Modeling injected interstitial effects on void swelling in self-ion irradiation experiments

Abstract

Heavy ion irradiations at high dose rates are often used to simulate slow and expensive neutron irradiation experiments. However, many differences in the resultant modes of damage arise due to unique aspects of heavy ion irradiation. One such difference was recently shown in pure iron to manifest itself as a double peak in void swelling, with both peaks located away from the region of peak displacement damage (DPA). In other cases involving a variety of ferritic alloys there is often only a single peak in swelling vs. depth that is located very near the ion-incident surface. We show that these behaviors arise due to a combination of two separate effects: 1) suppression of void swelling due to injected interstitials, and 2) preferential sinking of interstitials to the ion-incident surface, which are very sensitive to the irradiation temperature and atomic displacement rate. Care should therefore be used in collection and interpreting of data from the depth range outside the Bragg peak of ion irradiation experiments, as it is shown to be more complex than previously envisioned.

Radiation response of alloy T91 at damage levels up to 1000 peak dpa

“…The expansion of the void distribution from the front near-surface region to a deeper depth with increasing dose has been observed previously [32,36,37] and can be explained by the concept of defect imbalance [36,38]. This phenomenon combines the effects of forward scattering of the incoming ion and that of the injected interstitial effect, both of which are neutron-atypical phenomena arising in self-ion irradiation.…”

The effect of injected interstitials on void formation in self-ion irradiated nickel containing concentrated solid solution alloys

“…It has long been recognized that injected interstitials can suppress the swelling by recombining with vacancies. The source of extra interstitials varies but is mainly due to the injected ions during heavy ion irradiation [30][31][32][33][34]. The effect of injected interstitials can be seen clearly in the depth distribution of void number density and swelling, in Figure 4 and Figure 6, respectively.…”

Beam-contamination-induced compositional alteration and its neutron-atypical consequences in ion simulation of neutron-induced void swelling

“…However, voids were not observed to extend beyond this depth. A previous study has suggested that carbon atoms may alter the effective diffusivity of point defects, leading to dramatic changes in void swelling and void distribution [21]. If vacancy migration energy is slightly increased, void swelling shifts toward the surface.…”