Abstract
The purpose of this paper is to investigate the effect of liquid-liquid structure transition on the solidification behaviour and solidification structure for Pb-Sn alloys. Furthermore, we attempt to control the solidification on the base of the liquid structure transition. From our prior investigation results, it is shown that a temperature-induced discontinuous liquid-liquid (L-L) structure transition could occur in some binary alloys, at a temperature range much above the liquidus. This transition is irreversible during cooling procedure. In the present paper, it has been proved that the solidification behaviour and solidified microstructure of Pb-Sn alloy depend on whether the melt is prepared above the critical temperature or under that. It is found that the solidification undercooling degree of the alloy prepared above the critical temperature is several times larger than that prepared under this temperature. High undercooling leads to a finer solidification microstructure.

Key words
Pb-Sn alloy, L-L structure transition, solidification behaviour, solidified microstructure

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