Molecular dynamics simulation of heterogeneous nucleation from concave cavity at surface of grain refiner

Abstract

Grain refiners are often used in practical production processes of metallic materials to promote and control nucleation. Although morphology of the grain refiner strongly affects nucleation behaviour, it is not well understood how unevenness of surface of the grain refiner affects nucleation from atomistic viewpoint. In this study, effect of concave cavity at surface of the grain refiner on heterogeneous nucleation is investigated by molecular dynamics (MD) simulation. HCP-Ti cube with a concave cavity is employed in the MD simulation as a grain refiner of the solidification of undercooled Al melt as a model study. HCP-Al solid is firstly formed at the tip or on the side wall of cavity and FCC-Al growth is followed on the exposed (0001) surface of HCP-Al for most of the cavities, whereas FCC-Al solid is directly formed on HCP(0001) terraces at the side wall of the cavity with large-obtuse apex angle.