Model for nonequilibrium partitioning during rapid solidification of binary concentrated solutions

Abstract

During the past several years, a great deal of progress has been made in the use of both pulsed and continuous wave (CW) lasers in materials processing. Usually pulsed laser is used for annealing semiconductors and CW laser for alloying and cladding substrate materials. Inherent rapid cooling in such processes invariably produces novel materials due to nonequilibrium segregation of solute atoms during solidification. Such nonequilibrium phenomena have drawn a lot of interest in both theoretical and applied areas of solid-state physics and materials science. Dilute solution theory is adequate to study nonequilibrium solute (dopant) segregation during laser annealing of semiconductors because the concentration of solute atoms is very small compared to that of the solvent (host) atoms. Using kinetic model of nonequilibrium solidification, several studies have been already carried out under dilute solution approximation to derive an expression for nonequilibrium partition coefficient. However, concentrated solutions are frequently encountered in laser cladding and alloying processes. The nonequilibrium partitioning of solute in binary concentrated solutions is modeled in this study, and an expression for nonequilibrium partition coefficient with only one unknown parameter is obtained.