In situ studies on the evolution of damage microstructures in tungsten under heavy ion irradiation and post annealing

The evolution of heavy-ion irradiation induced microstructures, followed by annealing experiments, was analyzed in situ and characterized systematically in tungsten via transmission electron microscopy. The formation and evolution of loop rafts, dislocation decoration, and tangled dislocation networks were analyzed during irradiation. Consisting of 1/2<111> loops, raft structures had a preferred orientation, which was dependent on loop geometry. Decoration of a near-edge line dislocation with loops led the line first to curve and then annihilate. Drastic loss of loops, loop-loop coalescence, glide of jogged line dislocations as well as untangling of dislocation networks were observed during post-annealing. The gliding of glissile loops varied with its size, while the motion of line dislocations depended on their nature. The glide distance for the small loops with a size range from 1 to 3 nm was 6 times larger than the large loops with a size range from 5 to 8 nm. A near-edge dislocation had the largest mobility, a near-screw one had the lowest mobility, and a mixed one had the mobility in between. The direct observation and comprehensive analysis of the complicated interaction among dislocations will offer insights into the bridge between the microstructural evolution and macroscopic response to irradiation damages.