The dependence of lamellar spacing on growth rate and temperature gradientin the lead-tin eutectic alloy

Pb-Sn eutectic samples were directionally solidified under an argon atmosph ere in a Bridgman type furnace in order to determine the dependence of lame llar spacing, lambda(E), on the growth rate, V, the temperature gradient, G and the cooling rate, GV. Six samples were solidified with a constant V bu t different G and five samples were solidified with constant G but differen t V. The samples were solidified up to 10-12 cm length to ensure that the s teady-state condition was obtained, and then quenched. Grinding, polishing and etching techniques were applied to longitudinal and the transverse sect ions of the samples to observe lambda(E) using an olympus BH-2 optical and a JEOL JSM 5400 scanning electron microscopy. Approximately 300-500 transve rse lamellar spacings and 60-100 longitudinal lamellar spacings were measur ed and least-squares analysis was used to obtain the relationships between lambda(E) and V, G and GV. It was found that the value of lambda(E) decreas es as the values of V, G and GV increase and that the results are in good a greement with the results of the previous work and with the Jackson-Hunt eu tectic theory. (C) 2000 Elsevier Science S.A. All rights reserved.