Nucleation Kinetics of the β′′ Precipitate in Dilute Mg–Y Alloys: A Kinetic Monte Carlo Study

Abstract

The s'' precipitate is a primary strengthening precipitate in Mg-Y alloys. It nucleates as localized zigzag- and hexagonal-shaped clusters. Studies on the nucleation kinetics of s'' precipitate are scarce. In this study, we applied the kinetic Monte Carlo (KMC) approach to explore the nucleation kinetics of the s'' precipitates in the Mg-3.0 at.% Y system using a density functional theory-based interatomic potential. The time evolution of nucleation of the s'' precipitates was characterized based on the KMC results. Using these results, we predicted the existence of an optimum temperature for the formation of the s'' precipitates to be 550 K, at which the time necessary for nucleation is the shortest. Moreover, an upper temperature limit, above which the s'' precipitates cannot nucleate, was computed as 700 K. This study explains precipitate nucleation in Mg-Y alloys at an atomic level and provides the theory for obtaining an optimal age-hardening response.