Nanoindentation yield load reduction in tungsten caused by hydrogen ion irradiation near the threshold displacement energy

Abstract

Threshold displacement energy (TDE) is a central parameter describing radiation damage, representing the energy required to create a stable point defect. Recent modelling has mapped a substantial variation of tungsten TDE with crystallographic direction which may have important materials engineering implications. Here, polycrystalline recrystallized tungsten is exposed to hydrogen irradiation in the energy range of 500–800 eV, expected to impart energy near the TDE. Nanoindentation is used to probe mechanical properties, particularly yield load. We find yielding occurring at significantly reduced yield load following 800 eV irradiation versus 600 eV. Despite sampling grains with predicted high TDE, no correlation between yield load reduction and predicted TDE is observed. This work demonstrates a distinct evolution of tungsten plasticity due to proton irradiation in the 600–800 eV range consistent with displacement damage production at a TDE of 40 eV, and the sensitivity of nanoindentation to probe near-threshold radiation damage.