A molecular dynamics study on the influence of vacancies and interstitial helium on mechanical properties of tungsten

Tungsten is a prime candidate material for use in plasma facing components in nuclear fusion reactors. This would entail weathering extreme conditions, such as high thermal loads and particle bombardment. It is of vital importance to understand how tungsten mechanically responds to these conditions, and how it is impacted by the defects that form. The current communication considers how the mechanical properties of tungsten are affected by the presence of several nanosized lattice defects: interstitial helium (both scattered throughout the sample and centrally clustered), isolated vacancies and vacancy clusters. All defects were found to lower the yield stress of the crystal, with vacancies and vacancy clusters having negligible influence during the elastic phase. Interstitial helium formed clusters, leading to the displacement of tungsten atoms, and a lowered stiffness at high strains. These negative effects of interstitial helium — along with the decrease in yield stress — were found to be partially negated by the presence of vacancies.