Impact of helium irradiation on the crystallographic orientation change in single-crystalline tungsten * *This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish

Abstract

Understanding the helium effects on the surface modifications of tungsten is of great interest and significance for developing plasma-facing materials. Our recent studies revealed that the ion irradiation of helium at room temperature produces 〈111〉-oriented surface grains in single-crystalline tungsten {100} and {110}, which may play an important role in the surface and subsurface evolutions of tungsten subjected to fusion-relevant service environments. Although the driving force for the formation of surface grains is well explained by ion channeling effect, the underlying formation mechanism remains unclear. In this work, we investigated the orientation relationship between irradiation-induced new surface grains and single-crystalline tungsten matrix. The experimental results of electron backscatter diffraction demonstrated that the formation of most 〈111〉-oriented surface grains in both helium-irradiated tungsten {100} or {110} can be regarded as the grain rotation of matrix around its in-plane 〈110〉 axis.