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Microstructure-property relationships of SiC fibre-reinforced magnesium aluminosilicatesKumar, Atul January 1994 (has links)
No description available.
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DEVELOPMENT OF HIGH DUCTILITY ALUMINUM ALLOYS FOR DIE CASTINGMohamadrusydi B Mohamadyasin (7041476) 15 August 2019 (has links)
<p>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.</p>
<p>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. </p>
<p>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. </p>
<p>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. </p>
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Estudo de tratamentos térmicos da liga Ti-15Zr-xMo / A study of the heat treatments in a Ti-15Zr-xMo alloyXavier, Caio Castanho [UNESP] 02 March 2017 (has links)
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Previous issue date: 2017-03-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O titânio, e as ligas baseadas nesse elemento, são amplamente utilizados como biomateriais, com aplicações tanto como implantes dentários quanto ortopédicos. Para isso, apresentam características importantes como: biocompatibilidade, resistência à corrosão, em geral baixo módulo de elasticidade e baixa densidade. O titânio possui uma temperatura de transformação alotrópica, que propicia o controle das propriedades da liga pela manipulação de sua microestrutura, através da adição de elementos de liga e/ou tratamentos térmicos. De fato, para ligas de titânio com uma composição definida, a realização de tratamentos térmicos, permite modificar a microestrutura da liga e, consequentemente, modificar as propriedades mecânicas do material em questão, fator essencial para o estudo em aplicações como um implante médico. O presente trabalho tem como objetivo o estudo detalhado de diferentes tipos de tratamentos térmicos de ligas do sistema Ti-Zr-Mo. Diferente de outros trabalhos da literatura, o estudo foi feito para cada tratamento térmico separadamente, analisando a microestrutura e a microdureza das ligas visando uma aplicação biomédica. Primeiramente, as ligas foram fundidas em um forno de fusão à arco voltaico, com quatro composições diferentes de liga: Ti-15Zr, Ti-15Zr-5Mo, Ti-15Zr-10Mo e Ti-15Zr-15Mo. Dessa maneira, pretendeu-se obter amostras com microestruturas de fase α, α+β e β. Através de uma análise por EDS, um estudo sobre a composição química das amostras foi realizado, sendo que, determinou-se que as ligas foram fundidas com uma boa qualidade e sem a presença de aglomerados ou segregados. A análise microestrutural foi realizada a partir de microscopias óptica e eletrônica de varredura. Para a liga Ti-15Zr, foi possível observar apenas a presença de uma estrutura acicular de fase α. Por outro lado, a liga Ti-15Zr-5Mo possui uma microestrutura de matriz β com finas agulhas de fase α nos contornos de grão. As ligas Ti-15Zr-10Mo e Ti-15Zr-15Mo apresentaram somente contorno de grão do tipo β. Para os tratamentos térmicos, houve um aumento de fase α nas condições tratadas por 600°C. No entanto, os tratamentos térmicos de 900°C e 1000°C demonstraram uma variação de fase na liga dependente do tipo de resfriamento realizado, onde o resfriamento lento obteve um crescimento de fase α. Através da análise da microdureza, percebe-se que em geral houve um aumento nos valores com o acréscimo de Mo e fase β na liga, sendo que, a liga Ti-15Zr apresentou uma microdureza entre 282-327 HV; a liga Ti-15Zr-5Mo de 331-390 HV; Ti-15Zr-10Mo apresentou valores entre 389-432 HV e a Ti15Zr-15Mo de 343-433 HV. / The element titanium and its alloys are widely used as biomaterials with applications in both dental implants as in orthopedics materials. Therefore, important features are required such as: biocompatibility, corrosion resistance, low values of Young modulus and low density. Also, titanium has an allotropic transformation temperature, which provides controlling the mechanical properties of the alloy. A microstructure manipulation can be achieved by the addition of certain alloying elements and heat treatments. In fact, for titanium alloys with a defined composition, heat treatments allow microstructure modification, hence alteration in the mechanical properties of the material, an essential subject for the study of medical implants applications. This study provides a detailed study of heat treatment conditions in a Ti-Zr-Mo system alloy. Unlike other papers in the literature, this study was done for each heat treatment separately, analyzing the microstructure and microhardness of the alloys for a biomedical application. First, the alloys were melted in an arc voltaic furnace, with four different alloys compositions: Ti-15Zr, Ti-15Zr-5Mo, Ti-15Zr-10Mo and Ti-15Zr-15Mo. In order to obtain samples with α, α+β and β phase microstructures. Through EDS analysis, a study on the chemical composition of the samples was performed. It was determined that the alloys were cast with good quality and without the presence of agglomerates or segregates. Microstructural analysis with optical microscopy and scanning electron was realized. For Ti-15Zr alloy, it was only possible to observe the presence of a lamellar structure composed of α phase. On the other hand, the Ti-15Zr-5Mo alloy has a microstructure of a β phase matrix with fine needle of α phases at the grain boundaries. The Ti-15Zr-10Mo and Ti-15Zr-15Mo alloys showed only beta type grain boundary. For the 600°C heat treatment conditions, it is noticed a growth in the α phase. However, for the 900°C and1000°C, there was a phase transition regarding the cooling rate of the heat treatment. The microhardness analysis shown that in general, microhardness increases with the Mo and β phase content of the alloy, where the Ti-15Zr alloy presented a microhardness (HV) between 282-327 HV; the Ti-15Zr-5Mo of 331-390 HV; the Ti-15Zr-10Mo showed values within 389-432 HV and the Ti15Zr-15Mo of 343-433 HV.
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Evaluation of post-weld heat treatments for corrosion protection in friction stir welded 2024 and 7075 aluminum alloysWidener, Christian Aragon 12 1900 (has links)
This dissertation presents the results of an investigation into the corrosion resistance of friction stir welding (FSW) for aerospace structures. Two of the most common aerospace aluminum alloys, 2024 and 7075, were investigated. In the as-welded condition, both alloys were found to be highly susceptible to exfoliation corrosion, and 7075 was found to be susceptible to stress corrosion cracking as well. The goal of this research was to identify proper initial temper selection and postweld aging treatments for enhancing the corrosion resistance of both 2024 and 7075 alloys, and their dissimilar joints. A large number of heat treatments were investigated for 7075 in the T6 and T73 tempers, including retrogression re-aging (RRA). Heat treatments were also investigated for 2024-T3 and 2024-T81. Samples were evaluated for resistance to exfoliation corrosion using optical microscopy. Microhardness, electrical conductivity, tension, and fatigue crack propagation tests were also performed on the samples. Beneficial heat treatments were found for both alloys as well as for their dissimilar joints. / "December 2005." / Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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Estudo da variacao da area especifica, da acidez superficial e do volume do poro de alguns bauxitos brasileiros em funcao da temperatura de ativacaoSILVA FILHO, JOAQUIM G. da 09 October 2014 (has links)
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12893.pdf: 1625501 bytes, checksum: fe39dd92498184bf046e7732940f5cc2 (MD5) / Dissertacao (Mestrado) / IEA/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP
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Investigacao do processo de endurecimento de materiais via laserBERRETTA, JOSE R. 09 October 2014 (has links)
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06047.pdf: 7935799 bytes, checksum: 59666d44ed8e3e6286af16eb865fb734 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Caracterização microestrutural, mecânica e tratamento térmico da liga AA-6082 obtida pelo processo de conformação por spray / Microstructural characterization, mechanical and heat treatment of the spray formed AA-6082 alloySIQUEIRA, GONÇALO 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:35:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:11Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Estudo da variacao da area especifica, da acidez superficial e do volume do poro de alguns bauxitos brasileiros em funcao da temperatura de ativacaoSILVA FILHO, JOAQUIM G. da 09 October 2014 (has links)
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12893.pdf: 1625501 bytes, checksum: fe39dd92498184bf046e7732940f5cc2 (MD5) / Dissertacao (Mestrado) / IEA/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP
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Investigacao do processo de endurecimento de materiais via laserBERRETTA, JOSE R. 09 October 2014 (has links)
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06047.pdf: 7935799 bytes, checksum: 59666d44ed8e3e6286af16eb865fb734 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Caracterização microestrutural, mecânica e tratamento térmico da liga AA-6082 obtida pelo processo de conformação por spray / Microstructural characterization, mechanical and heat treatment of the spray formed AA-6082 alloySIQUEIRA, GONÇALO 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:35:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:11Z (GMT). No. of bitstreams: 0 / O processo de conformação por spray é interessante devido à capacidade de conjugar, em apenas uma etapa do processo, a vantagem da técnica de solidificação rápida combinada com alta produtividade dos processos de fundição convencional. Este processo permite a obtenção de materiais livre de macrossegregações, livre de porosidades e com microestrutura refinada. A evolução recente das pesquisas está levando ao desenvolvimento de novas ligas e os resultados têm sido interessantes. O processo de solidificação rápida inerente da conformação por spray permite a produção de ligas com composições diferentes das obtidas pela fundição convencional. O objetivo deste trabalho foi o de caracterizar mecanicamente uma liga de alumínio AA-6082 conformada por spray. Os resultados de testes de dureza Vickers são apresentados para seções de um preformado em relação a sua altura (em um arranjo tridimensional). O material foi avaliado na condição como conformado por spray e após tratamento térmico de solubilização a 525 ºC por 1 h, seguido por envelhecimento a 125 ºC por períodos distintos de 1 h, 10 h, 100 h e 500 h. É mostrado que o a liga AA 6082 conformada por spray mostra uma boa estabilidade térmica em relação a variação da dureza durante o envelhecimento. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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