Diffusivity studies in Fe-Cr alloys by Molecular dynamics simulations

Abstract

Point-defect concentration and diffusivities are obtained from molecular dynamics (MD) simulations. It is found that self-diffusion in BCC-Fe is controlled by vacancy mechanism at all temperatures. The results obtained is due to the fact that the equilibrium vacancy concentration is always much larger than the equilibrium interstitial concentration. Molecular dynamics simulation is performed to study the self-diffusivities of BCC-Fe and Fe-Cr alloys with composition variation from 5%, 10%, 15%, 20% and 25% Cr respectively at temperature 50 K,100 K, 300 K, 500 K, 700 K, and 1000 K in box size of dimension Å3. The temperature range has been divided into three parts: below room temperature (50 K and 100 K), above room temperature (300 K, 500 K, and 700 K) and 1000 K. This temperature range will describe better diffusivities of BCC Fe and Fe-Cr alloys system. Mean square displacement method is employed to calculate the diffusivity values of BCC-Fe and Fe-Cr alloy system. Slope of the MSD vs. timestep in the diffusive region gives the self-diffusivity values of the elements. The calculated diffusivity value is in good agreement with other MD simulation and experimental data.