In-situ TEM investigation of dislocation loop reaction and irradiation hardening in H_(2)^(+)-He^(+) dual-beam irradiated Mo

Through in-situ TEM observation during 30 keV H_(2)^(+)-He^(+) dual-beam irradiation at 723 K,the reaction and transformation of dislocation loops in pure Mo were investigated,especially for<100>loops.Irradiation could directly cause the formation of 1/2<111>loops and<100>loops,but 1/2<111>loops were dominant.In-situ observation confirmed the formation mechanism of<100>loops,including direct irradiation induced mechanism,1/2<111>loop direct conversion mechanism,and reaction mechanism of two 1/2<111>loops.Meanwhile,the reaction of two 1/2<111>loops to produce<100>loop should not require the strict size similarity condition.The reaction between 1/2<111>loops could also produce 1/2<111>loop,which was essentially a process in which one loop absorbed another one.The yield strength increment caused by irradiation-induced loops was analyzed,and its saturation value reached0.48 GPa at 0.06 dpa.Compared with single He+irradiation,the number density and average diameter of loops increased significantly and more serious damage was caused under the synergistic effect of hydrogen and helium.The mechanism based on in-situ experimental observation was discussed in depth.