TEM studies of 1 MeV Fe⁺ ion-irradiated W alloys by wet chemical method: High-temperature annealing and deuterium retention

In this study, the microstructural changes in irradiated W-1 wt%Pr₂O₃, W-1 wt%La₂O₃, W-1 wt%TiC and W-1 wt%ZrC specimens by 1 MeV Fe⁺ ion irradiation to doses of 1 dpa at room temperature have been characterized by transmission electron microscopy (TEM) to understand the radiation damage. The specimens of 1 dpa were consecutively annealed at temperatures of 600 °C, 800 °C, 900 °C and 1100 °C for 1 h, and the post-irradiation annealing effect on the microstructure was studied. Microstructural features such as dislocations, dislocation loops and dense dislocation networks were observed by the means of TEM. There was a significant change in the microstructure of the tungsten (W) after irradiation and post-irradiation annealing. W-1 wt%TiC likely consisted of fewer radiation-induced defects and hence exhibits higher resistance to radiation-induced microstructural changes than the others. The general trend is that the density of defect clusters decreases while the average size of the clusters increases with the annealing temperature. A complete removal of dislocation structures at 1100 °C occurred in all materials. The irradiation damage effect of Fe⁺ ions on the deuterium retention of as-synthesized W-based composites was investigated. Thermal desorption spectroscopy of W implanted with ions was performed using the low-energy ion irradiation system of Kyoto University. Compared with the samples without Fe⁺ pre-irradiation, the deuterium retention of the four composites increased after Fe⁺ pre-irradiation. The retained amount of deuterium was also increased with the increase in the Fe⁺ irradiation dose. This is of vital importance to the scientific community working on these materials for extreme irradiating environments.