Reactions of solid copper with pure liquid tin and liquid tin saturated with copper

In this study Cu was reacted with pure liquid Sn and liquid Sn saturated with Cu at 240,250, and 275 °C. Different microstructures were observed for different liquid Sn baths. For reaction in the Sn bath saturated with Cu, Cu 6Sn 5 and Cu 3Sn with the layered structure formed. This microstructure is very similar to that formed in reaction between Cu and pure solid Sn. The growth follows the parabolic kinetics, suggesting diffusion-controlled kinetics. The activation energy for the parabolic growth constant is also quite similar to that for the reaction between Cu and pure solid Sn. For reaction in pure Sn, the reaction produced a very thin and irregular Cu 3Sn layer and a thicker Cu 6Sn 5 layer with long protrusions into the Sn region. In addition to the diffusional reaction, Cu dissolved very rapidly into the pure liquid Sn bath. It is proposed that the non-planar structure formed in reaction with pure liquid Sn bath is due to the different dissolution and crystallization rates of Cu 6Sn 5 in liquid Sn along different crystallography directions.