Characterization of neutron-induced copper-enriched clusters in pressure vessel steel weld: an APFIM study

Embrittlement of pressure vessel steels is controlled by complex interactions between a large number of variables making purely empirical predictions unreliable. It is necessary to have an accurate description of the changes that occur in the microstructure during neutron irradiation. A detailed atom probe field ion microscope examination of the microstructure of a neutron-irradiated commercial A533B-type weld (3.5 × 1019 n cm−2 (E > 1 MeV) at 283°C) is reported in this study. The plane-by-plane type analysis provides an accurate description of the neutron-induced copper-enriched clusters. The size, the morphology, the spatial distribution of solutes and the chemical composition of these features are determined. The matrix chemistry of this irradiated material was determined and compared with the as-fabricated weld and weld material that had been thermally aged for 93 000 h at 280°C. This comparison isolated the effect of neutron irradiation from any thermally induced microstructural evolution.