Evaluation of Radiation Response in CoCrFeCuNi High-Entropy Alloys.

CoCrFeCuNi high-entropy alloys (HEAs) prepared by arc melting were irradiated with a 100 keV He ⁺ ion beam. Volume swelling and hardening induced by irradiation were evaluated. When the dose reached 5.0 × 10 ¹⁷ ions/cm ² , the Cu-rich phases exhibited more severe volume swelling compared with the matrix phases. This result indicated that the Cu-rich phases were favorable sites for the nucleation and gathering of He bubbles. X-ray diffraction indicated that all diffraction peak intensities decreased regularly. This reduction suggested loosening of the irradiated layer, thereby reducing crystallinity, under He ⁺ ion irradiation. The Nix-Gao model was used to fit the measured hardness in order to obtain a hardness value H ₀ that excludes the indentation size effect. At ion doses of 2.5 × 10 ¹⁷ ions/cm ² and 5.0 × 10 ¹⁷ ions/cm ² , the HEAs showed obvious hardening, which could be attributed to the formation of large amounts of irradiation defects. At the ion dose of 1.0 × 10 ¹⁸ ions/cm ² , hardening was reduced, owing to the exfoliation of the original irradiation layer, combined with recovery induced by long-term thermal spike. This study is important to explore the potential uses of HEAs under extreme irradiation conditions.