Navegando por Assunto "Thermal parameters of solidification"

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Acesso aberto (Open Access)
Influência dos parâmetros térmicos de solidificação na transição colunar/equiaxial em ligas do sistema Sn-Pb sob condições transitórias de extração de calor
(Universidade Federal do Pará, 2007-07-04) MOUTINHO, Daniel Joaquim da Conceição; ROCHA, Otávio Fernandes Lima da; http://lattes.cnpq.br/0702326922309672; MOREIRA, Antonio Luciano Seabra; http://lattes.cnpq.br/0667768010106721
This work carry out a theoretical experimental study about the influence of solidification thermal parameters on the columnar to equiaxed transition of Sn 5%Pb, Sn 15%Pb, and Sn 20% Pb and Sn 25% Pb alloys during the horizontal unidirectional solidification process cooled by water which considers the solute convection effects. The tip growth rates and cooling rates have been experimentally calculated and the obtained results are compared with those of a numerical model. The columnar to equiaxed transition position is determined through the macrostructure characterization of the studied alloys. The experimental results have shown that the thermosolutal convection influences the CET occurrence. Finally, a comparative experimental study is done for the studied alloys when directionally solidified in different water-cooled systems.
Acesso aberto (Open Access)
Variáveis térmicas de solidificação, espaçamento dentríticos secundários e resistência à corrosão de ligas hipoeutéticas Al-Ni
(Universidade Federal do Pará, 2008-08-14) COSTA, Giselle Barata; SÁ, Fernando Antonio de; http://lattes.cnpq.br/8275621144223544
In this research is carried out a sequence of experiments with Al-Ni hypoeutectic alloys to analyze the upward vertical directional solidification on transient conditions of heat flow. Experimental approaches were developed to quantitative the thermal variables of solidification, as follow: local time solidification; dislocation rate of liquidus isotherms, tip cooling rates and thermal gradients. This study analyzes the dendrite secondary arms spacing in relation to solidification thermal variables and to alloy composition, beyond link these parameters with corrosion resistance of these alloys. These experimental dendrite parameters, concerning to alloys solidification as Al - 1, 1,4 and 1,8%Ni, couldn’t be compared with the main theoretical model of dendrite growth by others researches, because, to alloy studied there shortage of thermophysic properties, impossible this comparison. The corrosive behavior is analyzed by potentiodynamic polarization technique and cyclic polarization technique lead into 3,5%NaCl solution on room temperature, coarse structure dendritics tend to increase the corrosion rates of Al-Ni hypoeutectic alloys. The experimental results obtained by the corrosion tests were correlated with dendrite microstructure. This way, experimental tendencies of growth dendrite were determined to upward vertical directional solidification.