Navegando por Autor "KIKUCHI, Rafael Hideo Lopes"

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Acesso aberto (Open Access)
Influência das variáveis térmicas sobre os espaçamentos dendríticos terciários durante a solidificação direcional horizontal da liga Al-6%Cu
(2015-03) DIAS FILHO, José Marcelino da Silva; KIKUCHI, Rafael Hideo Lopes; COSTA, Thiago Antônio Paixão de Sousa; MOREIRA, Antonio Luciano Seabra; ROCHA, Otávio Fernandes Lima da
The Al-6wt%Cu alloy was directionally solidified and dendritic microstructure, solidification thermal variables, i.e., tip growth rate (VL), cooling rate (TR) and temperature gradient ahead of liquidus isotherm (GL) were characterized and correlated with tertiary dendritic spacings (λ3) determined experimentally. For this purpose, a horizontal solidification experimental apparatus was developed and specimens were solidified under unsteady state heat flow conditions. It was observed that power laws -1.1 and -0.55 characterize the tertiary spacing variations with tip growth rate (VL) and cooling rate (TR), respectively. Comparisons with other studies published in the literature for Al-Cu alloys solidified in upward and downward vertical directional conditions were performed.
Acesso aberto (Open Access)
On the Natural Convection in the Columnar to Equiaxed Transition in Directionally Solidified Aluminum-based Binary and Multicomponent Alloys
(Universidade Federal do Pará, 2015-12) GOMES, Carlos Henrique Ursolino; KIKUCHI, Rafael Hideo Lopes; BARROS, André dos Santos; SILVA, José Nazareno Santos da; SILVA, Maria Adrina Paixão de Souza da; MOREIRA, Antonio Luciano Seabra; ROCHA, Otávio Fernandes Lima da
In order to investigate the effect of natural convection in columnar to equiaxed transition (CET), Al-3.0wt.%Cu and Al-3.0wt.%Cu-5.5wt.%Si alloys ingots were obtained during the transient horizontal directional solidification (THDS). Aiming to analyze the effect of superheat in the formation of the macrostructure in ternary Al-Cu-Si alloy, the experiments were conducted with three superheat temperatures above the liquidus temperature of the ternary alloy. A water-cooled solidification experimental device was used. Continuous temperature measurements were made during solidification at different positions in the casting and the data were automatically acquired. Thermal analysis has been applied to determine the thermal parameters such as growth rate (VL), cooling rate (TR) and temperature gradient (GL), whose values have been interrelated with the CET. The observation of the macrostructures has indicated that the resulting thermosolutal convection combined with superheat seem to favor the transition, which did not occur in a single plane, for all ingots obtained, i.e., it has been seen in a range of positions in ingots. The addition of Si element in binary Al-Cu alloy anticipates the CET. A comparison with experimental results for CET occurrence in different growth directions has been carried out.