The micro-mechanical properties of ion irradiated tungsten

Abstract

Micro-mechanical testing techniques have proved successful in extracting the properties of bulk materials from small-scale tests. In particular, focussed ion beam (FIB)-machined micro-cantilevers have been shown to produce quantitative, accurate modulus values when used on materials such as pure copper or silicon. In this work, this technique is extended to study the micro-mechanical properties of ion-irradiated, commercially pure tungsten. Ion irradiation has been used to model the cascade damage produced by fusion neutrons in tungsten. Due to the small depth of ion-implanted layers, micro-mechanical tests must be carried out to determine the mechanical properties of the material. These cantilever tests and additional nanoindentation produces data comparable with literature data. An increase in hardness after implantation is measured, while the yield stress of the material remains unchanged. Helium implantation has an effect on the mechanical properties of tungsten. It is hypothesized that this is due to a change in the damage formed under irradiation, from dislocation loops formed in self-ion irradiation to helium-filled vacancies in simultaneous irradiation.