Short-Range Order in Fe-Cr Alloys: Lattice Monte Carlo Modelling

Abstract

Short-range order in Fe–Cr alloys is investigated by Monte Carlo method. The modelling was performed by Metropolis algorithm using the LAMMPS software package. Modelling results were analyzed by the visualization and data analysis package Ovito. The model of the alloys supposed that the lattice structure was fixed and interaction exists between the first and the second neighbours. The Fe–Cr interaction was established with the use of interatomic interaction potential Abell–Brenner–Tersoff (ABOP). Different concentrations of substitutional impurity of chromium in iron were investigated, viz. 5–50 at. %. The energy of mixing in the Fe–Cr system was calculated for various concentrations of substitutional impurity. Calculation showed that the chosen interaction potential reproduces correctly the changes of the sign of the energy of mixing as a function of Cr concentration. When applied in Monte Carlo kinetic modelling the potential predicts correctly the immiscibility of initially chaotic Fe–Cr alloys as a function of Cr content. The Cowley short-range order parameter is determined that is used for quantitative estimation of the degree of ordering. A strong tendency towards ordering in Cr distribution is observed at low concentrations which is exhibited by negative values of short-range order parameters, in accordance with the experiment.