278 resultados para Austenita-Metalurgia


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Tesis (Maestría en Ciencias de la Ingeniería Mecánica, con Especialidad en Materiales) - U.A.N.L, 1992

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Esse livro é parte do gigantesco esforço de Frei Velloso para oferecer aos brasileiros os melhores livros relacionados com a agricultura, a mineração, a pecuária e as artes que se podiam obter àquela época. Como relata Borba de Moraes, o esforço fracassou devido ao imenso atraso das elites brasileiras da época. A respeito do Fazendeiro do Brasil, o Governador de São Paulo informou à Corte que não conseguira vender um só exemplar da coleção e que não achava quem os quisesse levar de graça.Ressalte-se que esse exemplar não possui as sete gravuras mencionadas por Borba de Moraes.

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Gestión del conocimiento

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El objetivo de este trabajo, es el de implementar un módulo autoformativo para facilitar el proceso de aprendizaje de la asignatura Metalurgia y soldadura del Instituto Técnico Central. Antes de entrar en detalle sobre el tema, se exponen teorías

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Exposición de los métodos más comunes utilizados en la metalurgia extractiva para obtener de un mineral compuesto el material que nos interesa. Entre los procesos de extracción, uno de los más comunes es el de reducción, que puede ser de varios tipos, como la reducción por carbón, por hidrógeno o la aluminotermia, entre otros.

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Carbide reinforced metallic alloys potentially improve some important mechanical properties required for the overall use of important engineering materials such as steel and nickel. Nevertheless, improved performance is achieved not only by composition enhancement but also by adequate processing techniques, such as novel sintering methods in the case of powder metallurgy. The method minimizes energy losses in addition to providing uniform heating during sintering. Thus, the general objective of this study was to evaluate the density, hardness, flexural strength, dilatometric behavior and to analyze the microstructure of metal matrix composites based nickel with addition of carbides of tantalum and / or niobium when sintered in a conventional furnace and Plasma assisted debinding and sintering (PADS). Initially, were defineds best parameters of granulation, screening and mixing procedure. After, mixtures of carbonyl Ni and 5%, 10% and 15 wt.% NbC and TaC were prepared in a Y-type mixer under wet conditions during 60 minutes. The mixtures were then dried and granulated using 1.5 wt. % paraffin diluted in hexane. Granulates were cold pressed under 600 MPa. Paraffin was then removed from the pressed pellets during a pre-sintering process carried out in a tubular furnace at 500 °C during 30 min. The heating rate was 3 ºC/min. The pellets were then sintered using either a plasma assisted reactor or a conventional resistive tubular furnace. For both methods, the heating rate was set to 8 ºC/min up to 1150 °C. The holding time was 60 minutes. The microstructure of the sintered samples was evaluated by SEM. Brinell hardness tests were also carried out. The results revealed that higher density and higher hardness values were observed in the plasma-assisted sintered samples. Hardness increased with the concentration of carbides in the Ni-matrix. The flexural strength also increased by adding the carbides. The decline was larger for the sample with addition of 5% 5% TaC and NbC. In general, compositions containing added carbide 10% showed less porous and more uniform distribution of carbides in the nickel matrix microstructural appearance. Thus, both added carbide and plasma sintering improved density, hardness, flexural strength and microstructural appearance of the composites

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Engenharia Mecânica - FEG

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In the second half of the last century the automobile industries suffered from the petroleum crisis caused mainly by the wars in the Middle East. These crises led the automakers rethink their vehicles. One of the most important events after that was the adoption of new steels by the industry. One example is the TRIP steels (Transformationinduced plasticity). It is known that the macroscopic behavior of a material is strongly dependent on its microstructure and therefore the quantitative metallography is important to understand and relate the material properties to its microstructure. In this work, different specimens of TRIP steels were etched using LePera reagent. The obtained images were analyzed using digital processing. Using the ImageJ software the methods threshold and watershed were studied as well as a comparison with the ASTM E562 standard. The methods were compared and finally the morphological characteristics and volumetric fraction of the retained austenite and martensite phases were analyzed. The results showed that the threshold led to a higher number of identified grains with lower mean area and total area fraction than the watershed method and ASTM standard