Mechanical property degradation due to the disorder to order phase transformation is of potential concern for alloys based on the Ni-Cr binary system (e.g., 690), particularly in nuclear power applications where component lifetimes can exceed 40 years. In the present research, the disorder-order phase transformation has been studied in the Ni-33 at% Cr model alloy by a combined experimental and computational approach. The multiscale modeling framework utilizes grand canonical and kinetic Monte Carlo simulation techniques based upon density functional theory calculations to treat both the thermodynamic and kinetic aspects of the phase transformation. The simulation results are used to generate a simple model for the ordering kinetics based upon the Kolmogorov-Johnson-Mehl-Avrami equation. Experimental measurements of the change in lattice parameter as a function of aging time and temperature are obtained in order to assess the model accuracy.
