Nanomechanical testing of ODS steels irradiated with 1 MeV/amu heavy ions

Heavy ion beams with high damage production rate are widely used to evaluate radiation tolerance of promising nuclear reactor materials, such as oxide dispersion strengthened (ODS) alloys, including their mechanical properties. Since typical ion projected ranges do not exceed 1 micron, nanoindentation technique is the most convenient method for examination of irradiated materials. In present work we report data on radiation hardening of several ODS steels irradiated with 107 MeV Kr and 167 MeV Xe ions. Some samples were irradiated trough the special Al-foil filter in order to obtain the unfolding damage profile on the surface. The post-irradiation testing steels included conventional nanoindentation measurements and CSM for determination of possible size effects associated with indentation size effect as well as soft surface effect. Swift heavy ion induced changes in microstructure evolution were studied by transmission electron microscopy (TEM). It was found that hardening of the ODS steels irradiated with krypton and xenon ions of fission fragment energy for damage dose about 1 dpa level is in the range 5-25% (figure 1). TEM examination have revealed complete amorphization of carbide and (Y,Ti) oxide particles in ferritic matrices as a result of multiple amorphous latent track overlapping. At the same time no dissolution of nano-oxide particles was observed. This implies that radiation hardening is not due to changes in morphology of nanoparticles

Congruent patterns of genetic divergence revealed by allozymes and sequencing supports the existence of high levels of gene flow in a burrowing freshwater crab

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High-Energy Heavy Ion Tracks in Nanocrystalline Silicon Nitride

At present, silicon nitride is the only nitride ceramic in which latent ion tracks resulting from swift heavy ion irradiation have been observed. Data related to the effects of SHIs on the nanocrystalline form of Si3N4 are sparse. The size of grains is known to play a role in the formation of latent ion tracks and other defects that result from SHI irradiation. In this investigation, the effects of irradiation with high-energy heavy ions on nanocrystalline silicon nitride is studied, using transmission electron microscopy techniques. The results suggest that threshold electronic stopping power, Set, lies within the range 12.3 ± 0.8 keV/nm to 15.2 ± 1.0 keV/nm, based on measurements of track radii. We compared the results to findings for polycrystalline Si3N4 irradiated under similar conditions. Our findings suggest that the radiation stability of silicon nitride is independent of grain size

Helium in swift heavy ion irradiated ODS alloys

Combination of room temperature He ion implantation and swift heavy ion (SHI) irradiation in the multiple ion track overlapping regime has been used to study helium porosity in EP450 ODS steel containing crystalline or fully amorphous Y-Ti nano-oxides. It was found that helium bubbles formed during post-irradiation annealing have much better adhesion to amorphized precipitates in comparison with crystalline ones. However, this does not affect the overall porosity of the alloy which is defined by helium bubbles formed on structural defects inside the ferrite grain body and on grain boundaries. © 2019 Elsevier B.V.28th International Conference on Atomic Collisions in Solids (ICACS) / 10th International Symposium on Swift Heavy Ions in Matter (SHIM); Caen (France); Jul 01-07, 201