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, λE, 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 λE 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 λE and V, G and GV. It was found that the value of λE 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.