Orientador: Noé Cheung / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-27T15:01:42Z (GMT). No. of bitstreams: 1 Faria_JonasDias_M.pdf: 8725613 bytes, checksum: 4224f8e05e9dbca09ceebfbb4e419859 (MD5) Previous issue date: 2015 / Resumo: Diversas aplicações industriais, tais como aquelas típicas dos setores automotivo e aeronáutico, que necessitam de resistência mecânica, utilizam ligas do sistema Al-Cu. As ligas do sistema ternário Al-Cu-Ag são empregadas como modelo para o estudo de ligas eutéticas ternárias, além do uso em certo número de aplicações técnicas, como a soldagem em alta temperatura de Al com liga Ag-Cu. Entretanto, não consta na literatura o estudo dos efeitos, em ligas do sistema Al-Cu solidificadas em regime transitório, nos parâmetros microestruturais e nas propriedades mecânicas em decorrência da adição de Ag. Nesse sentido, o objetivo principal deste trabalho consiste na investigação dos efeitos da adição de 4%Ag nos parâmetros de solidificação: velocidade de crescimento (VL) e taxa de resfriamento (?), na microestrutura e nas propriedades mecânicas da liga Al-4%Cu solidificada unidirecionalmente no sentido vertical ascendente em regime transitório. São apresentadas leis experimentais para as ligas Al-4%Cu e Al-4%Cu-4%Ag que correlacionam os espaçamentos dendríticos primário (?1), secundário (?2) e terciário (?3) com VL e ?. Foram realizadas análises de difração de raios-X para a caracterização das fases cristalinas presentes na microestrutura das ligas. O difratograma da liga binária detectou a presença dos intermetálicos ?-Al2Cu, Al-Cu, Al4Cu9 e Al6Fe e, para o caso da liga ternária, adicionalmente foi detectado o intermetálico ?-Ag3Al. Composições químicas de regiões do contorno da dendrita, assim como de seu interior, foram obtidas com o auxílio de um microscópio eletrônico de varredura acoplado a um sistema de análise por energia dispersiva. Diversas posições ao longo do lingote foram analisadas através da técnica de fluorescência de raios-X com objetivo de determinar o perfil de macrosegregação. Constatou-se que a microdureza não é influenciada pela variação tanto em ?1 quanto em ?2 da liga Al-4%Cu. Os intermetálicos ?-Ag2Al e ?-Ag3Al são responsáveis pelo aumento de dureza devido a sua interação com ?3 e outros intermetálicos. Observou-se que a liga Al-4%Cu-4%Ag apresentou limite de resistência à tração (?u), limite de escoamento (?e) e alongamento específico (?) superiores aos da liga Al-4%Cu / Abstract: Al-Cu alloys are used in several industrial applications, such as automotive and aerospace manufacturing, which demand mechanical strength performance. The Al-Cu-Ag ternary alloy system has been investigated to obtain a better understanding on ternary eutectic alloys besides its inherent applications, such as the high temperature soldering of Al with Ag-Cu alloy. However, studies concerning the effects on microstructure and hardness due to Ag addition on Al-Cu alloys solidified under transient conditions, are not found in literature. In this sense, the main objective of this work consists of investigating the solidification parameters such as growth (VL) and cooling (?) rate, microstructure and mechanical properties regarding the effects of adding 4wt% Ag on a Al-4wt%Cu alloy directionally solidified vertically upwards under unsteady-state solidification conditions. Experimental growth laws correlating the primary (?1), secondary (?2) and tertiary (?3) dendritic spacings with VL and ? are proposed for Al-4wt%Cu and Al-4wt%Cu-4wt%Ag alloys. X-ray diffraction analyses were performed in order to determine the crystalline phases present in the alloys microstructure. The diffractogram of the binary alloy detected the presence of ?-Al2Cu, Al-Cu, Al4Cu9 and Al6Fe intermetallics and, for the case of the ternary alloy, the ?-Ag3Al intermetallic was detected too. Chemical compositions at the boundary regions of the dendrite, as also inside the dendrite, were obtained using a scanning electron microscope connected to an energy-dispersive spectrometer system. Several positions along the ingot were analyzed through the X-ray fluorescence technique permitting the determination of macrosegregation profile. It is shown that the microhardness is not influenced by the variation in ?1 as well as in ?2 of the Al-Cu alloy. The ?-Ag2Al and ?-Ag3Al intermetallics are responsible for the hardness increase due to the interaction with ?3 and other intermetallics. It was observed that the Al-4wt%Cu-4wt%Ag alloy exhibited yield (?e), ultimate tensile strength (?u) and elongation (?) superior to the Al-4wt%Cu ones / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Global trends in automotive industry for weight reduction drives an interest for casting of structural aluminum parts. High pressure die casting (HPDC) is chosen for this purpose since it enables manufacturing of large series parts where complexity and repeatability is demanded. Aluminum alloys have hence been developed through the years to obtain suitable mechanical properties for high strength parts. These alloys have been investigated to predict the types of potential failure mechanisms during HPDC in order to determine die life through simulations. Die life prediction was performed through simulations in MAGMAsoft 5.4 with the help of a die life module, which is based on thermal stresses generated in the die material during casting cycles. Fatigue data at elevated temperature obtained from literature review of AISI H11 tool steel was complemented to the Wöhler curve in the software database. Comparison of two aluminum alloys showed that chemical composition had a major influence on die life. Chemical composition had a direct impact on solidification time and with longer solidification time, the thermal load on the die increased. Since the stress range on the die is temperature dependent, the ability of heat transfer over time proved to be critical for die life results. The most crucial process parameter to achieve a longer die life was constant cooling by tempering channels, due to their high potential to remove heat. Tempering channels and die spray also prevent the die from exceeding a critical temperature resulting in soldering formation. Mold erosion was consistently observed in the same location for all simulations.

The diploma thesis deals with the qualification of welding process of aluminum alloy EN AW-5083 H111. This aluminum alloy was used to make a Venturi tube. Therefore, a literature review has been developed dealing with the properties and use of aluminum and its alloys. The next chapter deals with the weldability of aluminum, aluminum alloys and the weldability of EN AW-5083 alloy. Part of the work is devoted to the used TIG method and its specifics when welding aluminum materials. The practical part of the thesis deals with the actual qualification of welding procedures according to the relevant standard and evaluation of production conditions according to the product standard. The last chapter deals with the overall manufacturing process of the Venturi tube.

The diploma thesis deals with the production of spacious thin-walled castings of aluminum alloys with a good surface quality. During the casting process, different types of molding sands and aluminum alloys are used. The target of the diploma thesis is to evaluate the casting surface quality, to analyse the defects and to evaluate the results.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 1977 / Vita. / Includes bibliographical references. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Materials Science and Engineering

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M. Tech. (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Though aluminium (Al) is justifiably described as a green metal with an increasing rate of application in structures, designers still restrain themselves from its applications as a load-bearing skeleton in structure due to insufficient design guidelines. This insufficient information is more with channel sections that might experience lateral-torsional buckling (LTB) when used as a load-bearing skeleton in structures. This study investigates the effects on imperfections on LTB load-carrying stability for 6061-T6 Al alloy channel section arches and proposed design guidelines. The case study focused on freestanding circular fixed end arches subjected to a transverse point load at the shear centre. The software package Abaqus was used to study a total of 110 arch models from three separate channel sections with an additional 16 arch models for validation. Sixty-six channel arches were developed at a constant length, while the remaining 44 arches were formed at constant slender ratios using 11 discrete included angles. The FE analyses methods used for the investigation were validated with existing analytical methods and showed good agreement, despite the assumptions of the bilinear curve used for material nonlinearity, initial geometric imperfections and residual stresses that presented the imperfections of the models. The different investigated factors include slender ratios, change in cross-section area, imperfections, and angles. These factors were found to have substantial impacts on the prebuckling state, which turns to impact LTB behaviour and load-carrying capacity. From arches developed at constant span length, the arches with moderately included angles (50°≤2𝛼≤90°) were found suitable for the designs against LTB, followed by the shallow (2𝛼<50°) and deep arches (90°<2𝛼≤180°) respectively. For arches developed at constant slender ratios, the deep arches were found to be more suitable in the design against LTB, followed by the moderate and shallow arches, respectively. In addition, it was realised that the change in web-flange thickness, section depth and slender ratios, had significant effects on the LTB loads magnitudes and very insignificant effects on the general behaviour across the included angles. The same occurrence was also observed on the prebuckling analyses. All the investigated channel section arches showed the imperfections to have significant impacts on the LTB loads. Arches developed at constant span length showed the maximum elastic LTB loads to have overestimated the expected real LTB loads by approximately 48 percent. While the maximum elastic LTB loads of arches developed at 𝑆𝑟𝑥⁄= 60 and 90 showed that the real LTB loads were overestimated by about 39 and 14 percent, respectively. That said, the elastic LTB loads on average overestimated the real LTB loads by over 50 percent for the arches developed at the constant span length and by only 18 percent for arches developed at the constant slender ratios.

The use of selective laser melting for AlSi10Mg has been gaining a lot of popularity, but unfortunately, there are a great deal of issues surrounding internal porosity. Hot isostatic pressing (HIP) has been used in many instances alongside a standard T6 treatment to reduce porosity, but that typically involves water quenching. The application for this project is meant for the satellite industry, which has tight dimensional tolerances and as such, water quenching is not adequate. Currently, annealing for a stress relief treatment is the only post- processing measure that does not involve water quenching. This project studied a novel direct HIP approach, whereby an argon quench is used after solution annealing. Three different cooling rates were studied within the DHIP process (DHIP-L=50°C/min, DHIP- M=200°C/min, and DHIP-H=400°C/min) and compared to specimens that were stress relieved (SR). Uniaxial tensile testing revealed that the strength and ductility of DHIP-H outperformed the SR condition. The true stress/strain results showed that all DHIP conditions had a superior true strain and true stress at fracture. All DHIP conditions and SR showed evidence of void growth and coalescence. SR fracture is driven through crack initiation, while the DHIP conditions fracture is driven through localized necking. In-situ tensile tests via scanning electron microscopy coupled with μ-DIC revealed that the DHIP conditions feature damage due to particle fracture, while the SR condition experiences strain localization along the interface of Si particles and the α-Al phase. In-situ tensile testing via XCT studied a comparative analysis between DHIP-M and SR and revealed that DHIP-M experiences more void growth and nucleation than the SR condition. / Thesis / Master of Applied Science (MASc)

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