Master Degree / Yüksek Lisans Tezleri

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Access Right: Open AccessSubject: search.filters.subject.Aluminum alloys

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Now showing 1 - 4 of 4
  • Master Thesis
    Processing and Characterization of Scandium Added A356 Cast Alloy
    (Izmir Institute of Technology, 2021) Öner, Cezmi; Kandemir, Sinan
    As a result of today's rapid technological developments and the rapid consumption of reserves in the world, the search for alternative materials has started. One of the biggest examples of this is wheel alloy. Ti5B1, one of the additives of the A356 Al alloy that is generally used in automobile wheels, allows to reduce the grain size in the alloy. In the event of depletion of possible Ti5B1 resources, there will be a need to use alternative materials instead. Based on this purpose, materials that can be used instead of Ti5B1 were examined. Scandium (Sc) as a rare earth element was found to be the least studied element with A356. A number of Sc-based studies with other aluminum alloys were reported and it was decided to work with this element for A356 alloy. In the thesis, the effect of Sc adjunction on the mechanical properties of A356 aluminum alloy after the permanent die casting process was investigated. Sc added to the A356 alloy at a ratio of 0.2, 0.4 and 0.6 weight percent, respectively. Optical microscopy (OM), Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were used for the microstructural analyses in this study. According to the experiments and results obtained in this study, it was observed that Sc can significantly increase the mechanical properties of the A356 alloy in terms of tensile strength and hardness values. Overall, it was found that the addition of 0.2 wt.% Sc to the A356 alloy could achieve a maximum tensile strength of 258.31 MPa compared to 242.54 MPa for the reference sample without Sc. No significant improvement in tensile strength results was observed when more than 0.2 wt.% Sc was added to the alloy. As for the hardness, the sample containing 0.2 wt.% Sc reached a maximum Brinell hardness of 75.01 HB compared to 77.58 HB for the unmodified sample. As a result, the amount of porosity increased with Sc added to the alloy, and an increase in dendrite arm lengths occurred. Due to this length in the arms, a decrease in fracture toughness occurred. In addition, there was no significant improvement in hardness.
  • Master Thesis
    Synthesis and Characterization of Aluminum Doped To Extend Cathode Life in Li-Ion Batteries
    (01. Izmir Institute of Technology, 2021) Tekin, Onur; Karabudak, Engin
    Lithium-ion batteries have an important place in meeting the energy needs and are of greater importance than their cognates, thanks to their characteristics as secondary batteries. Volumetric and gravimetric energy densities are the main features that carry lithium-ion batteries to the top. Lithium-ion batteries consist of different parts: cathode, anode, separator and electrolyte. While the anode materials are generally based on silicon, carbon and tin, the cathode materials include layered LiCoO2, spinel LiMn2O4, olivine LiFePO4, layered LiNi0,8Co0,15Al0,05O2(NCA) and layered LiNiCoMnO2 (NMC). Nmc and nca cathode materials stand out due to their high energy densities. Of course, lithium-ion batteries also have some disadvantages. A prime example of this is the capacity reductions it experiences with the increasing number of cycles. The main reasons for the decrease in capacity are; The transformation of the layered structure into spinel structure, the contamination of the Lio structure on the cathode to the electrolyte structure as a result of the side reactions that occur, damage the stable structure of the electrolyte and lead to Li loss. Metal oxide surface modification methods come to the fore in studies conducted to prevent these disadvantages. In this study, nmc structure was synthesized by reprecipitation method. Xrd, and sem analyzes of the obtained structure were taken. Al2O3 surface modification method was applied on the cathode surface. Cyclic voltammetry analyzes of the nmc structures with and without the modification applied were made with the help of potentiometry and the results were compared.
  • Master Thesis
    Development of a New Infrared Spectroscopic Method Based on Multivariate Calibration for the Determination of Aluminum and Magnesium Oxid Thickness on Aluminum Foil and Sheets Surfaces
    (İzmir Institute of Technology, 2016) Meşe, Ayten Ekin; Özdemir, Durmuş
    Surface oxidation is a general problem for certain industrial applications such as coating and painting of the finished rolled products. A detailed understanding for the oxide growth mechanism as well as the development of a simple analytical method to measure this oxide thickness is very important in aluminum rolling industry and this study aims to develop a spectroscopic method to determine the oxide thicknesses on the surface of the aluminum by using multivariate calibration and infrared spectroscopy. Two main series of different aluminum alloys (3005 and 3003BZ) were selected in this study to develop a proposed methodology which is based on the combination of Fourier Transform Infrared Spectroscopy (FTIR) with Grazing Angle ATR accessory and chemometrics multivariate calibration techniques. In order to obtain oxide thickness values, X-ray Photoelectron Spectroscopy (XPS) was used and aluminum oxide (Al2O3) and magnesium oxide (MgO) thicknesses determinations were carried out by two different multivariate calibration models which are Genetic Inverse Least Squares (GILS) and Genetic Partial Least Squares (GPLS). These models were able to predict Al2O3 and MgO thicknesses using FTIR that is faster, easier and cheaper to operate as well as from XPS. The correlation coefficients of XPS reference oxide thickness values versus FTIR-GATR based GILS and GPLS predicted values were better than 0.919 in range of 0 to 25 nanometers for Al2O3 and 0 to 35 nm for MgO. These results suggest that grazing angle FTIR-ATR spectroscopy may offer a simple and nondestructive alternative for quick determination of oxide layer thickness.
  • Master Thesis
    Investigation and Development of the Quality Control of Al-Wheel Rim Production Process
    (Izmir Institute of Technology, 2001) Çetinel, Mert; Aygün, Hacer
    With the increasing use of aluminum wheels in automotive industry, the aluminum foundry industry had to focus on the quality and reliability of the products.To produce good quality aluminum cast wheels, defects must be minimized and the quality of each production step must be controlled.The main topic of this study was to investigate the production line of a big aluminum wheel foundry and improve the quality of production using quality control tools. The production parameter data and real-time x-ray inspection results have been collected. Parameters of the machines that are involved with the production and the results of testing equipment and thermal analyzer have been recorded.To obtain effective feedback during process, a proposed flow chart of the wheel production line was developed. The process parameters which have influences on the quality of wheel were determined by using Fishbone diagrams. According to the results of real-time radioscopic inspection, it was concluded that the main defects that occur on Al wheel are gas holes, porosity and shrinkage. The locations of the defects were identified with results of inspection and evaluated by using the charts. To eliminate these defects, some outstanding remedies are given in the flow chart of Al wheel production.A predicted equation between hydrogen content and density index of gas holes in molten metal was obtained by using the Least Square Method. Analysis of variance for the single factor showed that degassing time affects the hydrogen content in the molten metal. Finally, hydrogen content and the molten metal temperature relationship was investigated by a graphical method.