Structural damage and phase stability of cobalt-free FeCrNi medium-entropy alloy under high-fluence ion irradiation

• Published in: Applied surface science 2024-06, Vol.657, p.159669, Article 159669
• Main Authors: Fu, Ao, Liu, Bin, Tan, Fusheng, Cao, Yuankui, Li, Jia, Liu, Bo, Fang, Qihong, Liaw, Peter K., Liu, Yong
• Format: Article
• Language: English
• Subjects: Ion irradiation; Medium-entropy alloy; Microstructure; Molecular dynamics simulation; Powder metallurgy; Radiation damage
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2024.159669

[Display omitted] •A cobalt-free fcc FeCrNi MEA was manufactured by powder metallurgy method.•The alloy maintains high structural stability even at a high irradiation fluence of 5 × 1016 Au ions/cm2.•The alloy shows excellent irradiation-hardening resistance.•Microstructural evolution under high-fluence irradiation was revealed by molecular dynamics simulation. A cobalt-free FeCrNi MEA was successfully synthesized and irradiated with 7.5 MeV Au ions at room temperature over a wide fluence from 5 × 1015 to 5 × 1016 Au ions/cm2. Microstructural characterization shows that the FeCrNi MEA exhibits low structural damage and high phase stability under high-fluence ion irradiation, and diffuse dislocations and defect clusters, especially dislocation loops and stacking-faults (SFs), are the main microstructural feature after irradiation. Limited elemental segregation at grain-boundaries and nanoscale Au clusters can be observed only in the specimen irradiated at the highest fluence. Meanwhile, void formation and phase instability are absent in any irradiation condition. Cascade-collision simulation reveals that large-size vacancy cluster collapses into the stacking fault tetrahedrons (SFTs) and abundant dislocation structures, especially the high-fraction movable Shockley dislocations at the high-energy ion irradiation, contributing to the absence of voids and the easily activated dislocation networks. Owing to these microstructural features, the irradiated specimens only exhibit a slight hardness increase (26 % at 210 dpa), indicating a superior resistance to irradiation hardening. Overall, this work supports that the FeCrNi MEA possesses an outstanding irradiation tolerance especially under high-fluence ion irradiation, thereby having good application prospects in the field of advanced nuclear reactors.