High He-ion irradiation resistance of CrMnFeCoNi high-entropy alloy revealed by comparison study with Ni and 304SS

High entropy alloys (HEAs) have presented potential applications in nuclear power plants owing to their novel atomic structure based high irradiation resistance. However, understanding of He-ion irradiation of HEAs is still lacking. In this work, we reveal He-ion irradiation resistance of HEA CrMnFeCoNi by comparison study with a pure Ni and a 304 stainless steel (304SS). It is found that the damage structure in the three materials can be characterized with He bubbles and stacking faults/stacking fault tetrahedrons ((SFs/SFTs), which show a similar depth distribution after He-ion irradiation at both RT and 450 degrees C. Although the He bubbles have a similar size about 2 nm after irradiation at RT, the He bubble sizes of the HEA, 304SS, and Ni increase to 4.0 +/- 0.9, 5.3 +/- 1.0 and 6.7 +/- 1.0 nm after irradiation at 450 degrees C, respectively. Moreover, the density of SFs/SFTs displays in an order of Ni < 304SS < HEA at both RT and 450 degrees C. The He-ion irradiation at RT causes significant hardness enhancement for the three materials, however, compared to RT, after irradiation at 450 degrees C, the Ni presents softening, while the 304SS, especially the HEA, shows further hardening. Thus, the HEA CrMnFeCoNi possesses the smallest He bubble size, the densest SFs/SFTs, and the highest hardening, indicating the best structural stability, as well as the best He-ion irradiation resistance, which can be attributed to its low mobility of He atoms and point defects. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.