Kinetic of solute clustering in neutron irradiated ferritic model alloys and a French pressure vessel steel investigated by atom probe tomography

The embrittlement of reactor pressure vessel steels under neutron irradiation is partly due to the formation of solute clusters. To gain more insight into their formation mechanisms, ferritic model alloys (low copper Fe-0.08 at.% Cu, Fe-0.09 Cu-1.1 Mn-0.7 Ni (at.%), and a copper free Fe-1.1 Mn-0.7 Ni (at.%)) and a French 16MND5 reactor pressure vessel steel, were irradiated in a test reactor at two fluxes of 0.15 and 9 x 10(17) n(E> 1 MeV) m(-2) s(-1) and at increasing doses from 0.18 to 1.3 x 10(24) n(E> 1 MeV) m(-2). Atom probe tomography analyses revealed that nanometer-size solute clusters were formed during irradiation in all the materials, even in the copper free Fe-1.1 Mn-0.7 Ni (at.%) alloy. It should be noted that solute segregation in a low-Ni ferritic material was never reported before in absence of the highly insoluble copper impurity. The manganese and nickel segregation is suggested to result from a radiation-induced mechanism. (C) 2009 Elsevier B.V. All rights reserved.