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

Pb-Sn eutectic samples were directionally solidified under an argon atmosphere in a Bridgman type furnace in order to determine the dependence of lamellar 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 but different G and five samples were solidified with constant G but different V. The samples were solidified up to 10-12 cm length to ensure that the steady-state condition was obtained, and then quenched. Grinding, polishing and etching techniques were applied to longitudinal and the transverse sections of the samples to observe lambda(E) using an olympus BH-2 optical and a JEOL JSM 5400 scanning electron microscopy. Approximately 300-500 transverse lamellar spacings and 60-100 longitudinal lamellar spacings were measured 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) decreases as the values of V, G and GV increase and that the results are in good agreement with the results of the previous work and with the Jackson-Hunt eutectic theory. (C) 2000 Elsevier Science S.A. All rights reserved.