In-situ TEM study of the effect of hydrogen-helium ratio on defect characteristics in Fe9Cr1.5W0.4Si F/M steel during H2+ & He+ simultaneous irradiation

Abstract

The effect of hydrogen and helium interaction, especially H–He ratio, on the irradiation behavior of nuclear materials has not yet been resolved. However, this is an important basis for evaluating the irradiation properties of nuclear materials and developing high irradiation resistant materials. Here, 30 keV H2+ and He+ dual beams with four H–He ratios of 0:10, 3:10, 15:10, and 30:10 were used to irradiate the newly developed Fe9Cr1.5W0.4Si F/M steel in TEM to in-situ study the interaction and ratio effect of hydrogen and helium. The addition of H atoms significantly promoted the nucleation of dislocation loops and bubbles. In the early stage of irradiation, the average size and density of dislocation loops increased with the increase of H–He ratio. Meanwhile, the larger the H–He ratio, the easier it was to form a complex dislocation network. Furthermore, the final saturation size of bubbles increased with the increase of H–He ratio. It was first found that the swelling was affected by H concentrations, with high H concentrations slowing down the increase in swelling. For a certain irradiation dose, a specific H–He ratio would lead to a swelling peak of Fe9Cr1.5W0.4Si F/M steel. The super-sized bubbles at grain boundaries (GBs) were found after H addition, resulting in a bigger swelling of GBs than the matrix. Both the swelling of the GBs and the matrix show a dependence on the H–He ratio. The current work is of great significance for understanding the interaction between hydrogen and helium in nuclear materials.