Molecular dynamics study of irradiation damage and helium effects in a simplified Fe-Ni-Cr alloy system: Relevant to alloy 800H

TP Kaloni and IC Njifon and E Torres, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 569, 165871 (2025).

DOI: 10.1016/j.nimb.2025.165871

Fe-Ni-Cr alloy 800H is a critical structural material in nuclear reactors. Under irradiation, it faces significant challenges due to defect formation and Helium (He) generation, which adversely affect its microstructure and durability. In this study, we conducted molecular dynamics simulations of the combined effects of He and irradiation in polycrystalline Fe-Ni-Cr alloy 800H. Our findings show that irradiation induces the transition of the polycrystals into a single crystal. However, increasing the number of grains and He concentration favored the polycrystalline state. We also observe a decrease in the number of dislocations and an increase in large defects with the increase of the He content. Our structural evaluations reveal that He clusters mainly accumulate at those large defects, which are surrounded by dislocation loops. The interplay between the formation of He clusters and irradiation damage results in substantially deteriorating the mechanical properties of Fe-Ni-Cr alloy 800H structures. Our simulations provide valuable insights into the degradation mechanisms under the combined effects of He and irradiation damage.

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