LAUSR

Abstract Prenucleation refers to the atomic ordering in the liquid adjacent to a liquid/substrate interface above the nucleation temperature. It provides a precursor for heterogeneous nucleation in the liquid adjacent to the interface. As magnesia (MgO) and alumina (Al2O3) widely exist in and can be potential nucleation sites for Al-Mg based alloys, we investigate the influences of the substrate surfaces, the α-Al2O3{0 0 0 1} and the Al-terminated MgO{1 1  1} on the atomic ordering in the liquid Al adjacent to the liquid-Al/oxide interfaces using an ab initio molecular dynamics simulation technique. The study reveals the formation of an Al-layer terminating the substrates. The newly formed Al-layers display structural splitting and possess atomic vacancies, being atomically rough. Consequently, there is weak prenucleation at the liquid/oxide interfaces. Analysis also exposes subtle influences of the structural and chemical properties of the oxide substrates on the prenucleation at the interfaces. The attained information sheds light on the role of oxide particles in the solidification of Al-Mg based alloys.