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)

It has been recently realized that atomic ordering in the liquid adjacent to the substrate (i.e., prenucleation) has a significant implication on the subsequent heterogeneous nucleation process. In this paper, we report an atomistic mechanism of heterogeneous nucleation through structural templating. Using molecular dynamics (MD) simulation, we investigated the process of heterogeneous nucleation in a model system consisting of liquid Al and fcc substrates with <111> surface orientation and varied lattice misfit. We found that heterogeneous nucleation occurs at a critical undercooling, proceeds layer-by-layer through a structural templating mechanism and finishes by creating a template (i.e., a crystal plane), which permits further growth of the new solid phase. In most cases, Shockley partial dislocations with predominant screw component are generated in the second layer, leading to a twist of the new phase relative to the substrate. Our study indicates that the energy barrier is dependent on the density of the dislocation network, which is directly related to the lattice misfit. Further, we calculated interfacial energy of the liquid/substrate interface, which increases with increasing lattice misfit. We show that potency of a nucleant particle is directly relevant to the structural property, chemical nature and surface condition of the substrate.