Inversion of dislocation loop nature driven by cluster migration in self-ion irradiated nickel

Nickel is widely used as a fcc model material to obtain insight into fundamental mechanisms of radiation damage. This work presents irradiation of high-purity nickel using self-ions at 450 °C and fine analysis of dislocation loops in specimens prepared by Focus Ion Beam using Transmission Electron Microscopy. For the first time to our knowledge, an inversion of loop nature (vacancy-type in irradiated zones v.s. interstitial-type in unirradiated zones) and a change of loop Burgers vector (1/3<111> and 1/2<110> loops v.s. only 1/2<110> loops) is identified along the implantation direction in irradiated nickel. This change may be attributed to the formation of interstitial 〈110〉 crowdions and their long-range one-dimension migration. A defect-free layer related to the annihilation of vacancy defects by injected atoms is detected. . It allows the identification of the injection peak which is uncommon for self-ion irradiated specimens and validates the damage calculations.