Three Dimensional Atom Probe Observations of Reactor Pressure Vessel Model Alloys Irradiated by Neutrons and Heavy Ions

Microstructural characterization of reactor pressure vessel mode alloys irradiated by neutrons and Fe ions was performed using three dimensional atom probe tomography. Ultra fine clusters of solute atoms, such as Cu, Ni, Mn and Si, with diameter in the range of 2-3 nm were formed at high number density in all the alloys. The cluster number density and the mean diameter of the alloys irradiated by Fe ion were higher and smaller, respectively, than those of neutron irradiated alloys. The clusters in Fe ion irradiated alloys had less Cu and more Ni and Si content than those of neutron irradiated alloys. The increase in hardness of both irradiated alloys had almost linear correlation with the square root of the volume fraction of solute atom clusters.