The Dominating Mechanisms for the Formation of Solute-Rich Clusters in Steels under Irradiation

The formation of nano-sized, coherent, solute-rich clusters (NSRC) is known to be an important factor degrading the macroscopic properties of steels under irradiation. The mechanisms driving their formation is not yet fully understood. This work focuses on low-Cu steels, where solute species are contained below their solubility limit. We rationalize the processes taking place at the microstructure level under irradiation, relying on the latest theoretical end experimental evidence on atomic-level diffusion and transport processes. These are compiled in a new model, based on the object kinetic Monte Carlo (OKMC) technique. We evaluate the relevance of the underlying physical assumptions by applying it to a large variety of irradiation experiments. Our model predictions are compared with new experimental data obtained with atom probe tomography, complemented with information from the literature. The results of this study reveal that the role of immobilized SIA loops dominates the seeding processing of NSRC, while their thermal stability is described with simplifying assumptions.