Using Kinetic Monte Carlo simulations to study phase separation in Alloys

Abstract

We review recent extensions of the kinetic Ising model used to investigate phase separation in binary alloys. Firstly, vacancies are included to model the diffusion of the atoms on the microscopic scale more realistically. These can change the coarsening rate and the coarsening mechanism. Secondly, the lattice is allowed to deform owing to the different sizes of the atoms and the resulting misfit between precipitates and matrix. The deformability of the lattice induces long-range elastic interactions between the atoms. These change the shape, orientation, and arrangement of the precipitates. The growth of the precipitates need not follow the RðtÞ / t 1=3 law.

Kinetics of spinodal decomposition in the Ising model with dynamic lattice liquid (DLL) dynamics

“…The first readily used option is a direct exchange of the neighboring atoms -Kawasaki dynamics [1,3]. The second option is vacancy dynamics (first simulation by Yaldram and Binder in 1991 [4]) where the only neighboring atom-vacancy exchanges are possible with the probability followed by the Metropolis rule [5][6][7][8]. These methods have been widely used for alloys in various simulations.…”

Multiscale ab initio simulation of Ni-based alloys: Real-space distribution of atoms in γ + γ ′ phase

“…Previous work on a model binary alloy showed anisotropic growth of domains using atom-atom exchange process compared to isotropic growth employing vacancy-atom exchange process [38]. A detailed MC study on a model binary alloy compared the effects of these two processes on phase separation [39]. The final domain structure and morphology were found to be independent of the process employed though the coarseningrate was found to be higher for vacancy-atom exchange compared to atom-atom exchange process.…”

A brief comment on the modeling of flow

“…The four models that I have compared here evolve after quenching towards thermodynamic equilibrium [46][47][48][49][50][51][52][53][54][55] for E = 0, while they tend to a nonequilibrium steady state for any E > 0. The system relaxation does not seem to be essentially influenced by this conceptual difference, however.…”