Defect distribution in ion-irradiated pure tungsten at different temperatures

Tungsten (W) has been selected as the armor materials for divertor in fusion reactors. To investigate the temperature dependent microstructural evolution under fusion relevant environment, pure W was irradiated with dual beam of 6.4 MeV Fe3+ and 1 MeV energy degraded He+ at 300 °C, 500 °C, 700 °C and 1000 °C. The overall distribution of microstructures were observed. At 300 °C, a high dislocation density zone (HDDZ) appeared at the end of radiation area. The HDDZ gradually disappeared with increasing irradiation temperature, instead, a low dislocation density zone (LDDZ) appeared between the front zone (FZ) and diffusion zone (DZ). At all the irradiation temperatures, both dislocation lines and loops were observed, while bubbles were observed only at 500 °C and above. Loop rafts appeared in the whole irradiated area from 300 °C to 700 °C, but only in the defect diffusion zone (DZ) at 1000 °C. Dislocation loop denuded zone was formed along grain boundaries, suggesting that grain boundaries suppress the formation of dislocation loops. Bubbles at grain boundaries tended to have a larger size than those in the matrix, indicating that bubble growth was accelerated in grain boundaries.