Kinetics of Short-Range Ordering in Concentrated Solid Solutions

Chemical short-range order (SRO) has been reported to have profound impact on the properties of concentrated solid solutions. For alloy design it is thus of interest to be able to predict the time scales associated with its formation. We present comparisons of kinetic Monte Carlo (kMC) simulations of isothermal short-range ordering (SRO) and clustering (SRC) kinetics in binary concentrated alloys with a mean-field concentration-wave (CW) model. The CW model is able to give order-of-magnitude agreement with kMC simulations for ordering/clustering relaxation times over a wide range of temperatures and compositions. Interest in the CW model stems from the fact that it does not require parameterization of vacancy hopping energy barriers, which, for a concentrated alloy, becomes costly computationally. It can also be extended readily to multicomponent systems. We assess limits in the accuracy of the model, and discuss the effect of cooling rates as well as the extension to multicomponent systems. Ultimately, the simplicity and performance of the CW model compared to kMC simulations suggests that it is a useful tool to for designing thermal treatments to control formation of SRO/SRC. Research supported by the DOE-BES FUTURE EFRC.