In-situ transmission electron microscopy observation of the evolution of dislocation loops and gas bubbles in tungsten during H2+ and He+ dual-beam irradiation

Dislocation loop and gas bubble evolution in tungsten were in-situ investigated under 30 keV H2+ and He+ dual-beam irradiation at 973 K and 1173 K. The average size and number density of dislocation loops and gas bubbles were obtained as a function of irradiation dose. The quantitative calculation and analysis of the migration distance of 1/2  $$\langle{111}\rangle$$  loops at low irradiation dose indicated that the main mechanism of the formation of  $$\langle{100}\rangle$$  loops should be attributed to the high-density helium cluster inducement mechanism, instead of the 1/2  $$\langle{111}\rangle$$  loop reaction mechanism. H2+ and He+ dual-beam irradiation induced the formation of  $$\langle{100}\rangle$$  loops and 1/2  $$\langle{111}\rangle$$  loops, while increasing the irradiation temperature would increase  $$\langle{100}\rangle$$  loop percentage. The percentage of  $$\langle{100}\rangle$$  loops was approximately 18.6% at 973 K and increased to 22.9% at 1173 K. The loop reaction between two 1/2  $$\langle{111}\rangle$$  loops to form a large-sized 1/2  $$\langle{111}\rangle$$  loop was in-situ observed, which induced not only the decrease of the number of 1/2  $$\langle{111}\rangle$$  loops but also the significant increase of their sizes. The  $$\langle{100}\rangle$$  loops impeded the movement of dislocation line and tended to escape from it instead of being absorbed. With the increase of irradiation dose, the yield strength increment ( $$\Delta {\sigma }_{\mathrm{l}\mathrm{o}\mathrm{o}\mathrm{p}}$$ ) caused by the change of loop size and density increased first and then decreased slightly, while the yield strength increment ( $$\Delta {\sigma }_{\mathrm{b}\mathrm{u}\mathrm{b}\mathrm{b}\mathrm{l}\mathrm{e}}$$ ) caused by the change of bubble size and density always increased. Meanwhile, within the current irradiation dose range, $$\Delta {\sigma }_{\mathrm{l}\mathrm{o}\mathrm{o}\mathrm{p}}$$ was much larger than $$\Delta {\sigma }_{\mathrm{b}\mathrm{u}\mathrm{b}\mathrm{b}\mathrm{l}\mathrm{e}}$$ .