A statistical methodology to reconstruct nucleation pathways in the Fe-Cu system

In precipitation strengthened ferritic alloys, the Fe-Cu binary system is a well-studied model system. Still, many unsettled questions remain about the early stages of bcc Cu precipitation, most of which refer to the shape and composition of the critical and post-critical nuclei. Since the critical nucleation states are hard to investigate by experimental methods, we propose a computational strategy to reconstruct precipitation pathways and identify the nucleation states making use of Monte Carlo simulations combined with Rare Event Sampling methods. The precipitation process is reproduced by Monte Carlo simulations with an energy description based on the Local Chemical Environment approach, applying efficient pair potentials, which are dependent on the chemical environment, and the Forward Flux Sampling technique. This method provides profound insight into the shape and composition of the early-stage precipitates and also the critical cluster size and shape in dependency of the temperature and supersaturation.