Dislocation Pinning in Helium-Implanted Tungsten: A Molecular Dynamics Study

TL;DR

This study uses molecular dynamics to analyze how helium-implantation-induced defects in tungsten interact with dislocations, revealing size-dependent pinning effects and defect-clearing mechanisms relevant to material hardening.

Contribution

It provides new insights into the atomic-scale interactions between helium clusters and dislocations in tungsten, linking molecular dynamics results with crystal plasticity models.

Findings

Helium clusters with 3-10 He2V-SIA form and increase pinning strength with size.

Dislocations bow around helium clusters and unpin by carrying SIAs, leaving helium-vacancy complexes.

Helium-induced solute hardening force is approximately 700 MPa, matching previous models.

Abstract

The interaction of edge dislocation with helium-implantation-induced defects in tungsten is investigated using molecular dynamics. Following prior investigations, we consider defects with two helium ions in a vacancy with a self-interstitial bound to it (He2V-SIA). Our observations suggest 3-10 He2V-SIA cluster together, with their pinning strength on glide dislocations increasing with size. For all cluster sizes, the dislocation bows around the cluster, until it gets unpinned, carrying the SIAs with it and leaving behind a helium-vacancy complex and newly created vacancies in its wake. The remnant helium-vacancy complex has little pinning effect, highlighting the defect-clearing process. A total solute hardening force for a distribution of clusters of different sizes, induced by 3000 appm of helium, is found to be approximately 700 MPa. This is in good agreement with the corresponding value of 750 MPa estimated in a previously developed crystal plasticity model simulating the deformation behaviour of the helium-implanted tungsten.