Solidification of Sn-Pb Eutectic System Alloy in Sounding Rocket TR-IA-4

Abstract

The solidification mechanisms of three different compositions of Sn-Pb eutectic system alloys near and at the eutectic point were examined in space using sounding rocket TR-IA-4 on August 25, 1995. Samples were melted and solidified in an isothermal furnace. The samples were 10 mm in diameter and 10 mm in length. Three samples were melted before launch and solidified under microgravity conditions to examine whether gravitational segregation oc­cured. The other three were melted and solidified under microgravity conditions. The primary crystals distributed themselves evenly throughout the samples during flight so that homogeneously solidified structures were obtained. The solidification mechanisms of these alloys in space are considered. The results are applied to confirm the formation mechanisms of gravity segregation. It is concluded that segregation is caused by the movement of primary crystals in the liquid eutectic due to their density differences.