Molecular dynamics simulation of excess vacancy formation during rapid solidification of pure metals

The formation of excess vacancies in the solid during isothermal rapid solidification, i.e., vacancy trapping in pure Cu, Fe, Ta, and V was investigated using molecular dynamics simulations. A comparison of the present results with previously reported results revealed that the temperature dependence of nonequilibrium vacancy concentration differs between face-centered cubic (fcc) and body-centered cubic (bcc) metals. In fcc metals, the nonequilibrium vacancy concentration increases monotonically as temperature decreases. In contrast, for bcc metals, the vacancy concentration initially increases and then decreases as the temperature drops. This difference in temperature dependence between fcc and bcc metals is closely associated with the density profile near the solid–liquid interface.