Modeling the helium transport and premature intergranular fracture by dislocation motion in irradiated metals

Abstract

Helium migration is an important mechanism of helium embrittlement in irradiated metallic materials, which can severely affect their service reliability. Despite many efforts to reveal the mechanism of helium migration during plastic deformation, a mechanistic understanding of helium transport through dislocation motion is still lacking. In this work, we developed a theoretical model within the coupled framework of crystal plasticity and helium diffusion, to account for the helium transport due to the bidirectional dislocation motion. Our simulation results show that, for austenitic stainless steel, such motion has a significant impact on helium migration, leading to an enriched helium concentration on the grain boundaries (GBs), and thus resulting in a higher risk of intergranular fracture. Besides, our results also indicate that temperature and irradiation defect affect the helium concentration on the GBs by regulating the intragranular helium distribution. The present study reveals the key role of dislocation motion in regulating helium migration, a firm step toward a more comprehensive understanding over the failure mechanisms of irradiated metallic material.