Evolution of Irradiation-Induced Defect Landscape through Edge Dislocation and Vacancy Loop Interactions in Tungsten

Abstract

Structural materials in fusion reactors develop irradiation-induced defect populations that govern their mechanical behaviour. While advanced microscopy provides detailed characterisation of such defects, their dynamic evolution through dislocation-defect interactions during plastic deformation remains unresolved. Here, we address this gap using molecular dynamics simulations to resolve dislocation-defect interaction mechanisms and the resulting evolution of defect morphology and obstacle strength. Tungsten is the leading candidate plasma-facing material for fusion reactors, where vacancy loops are common irradiation defects. Using vacancy loops as a prototype defect, we systematically investigate their interactions with edge dislocations by varying loop size, orientation, and dislocation-loop intersection position. Parallel loops exhibit three distinct evolution pathways: complete annihilation, transformation into weaker remnant defects, or defect transport, depending on the intersection position and loop size. In contrast, inclined closed loops undergo dislocation reactions that produce sessile $⟨010⟩$ dislocation segments, leading to substantially higher obstacle strengths with little sensitivity to the intersection position. Repeated dislocation interactions further demonstrate that the defect landscape is not static: remnant defects can persist, transform, or lose their ability to impede subsequent dislocations, depending on the preceding interaction mechanism. These results show that the obstacle strength of a vacancy loop is governed not only by its initial size and orientation, but also by its interaction history and the resulting defect structure.