In-situ TEM characterization of dislocation loops in tungsten under simultaneous helium and hydrogen irradiation

Abstract

The interaction among He, H, and irradiation-induced dislocation loops in pure tungsten was examined through 30 keV simultaneous He+ and H2+ irradiation at 1073 K. Three different He/H concentration ratios (0.1, 1, and 5) were utilized. This study involved the characterization of the number density, average size, and size distribution of loops by varying the dose percentage of He and H. Increasing the dose percentage of He facilitated the loop nucleation. Increasing the total irradiation dose not only increased loop nucleation sites but also changed the loop size distribution from unimodal to bimodal. The specific Burgers vectors and habit planes of loops were carefully determined using the inside-outside method in combination with the g·b invisibility criterion and crystallographic map. The proportion of interstitial 1/2<111> loops exceeded 95 %, in which four Burgers vector variants of 1/2[111], 1/2[1¯11], 1/2[1¯1¯1], and 1/2[11¯1] were identified. Increasing the dose percentage of He led to an even distribution of Burgers vector variants. The {110} habit planes were found to deviate at an angle of 35° from the {111} ones. A majority of {111} habit planes were found compared to {110} for 1/2<111> loops. Altering the dose percentage of He or H showed no apparent effect on the habit planes of {111} or {110} for 1/2<111>loops, nor did it affect their average size when situated on {111} or {110}.