Heterogeneous irradiation-induced copper precipitation in ferritic iron–copper model alloys

The mechanism at the origin of the formation of nano-copper-enriched clusters in the ferritic matrix of nuclear reactor pressure vessel steel is not yet fully understood. In this work, specific irradiation experiments were carried out using 3 MeV electron and 150 keV Fe+ ions in order to point out the effect of (i) free migrating point defects (produced as Frenkel pairs with 3 MeV electron) and (ii) the ballistic mixing and partial recombination of atoms due to displacement cascades (produced with ions). In both cases the irradiation-induced phase transformation were characterized using the 3D atom probe technique. The time-dependant evolution of the point defect population was computed using the cluster dynamic code (MFPVIC) developed at CEA. The combination of experiment and simulation shows that, in low copper (<0.1 at.% Cu) FeCu alloys, heterogeneous irradiation-induced copper precipitation is taking place on point defects clusters generated by 20–30 keV displacement cascades.