Phenomenon of a melt remaining liquid below its liquidus temperature without the occurrence of solidification. Supercooling may occur in case of rapid cooling or lack of crystallization nuclei (s. Nucleus, Balance of nuclei). Fig. shows idealized cooling curves with and without supercooling. In case (a), the melt reaches the solidification temperature Ts during cooling, and crystallization begins at point A' and terminates at point A". The melting heat released maintains a constant temperature and the temperature does not decrease further until after complete solidification. If, however, supercooling occurs, the temperature falls below Ts and the melt enters an instable state still remaining liquid and a supercooling AT occurs, which corresponds to the difference between the theoretical and actual solidification temperature (b). The course of the cooling curve is explained by the fact that the melting or crystallization heat is only released in the supercooled state at the start of crystallization and thus causes an increase in temperature (recalescence).
(Source: S. Hasse, editor of Gießerei-Lexikon, Schiele und Schön, publishing house for technical literature, Berlin)

  • Fig.: Cooling curves of a melt, a) undisturbed, b) with supercooling