Supercooling During the Crystallization of Alloys in Condensed Films

Compared to supercooling of pure metals, the study of supercooling of alloys is complicated by a number of factors. Thus, the difference in temperatures of solidus and liquidus, which is natural for alloys, leads to some ambiguity in the numerical determination of the supercooling value. In addition, local segregation of components can be observed in real alloys. Due to the concentration dependence of the melting point, violation of the film homogeneity leads to a local change in the phase transition temperatures. In this connection, for studying the concentration dependence of supercooling of alloys, integral methods that allow obtaining average information about the processes in the sample become very effective. In particular, these are the methods based on the use of electrical resistance and the resonant frequency of a quartz oscillator. The chapter presents the results of the study of supercooling in various contact pairs. It is shown that in the contact pair (Bi–Sn)/Cu the concentration dependence of the crystallization temperature of the supercooled melt generally repeats the liquidus line, but lies significantly below it and the solidus line. This indirectly indicates the approximate constancy of wetting in the system. The results of the study of supercooling in (In–Pb)/Mo samples indicate that the relative supercooling reaches a maximum for alloys containing equal amounts of lead and indium. In the Bi–Sn system, minimal supercoolings are observed during the crystallization of the eutectic, located on one of its components. This confirms the general trend according to which the achievable supercooling decreases as the interaction in the system improves.