Nucleation barrier height in undercooled metallic melts

The phase-field model of a liquid-to-solid transition was constructed where the model parameters were linked quantitatively to the interfacial properties, and the variation of nucleation barrier height in undercooled metallic melts with respect to undercooling was studied respectively based on two kinds of forms of local free energy density. The calculation results show that, with the increase of undercooling, the critical nucleus does not show bulk properties, and the nucleation barrier height decreases gradually and deviates more and more from that predicted by the classical nucleation theory in both cases. The physical spinodal occurs for a specific form of the local free energy density, where the nucleation barrier height vanishes when the undercooling reaches a critical value and the reduced nucleation barrier height can be expressed by a function of the ratio of undercooling to critical undercooling.