Enhanced irradiation tolerance of Fe30Cr25Ni20Co15Mn10 high-entropy alloy via nanotwin boundaries

Abstract

• There is no nanoscale precipitation and irradiation-induced hardening in Fe 30 Cr 25 Ni 20 Co 15 Mn 10 HEA at a high dose irradiation (∼ 70 dpa). • The HEA presents a very low swelling rate of ∼ 0.002%/dpa. • The RIS is observed for the first time at nanotwin boundaries in the HEA after irradiation. • The irradiation-induced segregation level is obviously suppressed in the HEA due to the sluggish atom diffusion. High-entropy alloys (HEAs) have been considered as a promising candidate for nuclear engineering due to their intriguing irradiation tolerance. The microstructure stabilities, including the radiation-induced precipitation (RIP), swelling, and segregation (RIS) in HEAs, are of great significance for applications. In this paper, the Fe 30 Cr 25 Ni 20 Co 15 Mn 10 HEA was irradiated by high-energy Au 2+ ions with a peak dose of ∼ 70 displacements per atom (dpa). The formation of voids, nanoscale precipitation, segregation, and mechanical properties before and after irradiation was characterized carefully, using scanning/transmission electron microscopy (S/TEM), atom probe tomography (APT), and nanoindentation. The results indicate that the HEA presents a very low swelling rate of ∼ 0.002%/dpa. After irradiation, no nanoscale precipitation is observed, confirming the excellent stability of the HEA microstructure. The RIS is observed for the first time at nanotwin boundaries in the HEA after irradiation. The elements, Co and Ni, are enriched slightly, while Fe, Cr, and Mn depleted on the nanotwin boundaries after irradiation. The irradiation-induced segregation level is obviously suppressed in the HEA due to the sluggish atom diffusion. The hardness remains almost unchanged after irradiation. The nanotwin boundaries act as defect sinks to absorb irradiation-induced vacancies and interstitials, reducing the swelling rate and relieving hardening. The low swelling, weak RIS level, and almost no hardening after a high dose irradiation indicate that the Fe 30 Cr 25 Ni 20 Co 15 Mn 10 HEA possesses an outstanding irradiation tolerance.