In-situ TEM analysis on early-stage evolution of dislocation loops in 30 keV H2+ irradiated W

Abstract

The evolution and dynamic behaviors of dislocation loops in tungsten (W) under 30 keV H2+ irradiation have been studied through in-situ TEM observation. The study covered a dose range of ∼0.01–0.09 dpa at irradiation temperatures of room temperature (RT), 723 K, and 973 K. A large density of dot-like defect clusters governed at RT, and defect clusters evidently grew up accompanying with an obvious drop of loop population at higher temperatures. A detailed characterization on geometry, crystallographic information, and fraction of loop variants with different Burgers vectors was carried out in two distinct regions of different thickness within one grain. Loops were determined as 1/2<111>-type at ∼0.09 dpa for 723 K, and a mixture of 1/2<111> and <100> loops was found at ∼0.03 dpa for 973 K. An increasing temperature gave rise to a significant loss of 1/2<111> loops towards absorption sinks, and it facilitated the formation of <100> loops. Wavy morphology of a 1/2<111> loop produced from loop-loop coalescence was observed at 723 K. Transformation from a 1/2<111> to a <100> loop without coalescing with other loops was found at 973 K. A comparison between the estimated hardness increase contributed from dislocation loops based on the hardening model and experimental measurements from neutron irradiated bulk W was carried out.