Dislocation pinning in helium-implanted tungsten: A molecular dynamics study

Using molecular dynamics simulations, we investigate the interaction of edge dislocations with He-filled Frenkel pairs (He2V-SIA), the predominant defect type in helium-implanted tungsten. Clusters of 3-10 He2V-SIA are seen to be stable with their pinning strength increasing with size. For all cluster sizes, the dislocation bows around the cluster and unpins while carrying SIAs with it. The helium-vacancy complex and new vacancies left behind, have little pinning effect, explaining the "defect-clearing" and experimentally observed deformation softening. The predicted solute hardening for 3000 appm helium-induced defect distribution of varying sizes, is in excellent agreement with previous experimental observations.