5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

For liquid metal, heterogeneous nucleation is main channel towards the formation of solid crystal. Fine tuning of nucleation means an optimized solidification structure, and consequently promises tailored properties for application. There are a few extensively used industrial practices for nucleation tuning, as AlTiB catalyzed grain refining in Al alloys, silicon modification for AlSi alloys, spheroidization of graphite in cast iron, and so on. In new energy storage area, the nucleation control is also important for high energy lithium-ion batteries. An unexpected nucleation of lithium leads to infinite relative volume expansion presenting low cycling efficiency and even safety hazards in batteries with lithium metal electrodes. The nucleation potential of a new crystal on substrate was believe to be a function of lattice misfit between new crystal and substrate as stated by conventional nucleation theory. But as we understood, solidification is a liquid/solid transition rather than solid/solid transition, thus the lattice misfit between two crystals are hardly to elaborate the real scenario of nucleation process. The state-of-the-art analytical techniques offer the opportunities tracking the atomic structural evolution adjacent to solid-liquid interface which makes the in situ observation on heterogeneous nucleation possible. Here we report up-to-date results on in situ observed heterogeneous nucleation of a few metals on different substrates. The results indicates that the nearest neighbor distance of liquid atoms and their coordination number can be tuned by the alloying element or substrate. The prenucleated ordering structures in the liquid have a tendency to be aligned in a preferred orientation, which is templated by the lattice structure of the substrate. This prenucleated ordering structure with preferred orientation will match the atomic structure of the substrate forming new crystals. That’s the reason why the lattice mismatching, a parameter describing the matching of new crystal with substrate, is still able to predict the nucleation potential of the substrate in a given liquid. The alloying element can be used to tune the lattice mismatching at the interface through interfacial structural tuning to enhance heterogeneous nucleation in the liquid. This findings will extend the understanding on heterogeneous nucleation leading to more effective nucleation tuning approaches in casting foundries, epitaxial growth of functional metal film or even more extensive application as energy storage area.