DETERMINATION OF VACANCY AND ATOMIC DIFFUSIVITIES IN SOLID-SOLUTION ALLOYS

A Monte Carlo procedure is applied to determine the vacancy and tracer diffusion constants in binary solid solutions. The Monte Carlo method uses vacancy jump frequencies which are calculated using an atomistic simulation method (the First Shell-Black/White model) and are tabulat ed for all possible jumps in all possible local environments. A simple r, more computationally efficient model, the First Shell-Gray model, i s also presented. Comparison of the vacancy diffusion constants, the p re-exponential factors and the migration energies in the Cu-Ni alloys obtained using the First Shell-Gray model and the more accurate but mu ch less computationally efficient Monte Carlo simulation method sugges ts that the First Shell-Gray model is adequate to predict the diffusio n behavior over the entire temperature range. The agreement between th e two models is even better at high temperatures where the differences among the Cu jump frequencies and Ni jump frequencies are not as impo rtant as at low temperatures. Therefore, treating the atoms in the Cu- Ni alloy as mean-field atoms is an adequate approximation in predictin g vacancy and atomic diffusion behavior. The effect of the temperature and alloy composition on the tracer and vacancy correlation factors a nd the short range order are also investigated. Copyright (C) 1996 Act a Metallurgica Inc.