Diffusion mechanisms in fcc materials during irradiation with high energy particles due to vacancies, interstitials, di-interstitials, and dynamic crowdions are discussed. It is shown that in most alloys an increase in the degree of order is obtained by migrating vacancies and interstitials, and only in ∝-copper-zinc alloys mainly interstitials and in nickel-chromium alloys mainly vacancies are able to increase the degree of order during irradiation. The migration activation energies of interstitials and of vacancies for these two alloys are derived.
Mass transport also by channeling and by dynamic crowdions is shown for Ni63 in nickel irradiated with 1.85 MeV electrons.