A novel hybrid model combining continuum local nonequilibrium and discrete variables methods for solute trapping during rapid alloy solidification

Abstract A novel hybrid model, which combines the advantages of micro-scale discrete approach and continuum local nonequilibrium diffusion model (LNDM), has been developed to describe solute trapping and solute drag during rapid alloy solidification with non-sharp interface. The model treats the solid-liquid interface as a region with well-defined borders, which consists of n interatomic (discrete) layers. The continuum LNDM, which is presented in Acta Mater. 93 (2015) 256–263, as well as in earlier publications, describes local nonequilibrium solute diffusion in a much wider bulk liquid region. The solute partition coefficient and the solute drag energy are studied as functions of the interface velocity, the interface width and other parameters. The model predicts that the abrupt transition to partitionless and dragless solidification occurs independently of the interface width and the equilibrium partition coefficient KE at a finite interface velocity VD. The complete solute trapping velocity VD is a purely diffusion parameter, whereas the mid-transition velocity between KE and the complete solute trapping K = 1 depends on the interface width and KE.