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 irradiationinduced 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.

Precipitate stability and morphology in irradiation environments

“…In the past, several models based on chemical rate theory were developed to describe the observed segregation effects taking defect-solute coupling into account. [3][4][5][6] It should be noted, however, that the general applicability of such mean field approaches is rather limited, owing to their neglect of fluctuations.…”

Ordering Intermetallic Alloys by Ion Irradiation: A Way to Tailor Magnetic Media

“…Polarized EXAFS measurements 11 revealed that this did not preclude a high degree of DSRO and significant in-plane homo-coordination. The films were irradiated at temperatures ranging from 293K to 573K with 130 keV He ions at a fluence of 2.0x10 16 ions/cm 2 . Partially masked samples confirmed that heating alone had no effect.…”

A defect-based model of radiation-induced segregation to free surfaces in binary alloys

“…In all the models mentioned above, the defect and atomic migration barriers are assumed to be independent of the local environment. Using the method developed by Grandjean [11], Allen and Was [10] proposed a model in which the migration barriers were dependent on the local atomic concentration. The other class of models, proposed by Grandjean [11], relies on a mean-field type treatment of diffusion on a discrete lattice using rate theory [12].…”

“…Using the method developed by Grandjean [11], Allen and Was [10] proposed a model in which the migration barriers were dependent on the local atomic concentration. The other class of models, proposed by Grandjean [11], relies on a mean-field type treatment of diffusion on a discrete lattice using rate theory [12]. In this framework, since the description of diffusion is atomistic, the effect of composition and short range ordering on segregation is automatically taken care of.…”