Effect of dose rate on the characteristics of dislocation loops in palladium: In-situ TEM analysis during 30 keV H 2+irradiation

Ion irradiation is usually used to simulate neutron irradiation to accelerate the evaluation of the irradia-tion behavior of reactor materials. However, the validity of using a high damage rate of ion irradiation to simulate a low damage rate of neutron irradiation has always been a controversial topic. Here, the effect of two dose rates (2.94 x 10 -6 and 7.35 x 10 -5 dpa s -1 ) on the characteristics and evolution of dislo-cation loops in palladium was studied in situ during 30 keV H 2 + irradiation using transmission electron microscopy. The dose rate obviously affected the nucleation rate and growth rate of dislocation loops, the types (Frank loops or perfect loops) of dislocation loops, and the irradiation hardening and total damage obtained from the product of average loop size and loop density. At the same irradiation dose, a high dose rate would lead to high loop density, small average loop size, low loop growth rate, and low irra-diation hardening and damage induced by loops in pure Pd. Meanwhile, it was found for the first time that a high dose rate was beneficial to the generation of perfect dislocation loops. The effect of dose rate was attributed to the different dynamic equilibrium results between the effective generation rate of point defects and their absorption rate by existing sinks. The present results show that the effect of dose rate should be considered when using ion irradiation to simulate neutron irradiation to evaluate the irradiation damage to materials.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

In this study, the effect of two dose rates on the characteristics and evolution of dislocation loops in palladium during 30 keV H2+ irradiation was investigated using transmission electron microscopy. The dose rate significantly influenced the nucleation and growth rates, types, irradiation hardening, and total damage of dislocation loops. It was found that a high dose rate resulted in high loop density, small average loop size, low loop growth rate, and low irradiation hardening. Additionally, high dose rate promoted the formation of perfect dislocation loops.