In this paper, the influence of cooling rate on the undercooling of droplet solidification of metal melt has been investigated by employing the differential scanning calorimetry (DSC) method. The effect of cooling rate on the undercooling as well as its change tendency is analyzed theo- retically. It is shown that the undercooling degree increases whereas the change rate of undercooling decreases with in- creasing cooling rate. Moreover, the change tendency ap- proaches zero when the cooling rate exceedingly increased, indicating that an extremum of undercooling exists with in- creasing cooling rate.
A mathematical model for the undercooling of the metal droplet during the rapid solidification is established, by which the factors that influence the undercooling of the metal droplet during the rapid solidification are analyzed, and the parameter $\zeta = \sigma _{SL} ^3 /\left( {T_L \Delta H^2 } \right)$ is defined as the impact factor of the undercooling for the droplet solidification. Different undercoolings of droplets induced by various rapid solidification conditions are mainly ascribed to the change of the impact factor. Moreover, it is shown that the larger of ζ, the higher the relative undercooling can be gained. Meanwhile, the parameters such as solid-liquid interfacial energy σ SL and latent heat of solidification ΔH also vary with the rapid solidification conditions of droplets.
