Artículos de revistas
Growth of tertiary dendritic arms during the transient directional solidification of hypoeutectic Pb-Sb alloys
Registro en:
Philosophical Magazine. Taylor & Francis Ltd, v. 91, n. 35, n. 4474, n. 4485, 2011.
1478-6435
WOS:000298585500005
10.1080/14786435.2011.610375
Autor
Freitas, ES
Rosa, DM
Garcia, A
Spinelli, JE
Institución
Resumen
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Despite the importance of a complete characterization of dendritic patterns in castings, the availability of studies on the development of tertiary dendrite arms is scarce in the literature. In the present study, the tip cooling rate, local solidification time, primary and tertiary dendrite arm spacings have been determined in Pb-Sb alloys castings directionally solidified under unsteady-state heat flow conditions. The alloys compositions experimentally examined are widely used in the as-cast condition for the manufacture of positive and negative grids of lead-acid batteries. The initial growth of tertiary dendritic arms from the secondary branches was found to occur only for a Pb-3.5 wt% Sb alloy at cooling rates in the range 0.4-0.2 K/s, with no evidence of this spacing pattern for Pb-Sb alloys having lower solute content. Tertiary dendritic branches have been observed along the entire casting lengths for alloys of the Pb-Sb hypoeutectic range having compositions higher than 4.0 wt% Sb. It is shown that a power function experimental law with a characteristic -0.55 exponent is able to characterize the tertiary spacing evolution with the solidification cooling rate for alloys compositions >= 4.0 wt% Sb. The only exception was the Pb-3.5 wt% Sb alloy for which lambda(3) exhibited significant lower values when compared with the experimental values obtained for the other Pb-Sb alloys for a same solidification cooling rate. 91 35 4474 4485 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) FAEPEX -UNICAMP Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)