The formation of nano-sized, coherent, solute-rich clusters (NSRC) is known to be an important factor causing the degradation of the macroscopic properties of steels under irradiation. The mechanisms driving their formation are still debated. This work focuses on low-Cu reactor pressure vessel (RPV) steels, where solute species are generally not expected to precipitate. We rationalize the processes that take place at the nanometer scale under irradiation, relying on the latest theoretical and 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 the model to a large variety of irradiation experiments. Our model predictions are compared with new experimental data obtained with atom probe tomography and small angle neutron scattering, complemented with information from the literature. The results of this study reveal that the role of immobilized self-interstitial atoms (SIA) loops dominates the nucleation process of NSRC.

已知形成纳米尺寸，连贯的，富含溶质的团簇（NSRC）是导致钢在辐照下宏观性能下降的重要因素。推动其形成的机制仍在争论中。这项工作的重点是低铜反应堆压力容器（RPV）钢，通常不会在其中沉淀出溶质。我们依赖于原子级扩散和传输过程的最新理论和实验证据，使在辐照下在纳米级发生的过程合理化。这些基于对象动力学蒙特卡洛（OKMC）技术以新模型进行编译。我们通过将模型应用于多种辐照实验来评估基本物理假设的相关性。我们的模型预测与通过原子探针层析成像和小角度中子散射获得的新实验数据进行了比较，并辅以来自文献的信息。这项研究的结果表明，固定的自填隙原子（SIA）环的作用主导了NSRC的成核过程。