Investigating the synergistic evolution of H and He with irradiation defects in Fe by a new Fe-H-He ternary potential

Abstract

It has been demonstrated that the synergistic effect of hydrogen (H) and helium (He) has a significant promoting effect on the nucleation antungstend growth of irradiation defects, leading to severe deterioration of material performance. In order to explore the synergistic evolution behaviors of H and He with irradiation defects in iron (Fe), we have developed a new Fe-H-He ternary potential through systematic fitting and optimization. During the processes, the interaction between H and He with vacancies and interstitial defects is given prominent consideration. Based on the present potential, we further explored the cooperative evolution behaviors of H-He-void complexes. On the one hand, it is clearly observed that both H and He perfectly form a typical core-shell structure in nanovoids with He inside and H outside, which is consistent with experimental observation. The number of H atoms trapped by He-void complexes will decrease with the increasing of He/V ratios, which is due to the repulsion between H and He. On the other hand, the presence of He-void complexes has a significant promoting effect on the formation of H platelets in Fe. The stress field generated by He-void complexes facilitates the aggregation and initial formation of H platelets, and its range expands as H aggregates, ultimately resulting in the formation of H platelets. The high H concentrations are required to form H platelets at high temperature. More importantly, the formation of H platelets can induce a transition in the local Fe lattice from body-centered cubic to face-centered cubic, indicating a substantial impact on the microstructure and properties of Fe. Consequently, the new Fe-H-He potential provides a powerful tool for exploring the synergistic evolution of H-He-defects and evaluating the performance of Fe in fusion devices.