treatment. In the light of the findings of the experimental work the concept of casting reliability is discussed. The importance of preventing the variability of tensile properties by robust alloy design is highlighted. The future design and development of reliable components with regard to process specification and property prediction is discussed.
8
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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9
Gorsky, Daniel A. "Niyama Based Taper Optimizations in Steel Alloy Castings". Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1316191746.
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10
Mezger, Peter Richard. "Corrosion behaviour of dental casting alloys some palladium-containing alloy developments : een wetenschappelijke proeve op het gebied van de geneeskunde en tandheelkunde /". Nijmegen : Katholieke Universiteit te Nijmegen, 1989. http://catalog.hathitrust.org/api/volumes/oclc/38087336.html.
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11
Parmar, Baljit Singh. "The preparation and properties of nanocrystalline soft magnetic materials". Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284381.
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12
Yakoub, M. M. "Squeeze casting of zinc-aluminium (ZA) alloys and ZA-27/SiC composites". Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/25378.
Testo completoAbstract (sommario):
Engineering applications of the recently developed zinc-aluminium casting alloys have been restricted due to certain inherent disadvantages such as segregation. However, segregation can be overcome by thorough mh:!ng of the melt and close temperature control or by rapid solidification of the melt, which can be achieved by squeeze casting. A more serious problem exists in service if components are subjected to a modest temperature increase to about 80°C, when there is a drastic loss of strength. It was therefore thought that the incorporation of ceramic fibres in the matrix could improve the properties of the material at modestly elevated temperatures. In the majority of engineering applications, stresses exist in more than one direction, so castings with isotropic properties are preferred and consequently reinforcement of composite in three dimensions would be necessary to maintain isotropic properties. An investigation was conducted to establish the influence of squeeze casting on the mechanical properties and structure of ZA-8, ZA-12 and ZA-27 alloys. The relationship between these factors and controlled process variables such as die temperature and applied squeeze pressure was established. The mechanical properties of the castings at room temperature and the effect of ageing at 95°C on tensile strength and dimensional changes were established. The results showed a substantial improvement in the tensile strength of the 'as-cast' squeeze cast alloys when compared with the 'as-cast' gravity die cast alloys. In the case of ZA-27 alloy, squeeze casting significantly improved ductility, which is a feature of benefit for all composite systems. The results also showed that pressure and die temperature substantially affect dimensional changes of the alloys when aged at 95°C. A major aspect of the research was the evaluation of the mechanical properties of the fibre reinforced ZA-27 alloy at elevated temperatures. Short silicon carbide fibres were randomly oriented in the matrix to obtain isotropic properties by a technique involving squeeze infiltration, followed by remelting and dispersal in the melt using specially designed equipments. Squeeze casting was used in the final stage of the composite fabrication. Castings of squeeze cast composite (with up to 10% volume fibre) and squeeze infiltrated composite (with up to 18-20% volume fibre) were produced with a sound structure and with fibres that were uniformly distributed and randomly oriented in three dimensions. It was found that the reaction between the fibres and molten alloy must be closely controlled for optimum properties of the composite. In this respect, the optimum time of contact between the fibre and the molten alloy was experimentally determined. It was found that the fibre supplied was of inferior tensile strength, which resulted in poor tensile strength of the tested composite up to a temperature of 100°C. However, the fibre brought substantial Improvement ln the tensile strength of the composite when tested at temperatures of 150 to 250°C. The modulus of elasticity of the composite was substantially improved at room temperature as well as at elevated temperature. The fatigue life of the squeeze cast composite was improved compared with squeeze cast matrix alloy (fibre-free). Squeeze cast composites with 3% volume fibre showed an Improvement in tribological properties compared with squeeze cast matrix alloy and squeeze cast and squeeze infiltrated composites with higher volume percentage of fibre. Wear of cutting tools was adversely affected by the presence of fibre.
13
Bayandorian, Iman. "Magnesium alloy strip produced by a melt-conditioned twin roll casting process". Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4506.
Testo completoAbstract (sommario):
Twin roll casting (TRC) offers a promising route for the economic production of Mg sheet, but unfortunately, it produces strip with coarse and non-uniform microstructures and severe centre line segregation. Recently, a novel magnesium strip casting process termed melt conditioned twin roll casting (MC-TRC) was developed that, compared with the conventional TRC process, emphasizes solidification control at the casting stage rather than hot rolling. This was achieved by melt conditioning under intensive forced convection prior to twin roll casting resulting in enhanced heterogeneous nucleation followed by equiaxed growth. In this study the development of TRC and MC-TRC processes and a microstructural comparison of the MC-TRC Mg-alloy strip with that of conventional TRC strip, have been investigated. Emphasis has been focused on the solidification behaviour of the intensively sheared liquid metal, and on the mechanisms for microstructural refinement and compositional uniformity in the MCTRC process. The results of the process development indicate that the MC-TRC process reduces considerably or eliminates defects such as the centre line segregation, voids and cracks at or near the strip surface that are always present in conventional TRC strip. The newly-designed homogenization treatment investigated for TRC and MC-TRC magnesium alloy strips was based on microstructural evolution obtained during heat treatment. The results of the MC-TRC strips showed a much faster recrystallization rate with finer recrystallized grains, which are due to more homogeneous and a finer grain size of the as-cast MC-TRC strips compared with the as-cast TRC strips. During down-stream processing, the effects of MC-TRC process on microstructural evolution of hot-rolled magnesium strips have been understood thoroughly by accurate control of the hot-rolling procedure during each step of strip thickness reduction. This study indicates that the MC-TRC strip requires fewer rolling steps when compared to TRC strip, thus offering reduced processing cost and carbon footprint. Mechanical properties at room temperature of MC-TRC as-cast and rolled sheets are much improved when compared with the conventional TRC as-cast and rolled sheets which can result in a higher quality of final components. The mechanical properties at elevated temperature shows for the first time that the higher elongation and lower yield strength of MC-TRC as-cast strips at a temperature close to its optimised hot-rolling temperature results in better ability for rolling and higher ductility of MC-TRC Mg strip compared with the TRC Mg strip.
14
Trosch, Tanja [Verfasser]. "Development of a Platinum Casting Alloy for Jewelry and Watchmaking / Tanja Trosch". Aachen : Shaker, 2018. http://d-nb.info/1188550594/34.
Testo completo
15
Wei, Xiaodan. "Thermal mechanical analysis of interfacial behavior in aluminum alloy wheel casting process". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46024.
Testo completoAbstract (sommario):
The focus of this project is to improve the understanding of the interfacial heat transfer behavior within the Low-Pressure Die Casting (LPDC) process, which is the main manufacturing process for A356 aluminum alloy wheels, and to develop an improved methodology/expression for calculating the heat transfer across the wheel/die interface. To formulate and assess expressions for the interfacial behavior, a 2D-axisymmetric coupled thermo-mechanical model has been developed in the commercial finite element package, ABAQUS. The model was capable of predicting the thermal history, deformation and the variation of the air gap and pressure along the wheel/die interface.
The temperature predictions of the coupled thermo-mechanical model were compared with temperature measurements obtained at Canadian Auto Parts Toyota Inc obtained on a production die. A displacement measurement setup using a high temperature eddy current displacement sensor was designed and tested in a lab setting but not employed in a plant trial due timing issues.
Initially, the coupled thermo-mechanical model was run with a temperature dependent interfacial heat transfer coefficient to obtain preliminary air gap and pressure behavior at various locations. Comparisons with the thermocouple measurements suggest that the model is able to generally qualitatively, and at some locations quantitatively, predict the temperature changes from the main physical phenomena occurring during the casting process.
The preliminary air gap and pressure predictions were used to develop a temperature, gap size and pressure dependent interfacial heat transfer coefficient based on literature review. The interfacial heat transfer coefficient was implemented in the model, and was found to improve the agreement between the model predictions and measured temperatures, but was prone to numerical convergence issues.
A new methodology of incrementally changing the interfacial heat transfer coefficient has been proposed to solve the issues. The methodology was implemented in an EXCEL spreadsheet to test it and the calculated interfacial heat transfer coefficients were found to be continuous, reflecting the effects of air gap and pressure evolution. The methodology and corresponding algorithm should be further developed for use in an ABAQUS model in the future.
16
Miehe, Anja. "Numerical investigation of horizontal twin-roll casting of the magnesium alloy AZ31". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-149625.
Testo completoAbstract (sommario):
The horizontal twin-roll casting (TRC) process is an energy saving and cost-efficient method for producing near-net-shape sheets of castable metals for light-weight production. In order to investigate the TRC process numerically, a code is generated in OpenFOAM and the commercial software STAR-CCM+ is used. Both are validated with the Stefan problem, the gallium melting test case, and a continuous casting experiment for magnesium AZ31. Different solidification models are tested that are similar to solution domain definitions and solid-fraction temperature relations. The comparison with temperature measurements of the MgF GmbH Freiberg pilot plant and the final microstructure exhibits good correlation. Sensitivity studies are carried out for thermophysical properties of AZ31 as well as pilot plant parameters. Furthermore, the rolls are incorporated into the simulation to determine the effect of a location-dependent heat-transfer coefficient. Finally, the results are compared to a second pilot plant situated at the Helmholtz-Centre Geesthacht in order to explore differences and similaritiesDas horizontales Gießwalzen ist eine energiesparende und kostengünstige Methode zur Erzeugung von Flachprodukten, die im Leichtbau verwendet werden. Um dieses Verfahren numerisch zu untersuchen wurde ein Programmcode in OpenFOAM entwickelt und die kommerzielle Software STAR-CCM+ verwendet, wobei beide mit dem Stefan Problem, dem Schmelzen von Gallium und Messdaten des Stranggusses von Magnesium AZ31 validiert wurden. Verschiedene Erstarrungsmodelle werden ebenso getestet wie Variationen des Simulationsbereiches und Feststoff-Temperatur-Verläufe. Vergleiche mit Temperaturmessdaten der Pilotanlage MgF GmbH Freiberg und der finalen Mikrostruktur zeigen gute Übereinstimmungen. Sensitivitätsanalysen werden durchgeführt, um die Einflüsse von thermophysikalischen Eigenschaften und Anlagenparametern abzuschätzen. Des Weiteren werden die Walzen in die Simulation mit einbezogen, um den Effekt eines lokal veränderlichen Wärmeübergangskoeffizienten zu beurteilen. Schließlich werden die Ergebnisse mit denen einer zweiten Pilotanlage am Helmholtz-Zentrum Geesthacht verglichen
Le laminage de coulée continue horizontal possède une faible consommation d’énergie et est bon marché pour la production des feuilles de métaux coulables utilisés dans la construction légère. Afin d’examiner ce processus numériquement, un code est généré dans OpenFOAM et le logiciel commercial STAR-CCM+ est utilisé, tous les deux sont validés en utilisant le problème de Stefan, la fusion du gallium et la coulée continue verticale de magnésium AZ31. Plusieurs modèles de solidification sont testés, ainsi que la variation du domaine de simulation, et des rélations entre la teneur en matière solide et la température. Des comparaisons avec des résultats de mesures de la température à l’installation pilote de MgF GmbH Freiberg ainsi que la microstructure donnent des bons résultats. Des analyses de sensibilité sont effectuées afin d’évaluer l’influence des propriétés thermophysiques et des paramètres de l’installation. De plus, les cylindres sont intégrés dans la simulation pour estimer l’impact du coefficient de transfert de chaleur dépendant du lieu. Finalement, les résultats sont comparés avec ceux du Helmholtz-Centre Geesthacht
17
Cao, Xinjin. "Heat treatment of liquid metal : precipitation and sedimentation processing of liquid Al-11.5Si-0.4Mg alloy". Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369168.
Testo completo
18
Duan, Jianglan. "Development of a numerical optimization methodology for the aluminum alloy wheel casting process". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57699.
Testo completoAbstract (sommario):
Aluminum alloy wheel manufacturers face on-going challenges to produce high quality wheels and increase production rates. Improvements are generally realized by modifying the wheel and die designs and continually improving the manufacturing processes. Conventionally, these improvements have been realized by trial-and-error, building on past practice or experience. This approach typically results in long design lead times, high scrap rates and less than optimal production rates. The work presented in this study seeks to reduce the reliance on trial-and-error techniques by developing a new methodology to optimize the wheel casting process through the combination of a casting process model and open-source numerical optimization algorithms. The casting process model utilized in this method was developed in the commercial finite element package Abaqus™ and was validated through plant trials. An open source optimization module Python Scipy.optimize has been employed to perform the optimization. The work focuses on optimizing the cooling conditions in a low-pressure die-casting (LPDC) process used to produce automotive wheels. Specifically cooling channel timing was selected because of the critical role heat extraction plays on casting quality, both in terms of dendrite cell size and the formation and growth of porosities. The methodology was first developed with a series of test problems ending with an L-shaped geometry that employed the major features of the wheel casting process. The most suitable approach, based on the test problems, was then applied to the optimization of a 2-D axisymmetric prototype wheel die structure. The outcome revealed that numerical optimization coupled with a state-of-the-art process model has the potential to dramatically improve the method of determining cooling channel timings while also improving the product quality and process performance. The utility of the optimization methodology was found to depend on the accuracy of the casting process model. Significant challenges remain before widespread implementation of this methodology can occur in industry. Possible directions for further developments have been identified. In summary, this study represents one of the initial applications of a numerical optimization methodology to wheel casting, and that with further development; it will become an effective tool for process and die design optimization.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
19
Kavanagh, Alan. "Study of improved casting methods for the manufacture of medical grade cobalt alloy". Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7488/.
Testo completoAbstract (sommario):
Within many foundries, poor mould design and casting methods result in high levels of process variability, poor metal yield, scrap and inefficiencies leading to overall sub-optimal performance. The aim of this project was to try to try to address main problem areas through an alternate casting method (1-tree casting) used for the manufacture of ASTM F-75 cobalt chrome (Co-Cr) biomedical castings. The mould filling of various runner systems was assessed using real-time X-ray imaging and computational modelling. Mechanical testing, CT-scanning and metallurgical inspection of as-cast and heat-treated test bars produced in industrial trials at the DePuy foundry were performed. Direct thermocouple measurements, thermal imaging and microstructure measurements examined the effect of casting method on solidification time and cooling rates. Numerical modelling using ProCAST casting simulation software was performed. A statistical improvement in the as-cast tensile strength was observed with the 1-tree casting method compared to the established casting method. CT analysis indicated the presence of discrete gas porosity in some specimens which was attributed to high levels of air entrainment during pouring. The occurrence rate and morphology of the observed pores is described. Post heat-treatment the differences in the as-cast mechanical properties were eliminated with no evidence of casting method observed. However elongation to fracture results in both the as-cast and heat-treated conditions were lower than expected, and pose a challenge regardless of casting method. The 1-tree casting method reduced variation in alloy cooling rates and solidification times versus the established process.
20
Fourie, Jecois. "Numerical optimisation of the gating system of a titanium alloy inlet valve casting". Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/1290.
Testo completoAbstract (sommario):
Dissertation submitted in fulfilment of the requirements for the degree
Master of Technology: Mechanical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of Technology
2014The research described in this dissertation investigates the feasibility of casting inlet valves for an internal combustion engine using Ti6Al4V alloy. The engine valves operate in an extreme environment under high thermal cycles – this requires a material that can withstand such exposures. Ti6Al4V is the most common titanium alloy with high temperature creep and fatigue resistant behaviour, however, it is not all positive. Ti6Al4V alloy also yields many difficulties with respect to processing especially when the material is cast. It is therefore important to gain a thorough understanding of the pouring and solidification characteristics of this material. The main focus of this work was to investigate and optimise feeding and geometrical parameters to produce valves that are free from defects, especially porosity. An in depth analyses of the parameters that influenced the casting quality was performed, and it was found that casting orientation, inlet feeder geometry, initial and boundary conditions all played a vital role in the final results. These parameters were individually investigated by performing detailed numerical simulations using leading simulation software for each of these cases. For each case, a minimum of ten simulations was performed to accurately determine the effect of the alteration on casting soundness and quality. Furthermore, the relationships (if any) were observed and used in subsequent optimised simulations of an entire investment casting tree. The change of geometric orientation and inlet feeder diameter and angle showed distinct relationships with occurrence of porosity. On the other hand, alteration in the pouring parameters, such as temperature and time, had negligible effect on occurrence or position of porosity in the valve. It was found that investigating individual parameters of simple geometry and then utilising these best-fit results in complex geometry yielded beneficial results that would otherwise not be attainable.
21
Venkatasamy, Vasanth Kumar. "Analysis of in-cavity thermal and pressure characteristics in aluminum alloy die casting". Connect to this title online, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1100721824.
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22
Shilvock, W. D. "The effect of alloy and impurity variation on the treatment, casting and physical properties of aluminium-silicon eutectic alloys". Thesis, University of Canterbury. Engineering, 1995. http://hdl.handle.net/10092/8133.
Testo completoAbstract (sommario):
The aluminium-silicon eutectic alloy finds widespread use in commercial light alloy foundries world-wide. The intrinsic characteristics which ensure that this traditional alloy continues in use are excellent fluidity, moderate strength, good ductility, low shrinkage, no requirement for post casting heat treatment and exceptional corrosion resistance. The latter two are particularly noteworthy as they assure the eutectic alloy finds favour in numerous roles for which the higher strength Al-7%Si-Mg alloy is less well suited.
The research reported in this thesis aimed to quantify the changes in physical and structural properties of sand-cast Al-Si eutectic alloy due to compositional variations within the specified range provided by British Standard 1490-LM6. The eutectic alloy was selected for investigation primarily due to members of the local (NZ) aluminium industry expressing concerns regarding consistent production of castings capable of surpassing the physical requirements of the BS1490-LM6 standard.
To achieve the desired aim approximately 500 standard test bars (as used in industry and specified by BS1490) were produced using conditions replicating those encountered in a small, commercial foundry. Each specimen cast was of varying composition with the major variables being Na, Sr, Ti, B, Si, Mg, Mn and Fe. Physical and structural properties including: hardness, tensile strength, ductility, 0.2% proof strength, porosity, grain size and eutectic silicon morphology were monitored for each specimen produced. The combined composition and physical/structural data were then subjected to extensive statistical analysis via multi-linear-regression. The results of the statistical analysis are presented as a series of expressions relating the measured properties to the relevant compositional variables. The sometimes complex and inter-related effects of the elements responsible for significant property variation are illustrated in both numerical and graphical forms.
The full analysis results and associated findings are too numerous to be summarised here. An example of a significant finding is that, with the exception of grain refinement, boron is detrimental to every property monitored. Almost without exception the unwanted effects of boron are already manifest at boron levels as low as 0.01%. Another finding of interest is that within the confines of the given compositional range, the controversial practice of adding manganese to counteract iron-induced embrittlement has little effect on ductility while being highly deleterious to tensile strength. Indeed the embrittling effects of iron were found to be far smaller in magnitude than anticipated given the concern which surrounds this element. This led to the conclusion that further investigation into the effects of iron on parameters such as fatigue endurance warrant investigation.
Two compromises were unavoidable in this research firstly, an inability to assess the level and hence effects of phosphorus variations, and secondly the boron additive used was not of the desired type. Surprisingly, the effects of boron mentioned above were not found to be discernibly influenced by the latter compromise.
Two less significant areas of experimentation were also touched upon in the course of this research, namely the suitability of various materials for use in conditions requiring contact with molten aluminium, and the contamination and compositional variations which occur during degassing by conventional lance and tablet methods.
23
Dewhirst, Brian A. "Optimization of the heat treatment of semi solid processed A356 aluminum alloy". Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-111705-111503/.
Testo completoAbstract (sommario):
Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: microstructure; casting; Fluid Bed; Quality Index; Aluminum; A356; heat treatment; SSM; Semi Solid Metal Includes bibliographical references. (p.105-106)
24
Papai, Jonathan Pearson. "Contact heat transfer coefficients in aluminum alloy die casting: an experimental and numerical investigation/". The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu148784937729536.
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25
Serrano, Munoz Itziar. "Influence of casting defects on the fatigue behaviour of an A357-T6 aerospace alloy". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0117/document.
Testo completoAbstract (sommario):
L’excellente coulabilité, les coûts de production relativement bas, et ratio poids/résistance mécanique élevé des alliages de fonderie Al-Si-Mg en font une des solutions les plus intéressantes dans le secteur automobile ainsi que dans le domaine aérospatial. Toutefois, il est bien connu que la durée de vie de ces composants moulés à grand nombre de cycles (105 < Nf < 107 cycles) est sévèrement réduite lorsque des défauts de fonderie (notamment pores et oxydes) sont débouchants et/ou subsurfaciques sont présents. Ces défauts concentrent les contraintes et peuvent considérablement réduire la période d’amorçage des fissures de fatigue en fonction de leur taille, forme et des caractéristiques microstructurales du matériau. Les défauts internes (à partir desquels les fissures peuvent amorcer et propager sans interaction avec l’air ambiant) ainsi que les défauts de surface (ceux qui sont placés à la surface et en contact direct avec l’air ambiant) vont également nuire la durée de vie des composants moulés. Toutefois, dans le cas des défauts internes, les coefficients de sécurité préconisés par les règles de conception ne font pas intervenir la distance de défaut par rapport à la surface. Le suivi de fissures de fatigue effectué à la surface d’éprouvettes macroscopiques de traction indique que la présence d’un défaut avec une taille supérieure à celle des fissures microstructuralement courtes (√A ≈ 500 μm, taille contrôlée par la SDAS) produit une remarquable réduction de la durée vie. En revanche, la durée de vie n’est pas affectée lorsqu’un défaut plus petit (√A ≈ 300 μm) est présent à la surface car l’amorçage et les premiers stades de propagation sont encore influencés par la SDAS. Les essais de fatigue en torsion pure montrent que la morphologie des surfaces de rupture est fortement influencée par le niveau de contrainte. De plus, le nombre de cycles à l’amorçage est réduit par rapport à la traction. Cet amorçage est multi-site et plusieurs fissures peuvent croitre simultanément au cours de la durée de vie d’une éprouvette, la rupture finale se produisant lors de la jonction de certaines de ces fissures. La propagation des fissures en torsion est largement influencée par la cristallographie locale et les retassures ne semblent pas être des sites de nucléation préférentiels. Les durées de vie odes échantillons macroscopiques contenant défauts artificiel internes (Øeq ≈ 2 mm) sont pratiquement similaires à celles obtenues avec un matériau de référence. L’amorçage et la propagation de fissures internes a été rarement observé lors des expériences de tomographie synchrotron. Dans les rares cas où de telles fissures ont pu être observées, le chemin de fissuration semble fortement influencé par la cristallographie alors que les fissures amorcées depuis la surface se propagent globalement en mode I. La vitesse de propagation des fissures internes est très inférieure à celle des fissures se propageant à partir de la surfaceThe excellent castability, relatively low production costs, and high strength to weight ratios make Al-Si-Mg cast alloys an attractive choice for use in cheaper and lighter engineering components, in both automotive and aerospace industries. However, it is well known that High Cycle Fatigue (HCF) lives (105 < Nf < 107 cycles) of cast components are severely reduced when casting defects (notably pores and oxides) are present at the free surface or subsurface. They act as stress raisers which can considerably reduce the crack incubation period depending on their size, shape and the microstructural features of the surrounding material. Internal casting defects are of special interest to this work. The application of safety coefficients considers that all casting defects present in a component have the same deleterious effect and no attention is paid, for example, to their distance to the free surface. In other words, internal defects (corresponding to the case where the depth of the defect allows crack nucleation and propagation to essentially occur without interaction with the air environment) are considered as damaging to fatigue life as surface defects (those placed at the free surface and in contact with the air environment). Surface crack monitoring performed on uniaxial fatigue specimens indicates that the presence of a surface microshrinkage exceeding the size of microstructurally small cracks (√A ≈ 500 μm, controlled by the SDAS) readily nucleates a fatigue cracks producing steady crack propagation and remarkable reduction in the expected fatigue life. A smaller surface defect (√A ≈ 300 μm) nucleated a crack that did not reduced the expected fatigue life as in this case early stages of propagation are still nfluenced by the SDAS. Pure torsional cycling reveals that the morphology of fracture surfaces is highly influenced by the stress level. In general, torsional fatigue behaviour is described by having reduced (with respect to uniaxial testing) and multisite crack nucleation periods. Several dominant cracks can evolve simultaneously and the final failure occurs by the linkage of some of those cracks. Crack propagation is controlled by the crystallography and pores do not appear to be preferential nucleation sites. S-N curves show that macroscopic specimens containing Øeq ≈ 2 mm internal artificial defect produce similar fatigue lives to those obtained with a defect-free material. Internal crack nucleation was rarely observed during synchrotron tomography experiments; instead the fatal cracks initiated from much smaller surface defects. Tomographic images show that, in the case of internal propagation, crystallographic paths are formed while surface cracks propagate in mode I. The crack growth rate of internal cracks is much smaller than that of cracks propagating from the free surface
26
Rivero, Paz Ive. "The effect of key microstructure features on the machining of an aluminum-silicon casting alloy /". View online, 2010. http://ecommons.txstate.edu/engttad/1.
Testo completo
27
Agarwal, Pratik, e Pallav Sahu. "Microstructure and Properties Of Az91 Magnesium Alloy". Thesis, 2015. http://ethesis.nitrkl.ac.in/7803/1/2015_BT_microstructure_Agarwal.pdf.
Testo completoAbstract (sommario):
Magnesium is the lightest structural metal present on Earths surface. With a density of 1.74g/cc, it gives a high strength to weight ratio. This has made it very useful for many applications like automobile, aeronautical etc. Magnesium has many limitations and because of which it cannot be used directly as a replacement of steel and aluminium. Many alloys of magnesium have been developed to partially or completely overcome the limitations of magnesium without sacrificing other properties. One of the most commonly used commercial alloys is magnesium alloy AZ91, which gives better properties than magnesium. In this project, microstructure and properties of AZ91 in two different casting conditions is compared. The microstructure is observed under the optical microscope. The hardness is measured by Vickers hardness tester. The wear resistance of the sample is compared. The SEM analysis of the wear tested sample is observed. The approximate corrosion rate is also calculated and compared.
28
Kesavan, Arjun Rajiv. "Microstructure and creep properties of MRI230D magnesium alloy". Thesis, 2014. http://ethesis.nitrkl.ac.in/6368/1/e-38.pdf.
Testo completoAbstract (sommario):
The dependency of creep behaviour on the as-cast microstructure of MRI230D Mg alloy produced by ingot casting (permanent mould casting) and high pressure die casting was investigated. A detailed microstructural characterisation and study of creep properties have been accomplished. The alloy in both ingot-casting (IC) and high pressure die-casting (HPDC) conditions consists of á-Mg, C36 ((Mg,Al)2Ca) and Al-Mn rich phases. Microstructural study revealed finer grain size, closely spaced network and increased volume fraction of secondary eutectic phases for HPDC specimen when compared to that of the IC specimen. The grain size variation and denser network of eutectic phases was due to the considerable difference in cooling rate, high degree of undercooling associated with the faster cooling rate following HPDC facilitates the formation of a large number of nuclei in the liquid Mg alloy. The eutectic C36 phases were also observed to be coarser in the case of IC specimen owing to the slower solidification rate. Porosity was discovered significant in the HPDC specimen in comparison to the negligible extent in IC specimen. Following creep tests at 70 MPa stress level and temperature of 175°C and 200°C the HPDC specimens exhibited superior creep resistance as compared to the IC specimens. The significant creep resistance exhibited by the HPDC specimen was primarily due to the dispersion strengthening effect offered by hindering of dislocation movement at the grain boundaries. Stress dependence on the strain rates for the alloys cast by both the technologies were studied and deduced that the dominant creep mechanism was dislocation creep. The same was theortically confirmed from the deformation mechanism map established for Mg alloys. Post creep microstructural studies revealed increased precipitation of C36 phase at the grain boundaries. Larger amount of precipitation was observed in the HPDC specimens due to enhanced pre-existing eutectic phases in the same.
29
Kini, Anoop Raghunath. "Semisolid Die Casting of Wrought A6061 Aluminium Alloy". Thesis, 2013. http://etd.iisc.ac.in/handle/2005/3317.
Testo completoAbstract (sommario):
The mechanical properties achieved with high performance wrought aluminium alloys are
superior to cast aluminum alloys. To obtain an intricate shaped component, wrought alloys are commonly subjected to forging followed by subsequent machining operation in the automobile industry. As machining of such high strength wrought aluminium alloys adds to cost, productivity gets affected.
Shortening the process by near net shaped casting would tremendously enhance productivity. However, casting of such alloys frequently encounter hot tear defect. Therefore, circumventing hot tear to
successfully die cast near net shaped wrought alloy components is industrially relevant. A recent advanced casting process, namely ‘Semisolid Die casting’, is proposed as a likely solution.
Hot tearing originates due to lack of liquid flow in the inter-dendritic region. To reduce hot tear susceptibility, fine and non-dendritic grain structure is targeted, amenable for processing by semisolid
route. For semisolid processing an adequate freezing range for processing is required. Accordingly A6061 wrought alloy whose composition is tuned with higher silicon and magnesium content within the grade limits, is chosen for the study.
With the objective of obtaining fine and non-dendritic microstructured billets, electromagnetic stirring (EMS) and cooling slope (CS) methods are employed. On conducting a parametric study with
EMS, a finest possible primary α-Al grain size of about 70 μm is obtained at low stirring time at stirring
current levels of 175 A and 350 A, with the addition of grain refiner. CS, on the other hand, rendered a grain of 60 μm at a slope length of 300 mm at a slope angle of 45° with grain refiner addition. Of the two methods, CS billets are chosen for subsequent induction heating. A 3-step induction heating cycle has been devised to attain a temperature of 641°C in the billet on the basis of factors including coherency
point, viscosity of the slurry and solid fraction sensitivity with temperature. The billet microstructure is found to be homogenous throughout after quenching in water. The characterization of phase along
primary α-Al grain boundary and its composition analysis is done by SEM and EPMA respectively, after billet casting as well as induction heating. In addition, the bulk hardness is determined in BHN.
The induction heated billets are semisolid die cast to produce an engine connecting rod used in automobiles. The microstructure is characterized at various locations, and is found to consist of smooth
α-Al grains in a background matrix of fine grains formed due to secondary solidification. The component
hardness is found to be 66 BHN comparable with A6061 alloy under T4 heat treated condition. X-ray radiography does not confirm presence of surface hot tear, which is the normal defect associated with casting of wrought aluminium alloys. No defects are observed along the constant cross-sectional area of the connecting rod, suggesting that the processing could be suitable for semisolid extrusion.
30
Kini, Anoop Raghunath. "Semisolid Die Casting of Wrought A6061 Aluminium Alloy". Thesis, 2013. http://etd.iisc.ernet.in/2005/3317.
Testo completoAbstract (sommario):
The mechanical properties achieved with high performance wrought aluminium alloys are
superior to cast aluminum alloys. To obtain an intricate shaped component, wrought alloys are commonly subjected to forging followed by subsequent machining operation in the automobile industry. As machining of such high strength wrought aluminium alloys adds to cost, productivity gets affected.
Shortening the process by near net shaped casting would tremendously enhance productivity. However, casting of such alloys frequently encounter hot tear defect. Therefore, circumventing hot tear to
successfully die cast near net shaped wrought alloy components is industrially relevant. A recent advanced casting process, namely ‘Semisolid Die casting’, is proposed as a likely solution.
Hot tearing originates due to lack of liquid flow in the inter-dendritic region. To reduce hot tear susceptibility, fine and non-dendritic grain structure is targeted, amenable for processing by semisolid
route. For semisolid processing an adequate freezing range for processing is required. Accordingly A6061 wrought alloy whose composition is tuned with higher silicon and magnesium content within the grade limits, is chosen for the study.
With the objective of obtaining fine and non-dendritic microstructured billets, electromagnetic stirring (EMS) and cooling slope (CS) methods are employed. On conducting a parametric study with
EMS, a finest possible primary α-Al grain size of about 70 μm is obtained at low stirring time at stirring
current levels of 175 A and 350 A, with the addition of grain refiner. CS, on the other hand, rendered a grain of 60 μm at a slope length of 300 mm at a slope angle of 45° with grain refiner addition. Of the two methods, CS billets are chosen for subsequent induction heating. A 3-step induction heating cycle has been devised to attain a temperature of 641°C in the billet on the basis of factors including coherency
point, viscosity of the slurry and solid fraction sensitivity with temperature. The billet microstructure is found to be homogenous throughout after quenching in water. The characterization of phase along
primary α-Al grain boundary and its composition analysis is done by SEM and EPMA respectively, after billet casting as well as induction heating. In addition, the bulk hardness is determined in BHN.
The induction heated billets are semisolid die cast to produce an engine connecting rod used in automobiles. The microstructure is characterized at various locations, and is found to consist of smooth
α-Al grains in a background matrix of fine grains formed due to secondary solidification. The component
hardness is found to be 66 BHN comparable with A6061 alloy under T4 heat treated condition. X-ray radiography does not confirm presence of surface hot tear, which is the normal defect associated with casting of wrought aluminium alloys. No defects are observed along the constant cross-sectional area of the connecting rod, suggesting that the processing could be suitable for semisolid extrusion.
31
CHIANG, TSO CHUNG, e 蔣作群. "The reaserch of casting and anodizing for aluminum alloy". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/08240296473611572335.
Testo completoAbstract (sommario):
碩士國立中央大學
機械工程學系
85
AbstractThe purpose of the research is to improve the capability of casting ,welding and coloring anodized aluminum of two different materials , such as Al-Mg 514 cast alloy aluminum and Al-Zn-Mg 7005 extrusion aluminum. Since casting a 514 alloy thin rectangular test plate (250㎜×120㎜×4 ㎜)for welding was not easy , the author adopted four methods for casting and did many tests to solve it. Subsequently the property of 514 alloy was promoted by using various homogenization treatments and adding grain refiner , degassing and altering cast conditions , controlling the flow rate of melt alloy to reduce the phenomenon of shrinkage and hot tearing and enhance the mechanical properties of 514 alloy . The suitable cast conditions are recommended：(1)the temperature of melted aluminum alloy be controlled in the range from 770℃to 810℃(2) the temperature of mold be controlled in the range from 350℃to 370℃.The influence of adding alloy element and altering homogenization treating temperature was observed by means of Optical Microscope(OM), Scanning Electron Microscope(SEM), and Multiple tensile test(MTS).With altering various homogenization temperatures and adding alloy Al-Ti-B refiners and zirconium alloy elements, the results showed that mechanical properties of 514 alloy could be improved effectively . For 514 alloy ,higher homogenization temperature (450℃~490℃)was better than lower homogenization temperature (410℃~430℃). In observing microstructure of 514 alloy , it was interesting to find that the higher homogenization temperature was , the lower the eutectic phase in microstructure was , and the refiner in microstructure region observed was.In the mean time , adding the Al-Ti-B refiners and Zr adequately ,the tensile strength and elongation of the specimens will be excellent .The SEM fractograph inspections of tension failure areas were also applied to check the fracture morphology , which indicated that the fracture was of a typical ductile fracture .Choosing a proper filler , either 4043, 5183, 5356 , or so on , to weld two different materials was very important . After comparing the results of various welded specimens , it was found that the 5356 filler worked better than the others in coloring match if theoperating conditions were in the range from 134 to 156 amp and from 13 to 14.5v.Finally , to make sulfuring acid anodizing aluminum have excellent corrosion and wear resistance , it was oxide coated in the following conditions : (1)the concentration of sulfuric acid is 15％(165g/l) , (2) the operating temperature is 17℃, and (3) the operating time is 50 min.
32
Lee, Chih-Min, e 李智銘. "Investigation of Oxidation and corrosion of casting Ti-Alloy". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/87148907956119674970.
Testo completo
33
LIN, GUAN-YI, e 林冠億. "Application of CAE in Aluminum Alloy Tilt Gravity Casting". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/h89y4x.
Testo completoAbstract (sommario):
碩士逢甲大學
機械與電腦輔助工程學系
106
The objective of this research is to evaluate the effectiveness of gating design and misrun problem caused by back pressure of the A356 aluminum alloy tilt gravity casting vent using the foundry CAE software, ProCAST. The metallographic microstructure and hardness variation of A356 aluminum alloy casting through melt treatment to heat treatment are also evaluated. The simulation result shown that unpressurized gating system with gating ratio of “1:1.7:3.52” has a lower flow speed than “1:1.7:1.13”. Flow speed decreased about 18%. The molten aluminum flow gets steady when pouring. The simulation result is in good agreement with the actual result when “back pressure” is included in the simulation. The simulation showed that increasing vent area will help to solve the misrun problem. The correction value of “back pressure” is 0.067atm in this simulation result. The metallographic microstructure results of the casting at each process shown that ingot has a partial effect of modification and refinement when contenting 0.025% Sr and 0.025% Ti. After modification treatment and refinement treatment, the refinement effect of eutectic silicon and grain size were increased. The hardness of casting had a great promote after T4 heat-treatment and T6 heat-treatment. The CAE simulation method saved 63% of time and 40% of cost when compared with the tradition “Trail-and-Error” method.
34
Phani, Akella Siva Durga. "A Comparative Study of the Sn-Ag, Sn-Zn, Sn-Cu, Sn-Bi Lead Free Solder Alloys with the Commercially Available Sn-Pb Solder Alloy". Thesis, 2016. http://ethesis.nitrkl.ac.in/8079/1/2016_M_Tech_711MM1132_A_Compararative_Study.pdf.
Testo completoAbstract (sommario):
As soldering controls the effective usage and processing of electronic components in applications and devices. Solders are used as interconnect materials in microelectronic packaging. Traditionally Pb-Sn eutectic alloys have been used due to its low melting point and good wettability. However, due to the toxic nature of lead (Pb) and it harmful effect on environment and health the usage of Pb in solder should be avoided. This is why there is a need to develop environmentally benign Pb-free solders (LFS).In this research work four different lead free solder alloys, Sn-Cu, Sn-Ag , Sn-Bi , Sn-Zn, and Sn-Pb are developed and characterized. Eutectic Sn-0.7 wt. % Cu, Sn-3.5 wt. % Ag, Sn-57 wt. % Bi, Sn-8.8 wt. % Zn and Sn-37 wt % Pb solder alloys have been developed by melting and casting route. A comparative study of all the five alloys was done based on their microstructure and various properties like electrical resistivity, hardness, fractography and wettability on Cu substrate. Their microstructure of the alloys was analyzed using optical microscopy and scanning electron microscopy (SEM). The various phases in the alloys were analyzed using energy dispersive x-ray spectroscopy (EDS) attached to the SEM. The nature of fracture in the alloys was analyzed using SEM. The melting point of the alloys was determined using differential scanning calorimeter (DSC). Hardness of the alloys was determined using a Vicker‟s microhard ness tester. The wettability of the solder alloys on Cu substrate was analyzed using SEM. Electrical resistivity of all the alloys were determined using a four point electrical probe. The objective of this study is to find out the solder alloy among the four eutectic solder alloys chosen here which could replace the traditional Sn-Pb solder alloy.
35
Kumar, Punit. "Modification of Az91 Magnesium Alloy for High Temperature Application". Thesis, 2015. http://ethesis.nitrkl.ac.in/7843/1/2015_MT_Modification_Punit_Kumar.pdf.
Testo completoAbstract (sommario):
In recent years, the lightweight requirement has become crucial in aerospace and automobile application. Mg alloys provide an excellent alternative to conventional structural metals and alloys as it has the highest specific strength. Mg-alloy AZ91 (Mg-9Al-0.8Zn-0.2Mn) is the most favored alloy, being used in approximately 90% of all magnesium cast products. It has good castability, excellent room temperature (RT) mechanical properties and has low cost compared to other Mg-alloys. However, above 120°C its mechanical properties deteriorate because of the low softening temperature of same ß-Mg17Al12 which provides it better RT mechanical properties. The present study is an attempt to improve the creep strength of AZ91 through the addition of alloying elements which form thermally stable intermetallics and pins the ß-Mg17Al12. The effects of individual and combined additions of Sb and Sr on the microstructure and creep properties of squeeze-cast Mg-AZ91 alloy have been investigated. For comparison, the same has also been studied on the as-cast AZ91 alloy without any addition. The results indicate that individual and combined addition of Sr and Sb refine the grain size, ß-Mg17Al12 phase, and it affects the dynamic precipitation of ß-Mg17Al12 during creep. All the alloys have been creep tested at a temperature of 175°C and a stress level of 70 MPa. The lowest steady state creep rate is obtained in the AZ91 alloy pertaining combined addition of both Sb and Sr owing to the presence of relatively lower amount of ß-Mg17Al12 phase and high melting point intermetallics Mg3Sb2 and Al4Sr phase.
36
Dehury, Ranjit Kumar. "Impression Creep and Corrosion Behaviour of MRI230D Magnesium Alloy". Thesis, 2016. http://ethesis.nitrkl.ac.in/9320/1/2016_MT_RKDehury.pdf.
Testo completoAbstract (sommario):
Impression creep and corrosion behaviour of the MRI230D alloy have been investigated. The impression creep experiments are carried out in the temperature range 150-225oC and stress range 225-325 MPa by impressing a cylindrical indenter on the surface of specimen. Microstructure of MRI230D consists of α-Mg phase, (Mg,Al)2Ca (C36) phase and few Al-Mn-rich phase. All the creep plots exhibit a well-defined primary creep followed by secondary (steady state) creep. Tertiary stage is missing in all the plots owing to the compressive nature of the tests. The values of stress exponent (n) vary from 5.0 to 5.4 and the values of activation energy (Q) vary from 75 to 85 kJ/mol, which confirms dislocation climb controlled by pipe diffusion is the dominant creep mechanism in the MRI230D alloy in the temperature and stress levels employed. The results of XRD and microstructural observation of the as-cast and creep tested specimens conclude that the superior creep resistance of the MRI230D alloy due to the presence of the thermally stable C36 phase along grain boundaries. Electrochemical corrosion tests at 5% NaCl with pH 11 are carried out on the MRI230D alloy and results are compared with that of AZ91 alloy. The MRI230D alloy exhibits better corrosion resistance owing to the absence of Mg17Al12 phase in it.
37
Mishra, Srimant Kumar. "Ratcheting and ratcheting-creep interaction in A356 aluminium alloy". Thesis, 2018. http://ethesis.nitrkl.ac.in/9404/1/2018_PhD_SKMishra_513MM1001_Ratcheting.pdf.
Testo completoAbstract (sommario):
In automobile sectors, particularly inner turbo frame, engine blocks, pistons etc. and in aerospace industries the components like pistons, brackets, pulleys, wheels etc. are fabricated from the cast A356 aluminium alloy. Most of these components are frequently exposed to cyclic loading at elevated temperature and the major cause behind failure of such components is fatigue as well as creep. Fatigue damage becomes much more severe when the cyclic loading is asymmetric in nature; this kind of loading causes build-up of plastic strain in the structure during each cycle and thus, causes premature failure. The phenomenon is commonly known as ratcheting. On the other hand, high temperature exposure may enforce pre-mature failure of such components due to creep deformation. Situation becomes more vulnerable when ratcheting and creep occur simultaneously. Considering the importance of static and cyclic plastic deformation in structural integrity of components, extensive research work has been carried out by several researchers to understand ratcheting fatigue, creep and fatigue-creep interaction of various materials. However, the study of ratcheting behavior of A356 Al alloy has not been reported. Also, most of the existing fatigue-creep interaction studies of various aluminium alloys are concentrated on the influence of dwell time in combination with fatigue. However, the effect of previous ratcheting on creep behavior of materials has not been studied so far. It was also noticed that, as per the best possible knowledge of the author, the use of Artificial Neural Network (ANN) based prediction tool to predict ratcheting, creep and ratcheting-creep interaction was not reported in open literature. In view of this, the primary aim of the present work was to understand the ratcheting behavior, creep behavior and ratcheting-creep interaction of the A356 aluminium alloy. In association, the extent of dislocation density and its character in differently deformed specimens were evaluated using X-ray diffraction (XRD) profile analysis. Finally, ANN technique was used to asses various properties of the alloy.
Ratcheting behavior of the as-received A356 alloy was studied at ambient temperature under different combinations of mean stress (σm) and stress amplitude (σa). The values of σm and σa were chosen in such a manner that the applied cyclic loading must be in tension-tension mode. Prior to the ratcheting tests, few basic physical and mechanical characterizations of the selected alloy were carried out. Substructural variations due to ratcheting were assessed using transmission electron microscope (TEM).
In addition, the effect of accumulated ratcheting strain (after 2000 cycles) on tensile properties of the specimens was studied together with fractographic examination. In order to understand ratcheting-creep interaction, impression creep tests were carried out on asreceived as well as pre-ratcheted specimens at different combinations of applied stresses and temperatures. Dislocation density was estimated from XRD profile analysis using modified Williamson-Hall approach. All the XRD scans were done from 20 – 110 degrees using very slow scan rate (0.2º / min) near all the well identified peaks. Finally, the ANN technique was used to predict the fatigue life and ratcheting-creep interaction of the investigated alloy within and beyond the experimental domain.
The highlights of this investigation can be summarized as: (i) increase in the magnitude of a and /or m resulted an increased accumulation of ratcheting strain. The observed increase in strain accumulation was correlated with increased cyclic damage as well as with increased dislocation density in the ratcheted specimens; (ii) the postratcheting tensile specimens exhibited higher tensile properties as compared to the asreceived one. The increase in yield strength and ultimate tensile strength was attributed to occur due to increased cyclic hardening due to ratcheting; (iii) all the ratcheted specimens showed higher creep rate as compared to that of the as-received ones due to the work softening that took place during impression creep test of ratcheted specimens. On the other hand, superior creep resistance of as-received alloy resulted due to work hardening during creep test. Also, among the ratcheted specimens, the specimen that accumulated lowest ratcheting strain showed highest creep rate; (iv) the dislocation density of the tensile deformed, ratcheted and crept specimens were more as compared to the as-received one. While on the other hand, the ratcheted + crept specimens exhibited lower dislocation density than the only ratcheted specimens. These observations were explained by dislocation annihilation owing to reverse loading during impression creep. Dislocation characters indicated screw dislocation dominance on the ratcheted specimen while edge dislocations were more in the crept and ratcheted + crept specimens; (v) predictive model based on ANN approach predict and simulate the fatigue, creep and ratcheting-creep interaction response of the A356 Al alloy successfully under various test conditions within and beyond the experimental domain.
38
(7041476), Mohamadrusydi B. Mohamadyasin. "DEVELOPMENT OF HIGH DUCTILITY ALUMINUM ALLOYS FOR DIE CASTING". Thesis, 2019.
Cerca il testo completoAbstract (sommario):
Aluminum-Silicon (Al-Si) alloys are often preferred in the die casting industry due to excellent castability, high strength, corrosion resistance and low cost. Commonly, iron (Fe) is alloyed with the alloys to prevent die soldering. However, the addition of Fe in most of Al-Si alloys leads to formation of the intermetallic β-AlFeSi. The β-AlFeSi is harmful to the alloy structural integrity due to its needle-like morphology that creates stress concentration at the microscopic level. The phase presence is unfavorable to the mechanical properties and significantly reduces the elongation of the alloys. This research attempted to find viable way to control the morphology and formation of the β-AlFeSi phase.
Thermodynamic simulations were done to investigate the sequence of intermetallic formation and other phases at different alloy compositions. The analysis of solidification paths of different alloys provided the correlation between the phase formation sequence and the fraction of the β-AlFeSi phase. The analysis also identified the feasible region of alloy design for minimizing the β-AlFeSi formation. Based on the thermodynamics simulation analysis, five alloys of different compositions were designed to validate the finding of the simulation.
The tensile test results of the alloys indicated that lowering the Fe content increases the elongation of the alloy. The results also showed that elongation was reduced with the increase of Si level due to the formation of eutectic Silicon. The change of both Fe and Mn did not significantly affect the mechanical property of the alloy when the ratio of Fe to Mn was constant. Microscopic analysis showed that lowering the Fe level had effectively altered the morphology of the β-AlFeSi needle like structure. The β-AlFeSi was found to be smaller in terms of size when Fe is lower, subsequently reducing the probability of β-AlFeSi phase to be stress riser and crack initiation.
The influence of heat treatment to the mechanical property of the alloys was also studied. The mechanical result on the heat-treated samples indicated that heat treatment is a viable method to improve the elongation property of the alloy. Microscopic observations showed that the β-AlFeSi phase was broken into shorter structures over the solution heat treatment process, resulting in better elongation.
39
Huang, Bo-Zhi, e 黃柏智. "Evaluation on the Effect of Casting and Metallurgical parameters on the A356 Alloy Casting by Using the Pep-Set Casting Process". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/38188856322773175537.
Testo completoAbstract (sommario):
碩士逢甲大學
機械工程學所
91
This research investigated the effects of casting parameters ( addition amount of resin and hardener, grain size, PH value and moisture content of the raw material sand, etc. ) and metallurgical parameters (modification , refining of grain, degassing condition, melting temperature, etc. ) on the sand mold properties ( shear strength, permeability ) and the casting qualities ( surface quality, tensile strength, elongation) of the A356.2(Al-Si-Mg) alloy casting produced by Pep-Set casting process. The experimental results are as follows: For casting parameters, when using 30 mesh silica sand with over 1% resin, over 0.6% hardener, 0% moisture content, PH value of 7 of the raw material sand, and 40 minutes holding time after molding, we can obtain sand mold with good properties. And then the A356.2(Al-Si-Mg) alloy casting after poured also had good properties and with average surface roughness of 14.34μm. Under the same casting parameters, but using 100 mesh sand, the A356.2(Al-Si-Mg) alloy casting after poured will have better surface quality(average surface roughness is 10.91μm) but with worse properties of sand mold. Besides, it is worthy to notice that moisture content and PH value of the raw material sand can influence the properties of Pep-Set sand mold very much. When moisture content is over 0.2%, shear strength of sand mold will decrease clearly. It also will decrease shear strength of sand mold, when raw material sand property became acid. For metallurgical parameters, strontium modification can increase the tensile properties (tensile strength, elongation). When Sr content is 0.02wt%, the A356.2 alloy casting will have the best tensile properties. Excess Sr (over 0.02 wt%) will promote the formation of intermetallic compound (Al4SrSi2 and Al2SrSi2) and reduce the modification effects and coarsen the eutectic silicon, so that it leads to decrease the tensile strength and elongation. So, the optimum Sr content for A356.2 alloy casting is within the range of 0.02~0.03%. The addition of grain-refiner (Al-5Ti-B) can decrease the grain. As a result, a metallographic microstructure with fine grain size can improve mechanical properties. However, Excess Ti (over 0.2 wt%) will make the grain size refining steadily and increase the intermetallic compound (TiAl3) so that it leads to decrease the elongation. So, the optimum Ti content for A356.2 alloy casting is within the range of 0.15~0.25%. In addition, the effect of degassing will influence the quality of A356.2 alloy casting seriously and the better degassing effect will reduce the gas hole defect etc.. If melting temperature is higher, the gas absorption is more so that it will reduce the density and tensile property of the A356.2 alloy casting.
40
Kuan, Chung-Hao, e 關中皓. "Studies on Squeeze Casting and Gravity Casting in Gas Tungsten Arc Welding of A356 Aluminum Alloy". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/39512267594439091470.
Testo completoAbstract (sommario):
碩士國立中央大學
機械工程學系
85
A356 aluminum alloy of the squeeze castings and gravity castings were fusion welded with the gas tungsten arc welding process.The effects of gas flow rates,T6 heat treatment, and the type of filler metal were investigated under different welding conditions. The appearance of the welded surface under anodic treatment was also compared and analyzed. It was found that the gas flow rates greatly influenced the weld porosity and the evaporation of low boiling point alloy element (such as Mg).The resulting properties of the welding are caused by both the filler metal composition and the microstructure in the fusion zone and heat-affected zone. The result of these experiments indicated that:1.Increasing shielding gas flow rates,above 20L/ min.,was reduced weld porosity and inhibited the evaporation of magnesium.2.The extent of heat-affected zone was widened in welding under T6 heat treatment. It also concerned about hardness profile,anodic coating and grain size.3.The more content of silicon in aluminum alloy castings resulted a gray colorof appearance which under anodic treatment.
41
Wu, Chi-Yuan, e 巫吉原. "On Hot Cracking Property of Al-Zn-Mg Casting Alloy". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/00635494328585529780.
Testo completoAbstract (sommario):
碩士國立成功大學
材料科學(工程)學系
85
Wrought Al-Zn-Mg alloys possess high mechanical properties, hence it is worth to study and develop their casting materials. However, owing to their poor fluidity and feeding characteristic, Al-Zn-Mg alloys are liable to producing hot tear and porosity in casting process. The purpose of this research is to optimize an optimum composition for hot tear resistance, and to study the factors which are conducive to the hot tear resistance of the Al-Zn-Mg casting alloys. In this study, we adopt a ring casting to evaluate the hot tear, and evaluate the ability of hot tear resistance by the hot cracking susceptibility (HCS). HCS is defined as the ratio of the total cracks area to the radial cross-section area of the ring casting. The experiment result show that Al-7wt%Zn-1.5wt%Mg alloy exhibits the best ability of hot tear resistance. The HCS of Al-Zn-Mg alloys varies with Zn and Mg contents. Factor of solidification range, eutectic liquid fraction, elongation to failure in solid-liquid condition, solidification shrinkage, feeding characteristics and viscosity of alloys are correlated with the hot tear resistance of alloys. Further, microstructure observation show that grain boundary have a lot of porosities and crack propagation path is along the grain boundary. Three mechanisms can explain the hot tear：solidification shrinkage stress, liquid feeding and grain boundary sliding. The alloy induce shrinkage stress in solidification process. The alloy can reduce stress concentration by grain boundary sliding, and release the shrinkage stress.
42
ching, cheng chia, e 鄭嘉慶. "Research on the Improvement of Soundness AG40A Zinc Alloy Casting". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/37194388425793774608.
Testo completoAbstract (sommario):
碩士大葉大學
機械工程研究所碩士班
94
The defects of zinc alloy die-castings often happen due to its characters and the fast die-casting sped. This research was main mainly focus on the resolution of solving those defects in the AG40A zinc sanitary die-casting. The different designs of casting established by the CAE and the real castings by the hot chamber die-casting will be compared to reveal the optimal process used for the AG40A zinc alloy die-castings. The process parameters considered in this research include the casting pressure, the pouring temperature and the mold temperature of die. Utilizing the CAE simulation software FLOW-3D to simulate the different project of the AG40A zinc alloy will realize the flow filling and the solidification process. The distribution and position of gas porosity in the AG40A zinc alloy casting will be analyzed through the simulation of FLOW-3D for the different gating systems. The result show that the correspondence of the simulation of CAE and the practical die-castings. In addition, the vent hole and the overflow design will be suitable for decreasing the defects of AG40A zinc alloy die-castings.
43
Peter-Tseng e 曾震. "The Runner Design Study of Aluminum Alloy in Die Casting". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/27250519571431366811.
Testo completoAbstract (sommario):
碩士國立臺灣海洋大學
機械與輪機工程學系
92
Abstract Die Casting has become a common and important manufacturing operation for technology industry in Taiwan, and it has drawn a lot of attentions from both the academic and industrial research projects. One of the major phases in die casting production is the design and analysis of die-casting die that ensures higher product quality and longer die operation time. Apart from consulting past production experience, a common approach is to carry out exhausted process simulations on a computer by running reliable analysis software. In this dissertation, design parameters, including runner position, injection angle and superficial cross-section ratio, were planned to simulate different die-casting processes and determine the most appropriate die-casting die design. Temperature and pressure data on 16 positions around the die were picked and studied for their effects on the quality of the product and life of the die. Finite-element analyses were then executed to calculate the stress, strain, and deformation of the die during the casting process. Flow-3D and ANSYS were chosen for their common use in industry and proven reliable results. Key words: Die Casting, Die Design, Runner Analysis, Process Simulation
44
Chi-HeChen e 陳麒合. "Using gel casting to produce FeSiCr alloy powder molding chokes". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9mmdtr.
Testo completoAbstract (sommario):
碩士國立成功大學
資源工程學系
107
In this study, molding chokes using FeSiCr alloy powder as the raw material were prepared by gel casting, and the structures and magnetic properties of the samples prepared by dry pressing and gel casting were compared. The experimental results showed that the low-viscosity slurry used in the gel casting process can significantly improve the powder filling uniformity in the center of the coil. For the small-sized and high-inductance molding chokes, the problem of the uneven packing in the center of the coils can be effectively solved by using gel casting, thereby protecting the internal coil from being damaged and short-circuited. Therefore, the molding chokes prepared by gel-casting have higher inductance and better DC superposition characteristics than those prepared by dry pressing. However, if the viscosity of the slurry for the gel casting is too high, the packing of the center of the coil becomes worse, which leads to a lower inductance value. The proportion of the liquid binder used in the gel casting is also lower than that in molding, resulting in a higher initial permeability and the same or higher mechanical strength than that prepared by molding due to the more homogeneous distribution of the binder. It shows that molding chokes made by gel casting has a great potential.
45
Naithani, Nitin. "Characterization and Comparison of Lead Free Eutectic Sn-Based Solder Alloys and the Effect of Addition of Ni in Eutectic Sn-0.7Cu Solder Alloy". Thesis, 2017. http://ethesis.nitrkl.ac.in/9019/1/2017_MT_NNaithani.pdf.
Testo completoAbstract (sommario):
Until recently, lead-containing alloys were used widely in electronic and automotive industry. However, with the implementation of European union environmental directives, the use of such alloys has become prohibited. In this work we have studied various eutectic system like Sn-8.8 wt. % Zn, Sn-3.5 wt. % Ag and Sn-43 wt. % Bi and Sn-0.7 Cu to find best alternative of Sn-Pb solder alloy. Further we have studied the effect of Ni addition on the properties of Sn-0.7Cu solder alloy. The characterization of microstructure was done by optical as well as SEM. Energy Dispersive X- ray spectroscopy was done in order to find the various component present in the solder alloy. In order to find the melting point Differential scanning calorimetry was done. X- ray diffraction was done in order to find different phase present in solder alloy. It has been found that Sn-3.5 Ag eutectic solder alloy have highest melting point of 243.28 oC and lowest electrical resistivity of 1.91 µΩ-cm. Sn-43 Bi eutectic solder has lowest melting point of 141.60 oC and have highest electrical resistivity of 14.17 µΩ-cm. The lowest hardness was observed in the case of Sn-0.7 Cu eutectic solder alloy at 82.2 MPa whereas the highest hardness of 193.7 MPa was found in Sn-57Bi eutectic alloy. The results of the various solder alloys were also compared with the properties reported for the Sn-38.1 Pb eutectic solder alloy. The results suggest that Sn-Ag and Sn-Cu eutectic alloys are the best possible substitute for the Sn-Pb solder alloy as they have electrical resisitivities less than that of the Sn-Pb solder alloy although and their melting points are slightly higher than that of the commercial Sn-Pb solder alloy. Furthermore, the effect of Ni addition suggests that when the Ni concentration was increased the melting point and electrical resistivity increase and the hardness decreases. The results were observed to have positive effect of the Ni in enhancing the performance of the Sn-0.7Cu solder alloy.
46
(10729758), Clayton M. Kibbey. "A380 Aluminum Hot Chamber Die Casting". Thesis, 2021.
Cerca il testo completoAbstract (sommario):
A hot chamber die casting machine designed for zinc was donated to Purdue University. This
machine was slated for retrofit of components necessary for aluminum hot chamber die casting.
Existing components designed for zinc, mainly H-13 and cast iron, do not have the necessary
service life to economically produce castings due to chemical attack on machine components
from molten aluminum. Multiple systems were redesigned, including the pot, plunger,
gooseneck, furnace, and cooling lines. All components were upgraded to allow for the higher
service temperatures needed for molten aluminum, along with a niobium gooseneck and anviloy
nozzle to resist chemical attack of injection components. Once design and retrofitting were
complete aluminum alloy A380 was used in conjunction with a niobium gooseneck design to
create tensile bars. These tensile bars were subsequently tested and mechanical properties
evaluated.
47
Bhale, Pranav. "Effect of Deep Cryogenic Treatment on Microstructure and Properties of AE42 Magnesium Alloy". Thesis, 2015. http://ethesis.nitrkl.ac.in/7225/1/2015_Effect_Bhale.pdf.
Testo completoAbstract (sommario):
There has been a great interest of using magnesium (Mg) alloys in automotive industries owing to its high specific strength, high thermal conductivity, good damping capacity and good machinability. The use of Mg alloys in automobile increases fuel efficiency and reduce emissions by reducing the vehicle weight. The AE42 alloy is a promising creep resistant Mg alloy and it is suitable for application up to 175°C.
Cold treating is a very old process and is widely used for high precision parts to enhance their properties. Cold treatment can be done in 2 ways. When treatment is done at temperature down to -80°C it is called ‘Cryogenic Treatment (CT)’. On the other hand, when treatment is done at liquid nitrogen temperature (i.e., -196°C) it is called ‘Deep Cryogenic Treatment (DCT)’. Deep cryogenic treatment generally improves certain proper ties beyond the improvement obtained by normal cryogenic treatment. When CT was carried for steel, it was observed that there was complete transformation of retained austenite into marten site. Also, there was improvement of mechanical properties which can be explained by the precipitation of sub microscopic carbides as a result of the CT. When deep cryogenic treatment was carried out on steel, it showed significant increase in wear resistance. It was theorized that the increase in wear resistance was a direct result of the reduction in the amount of retained austenite and change in the carbide morphologies. Therefore, it is concluded that DCT has pronounced effect to alter microstructure and thereby the mechanical properties. The number of literature that report DCT of different kinds of steels, ZnO nanowires and pure Zr is plenty. Unfortunately, the number of literature on CT/DCT for Mg alloy is rare. Recently, CT/DCT on AZ91 and AZ31 Mg alloys resulted homogeneity in microstructure that exhibited superior wear and tensile properties. However, the precise effect of CT/DCT on properties like hardness, creep, corrosion and so on is still not clear. Therefore, in the present study, mechanical properties including wear as well as corrosion behavior of the AE42 (Mg-4Al-2RE) Mg alloy subjected to DCT is planned for investigation. For comparison the same tests will be carried out on AE42 alloy without DCT. DCT was carried out on specimens for 0, 4, 8 and 16 h. A detailed microstructural characterization of the untreated and treated AE42 alloy has been done. The specimens were prepared according to required dimensions for the above-mentioned tests. The phase analysis using XRD as well as optical and SEM micrographs were taken on the untreated and treated AE42 alloy. It was observed that with increase in DCT time the volume fraction of secondary Al4RE phase was reducing and that of primary α-Mg was increasing. Tensile, hardness, wear and corrosion tests were carried out on all specimen and its results were compared. The ductility of tensile specimens was increasing with increase in DCT time. The hardness of the specimens decreased with increase in DCT time. The wear rate increased with increase in DCT time. Corrosion specimens showed increase in corrosion rate with increase in DCT time.
48
Al-Kazzar, Haider. "Nd: YAG laser welding of ZE41A-T5 magnesium sand casting alloy". Thesis, 2006. http://spectrum.library.concordia.ca/8931/1/MR16249.pdf.
Testo completoAbstract (sommario):
Butt joints of ZE41A-T5 plates with two thicknesses (2 and 6 mm) were laser welded using 1.6 mm EZ33A-T5 filler wire and a continuous wave Nd:YAG system with variable laser process parameters; power (2.5--4 kW), welding speed (2--7 m/min), joint gap (0--0.6 mm) and defocusing distance (0 to -4 mm). Acceptable weld geometries with smooth top and bottom profiles and minor defects were produced with the open keyhole mode. The optimum laser power was 4 kW for both thicknesses, and the welding speed was 6 and 2 m/min for thin and thick plates, respectively. The suitable gap size for the 2 mm and 6 mm plates was found to be between 0.3 and 0.4 mm. The increase in welding speed reduced the FZ defects on a condition of having an open keyhole mode. The fusion zone showed significant grain refinement due to high cooling rate. No grain coarsening was observed in the HAZ. The microhardness test showed that fusion zone hardness was recovered to the value of the base metal after natural aging of around one year. The HAZ with a typical width between 1.5 and 2 mm, showed a drop in hardness compared with the BM. Tensile test showed that the optimum parameters had a joint efficiency between 85 and 95%. Moderate and high Weibull moduli were obtained for the mechanical properties and weld geometry indicating that the laser welding process seems to have good repeatability. Simulation of laser welding process was developed through combining different models and concepts that enabled to describe the keyhole and weld profile. This model shows good agreement with the experimental results.
49
Lim, Tiong-wei, e 林長偉. "Quality evaluation of AZ91D recycling magnesium alloy in die-casting process". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/86721732930185342635.
Testo completoAbstract (sommario):
碩士國立臺灣科技大學
機械工程系
95
In general die casting factory, large volume of recycling AZ91D magnesium alloy materials were used. Although the recycled manufacturing supplier’s materials meet the standard norm, due to the difference of recycled material used the quality of the die casting parts was influenced widely and the understanding of the causes are limitedly. The main purpose of this research is to understand the influences of recycling AZ91D magnesium alloy to the mechanical property and corrosion resistance of the die casting parts. By choosing three existing reputed brand AZ91D material, to compare with own manufacturing magnesium alloy by using 100% pure magnesium, mixture of 30% pure magnesium with 70% recycling magnesium, mixture of 70% pure magnesium with 30% recycling magnesium, and 100% recycling magnesium. Different testing specimens are made by ingot without fabrication and by die-casting process. Through the analysis of chemical compositions, metallography, tensile strength test, impact test, hardness test and corrosion resistance testing, we try to clarify the characteristic of different combination of magnesium. From the analysis of a large number of test data, we realign that the main compositions like Al, Mn, Zn, Si, Fe, Ni, Cu, etc. which can influence the properties of the die-casting parts. Besides, the pollution of casting oxides, plunger lubrication oil and die release agents during die-casting process and the impurities of flux and residue during smelting are also influence the properties of the parts. To widen the use of all recycling AZ91D magnesium alloy can significantly reduce the manufacturing cost. The results detained in this study can be offered to the recycled material manufacturer and die casting factory for reference.
50
LIN, H. Y., e 林宏宇. "The CAE Analyses of Riser Feedability for A356 Aluminum Alloy Casting". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/55554938667993403938.
Testo completoAbstract (sommario):
碩士大葉大學
機電自動化研究所碩士班
93
The study of riser feeding is mainly focus on steel and cast iron,but their feeding principles are not suitable for A356 aluminium Alloy.This research used the CAE software-AFSolid system to modify Caine's riser feeding rule and to measure the feeding distance of riser for A356 aluminium alloy.The flowing velocity of computer simulation result reveals the different effect of various gating ratio for gating system.The empirical model of feeding distances of risers for A356 aluminium alloy casting was also calculated by regression analysis method.In addition,this study also investigates the effects of thermal parameters on the soundness of A356 alloys casting by criteria hot spot,thermal gradient,cooling rate and solidification time.The practical castings poured by CO2 sand mold and X-ray examination were performed to understand the validity of CAE results. The results of study show that the gating system with 1:4:4 gating ratio had a stable melt flow for A356 aluminium alloy.From the prediction of defects simulated by those criteria stated above,the hot spot will be in the riser if the casting can get adeguate feeding.The greater thermal gradient and cooling rate can promote the feeding efficiency of castings and prevent the shrinkage of castings.As the solidification time of risers is longer than that of castings,the feeding will be sound.In addition,the difference between the Caine's riser feeding rule and the results of simulation shows that the sound range of riser's feeding should be modified.Through the examination of X-ray for inspecting the practical A356 step-castings and plate-castings also shows that the shrinkage positions are correspondent to the computer simulation.