The influence of different isochronal annealing temperature on helium ion irradiation damage of W-Nb composites

Abstract Considering that the plasma-facing materials (PFMs) would be affected by helium ion irradiation, the influence of isochronal annealing at different temperatures on the irradiation damage of W-Nb composites was studied in this work. The microstructure changes of W-Nb composite with ball-milling time of 25 and 36 h before and after isochronal annealing at different temperatures were characterized by scanning electron microscopy or transmission electron microscopy. After helium ion irradiation, only the surface of the W-rich regions in the W-Nb composite after ball milling for 36 h had the same fuzz structure as pure W. During the subsequent heat treatment, the density of the fuzz structure on the surface of pure W increased at 900 °C, and gradually decreased with the increase of temperature until it disappears. The composites that underwent ball-milling for 25 and 36 h had the same surface morphology changes. More helium bubbles migrated to the surface of the W-rich regions in the composites at 900 °C. When the temperature rose to 1300 °C, the grain growth occurred in the Nb-rich regions. Notably, the density of fuzz structure in the W-rich regions did not increase significantly during the whole heat treatment process, which might be caused by the increase of helium desorption temperature in the W-Nb composite due to the addition of Nb.