Kinetic model for equilibrium and nonequilibrium segregation in concentrated alloys under irradiation

Abstract

We propose a mean-field lattice rate model for describing the kinetics of equilibrium as well as irradiation-induced surface segregation in concentrated alloys. The kinetics and thermodynamics are treated in a mutually consistent way. The model treats the composition field of the chemical constituents and of the point defects. The latter are nonconservative and are produced and destroyed either by the nuclear collisions in the bulk or by thermally activated exchange of the atoms with the free surface. The few adjustable parameters can be scaled to the thermodynamics and kinetics of the alloy. Published experimental segregation profiles in Ni-Cu alloy with two compositions and three temperatures are successfully reproduced with a single set of parameters: they exhibit inversion of segregation induced by irradiation.