The displacement damage produced in metals by high energy particles such as electrons, protons, ions, or neutrons can result in significantly different defect distributions. Typically, collisions with light particles such as electrons produce Frenkel pairs, i.e., pairs of spatially separated self-interstitials and vacancies. In contrast, particles such as heavy ions or neutrons create collision cascades which yield not only Frenkel pairs but also interstitial and vacancy clusters resulting in a heterogeneous defect distribution. Depending on temperature, point defects produced during irradiation can migrate and either recombine or agglomerate to form larger defect clusters that can affect the microstructure of the material. On the other hand, high levels of He are produced by transmutation under neutron irradiation conditions. This element strongly interacts with vacancies produced during irradiation and agglomerates into stable He-vacancy clusters that can deteriorate mechanical properties of the material. In the present investigation we studied the evolution of defects and the formation of He-vacancy clusters in irradiated Fe using Rate Theory (RT) and kinetic Monte Carlo (kMC) approaches. After describing kMC and RT formalisms, we will compare kMC and RT results obtained for an isochronal annealing of defects created by displacement cascades in Fe. In the second part, a RT model for the agglomeration of He and vacancies in Fe will be presented and results will be compared to experimental desorption data. In particular, we will show how impurities like carbon can affect the clustering of He.
Universidad de Alicante