TEM investigation of neutron irradiated and post irradiation annealed tungsten materials

In this paper, we present a transmission electron microscopy study of three tungsten grades subjected to neutron irradiation and post-irradiation annealing. The irradiation was performed at 600 .C up to 0.2 dpa and the microstructure was investigated after the irradiation, reported in a previous publication, as well as after the annealing at 800 .C and 1000 .C. The evolution of the radiation induced defects is characterized and the overall microstructural features are compared in three states: virgin-as irradiated – as annealed after irradiation. The annealing at 800 .C causes an increase in the loop and void densities and moderate increase in the mean sizes. An increase of the annealing temperature to 1000 .C causes a reduction of the loop density, while the loop size increases. Also the void density reduces, but not necessarily the void fraction. The peak of the void volume fraction is found around 800 .C, which coincides with the earlier reported experimental data on the void swelling peak under neutron irradiation.