Mitigated fuzz growth and uneven elemental distribution in tungsten-based high-entropy alloys exposed to helium plasma

The potential of tungsten (W)-based high-entropy alloys (HEAs) as plasma-facing materials (PFMs) for future fusion reactors has been evaluated through an investigation of fuzz growth. W-based HEAs (WTaCrV, WTaCrVTi) and pure W fabricated via mechanical alloying and high-pressure sintering have been exposed to helium (He) plasma at 1073 K with an ion energy of 60 eV. After He plasma exposure, all samples exhibit fuzz nanostructures. Detailed analyses of fuzz length, He bubble size, and elemental distribution within the fuzz nanostructures are conducted. The two W-based HEAs demonstrate distinct advantages, exhibiting fuzz lengths reduced by 37.1% (WTaCrV) and 34.3% (WTaCrVTi), alongside smaller He bubble sizes compared to pure W. However, no significant differences in fuzz length or He bubble size are observed between WTaCrV and WTaCrVTi. Significantly, scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM-EDS) analysis reveals that the fuzz nanostructures predominantly comprise W and Ta, attributed to the preferential nucleation and growth of He bubbles in regions enriched with these elements. These findings provide critical insights into the underlying mechanisms governing fuzz formation in W-based HEAs. The superior resistance to fuzz growth in these W-based HEAs guides the design and development of PFMs in future fusion reactors.