Experimental study and modelling of copper precipitation under electron irradiation in dilute FeCu binary alloys

In order to study the effect of the supersaturation of freely migrating defects on the precipitation of copper in high residual copper pressure vessel steels under neutron irradiation, FeCu (1.34, 0.30 and 0.11 at.% Cu) model alloys were irradiated between 175 and 360°C with high energy electrons. On-line electrical resistivity measurements and small angle neutron scattering (SANS) under magnetic field experiments were carried out. The use of the latter method to get the chemical composition of the precipitates is discussed. We show that the mechanisms of precipitation are identical under electron irradiation and under thermal aging. The sole effect of electron irradiation on the precipitation is to enhance the kinetics. A modelling of copper precipitation based on cluster dynamics is proposed. A comparison between our SANS results obtained under electron irradiation and those under neutron irradiation published in the literature shows that the mechanisms of precipitation are very likely different with both kinds of particles.