Abstract

For devices and materials used in radiation environments, such as wall materials and divertors of high energy accelerator target systems under high intensity beams and fusion reactors in close proximity to high temperature plasmas, it is important to evaluate the integrity of the materials so that they can withstand large amounts of radiation and high heat loads. In this study, we investigated the irradiation resistance of a tungsten-based material, one of the candidate materials for such an environment, by mechanical alloying and high-temperature hydrostatic sintering of a high-strength W material with a grain size of 1-2μm and dispersed small titanium or titanium oxide nanoparticles. This material was irradiated up to 0.66 dpa at 500 °C. The hardness change by nanoindentation and the microstructure and atomic arrangement by scanning transmission electron microscopy were examined. Normally, this irradiation condition is known to cause significant irradiation hardening, but it was found that no irradiation hardening occurred in this material. In addition, the crystal lattice images showed lattice (atomic arrangement) distortions of less than a nanometer, but no misfit dislocations were observed. These results suggest that the formation and growth of irradiation defect clusters was suppressed by the lattice distortion formed at the nano-level or below before irradiation, and that irradiation hardening was greatly suppressed.

Keywords: Tungsten; TiC; Ti; Titanium oxide; Irradiation; Irradiation damage; Nano-indentation; STEM; Irradiation hardening; Crystal lattice distortion