Diffusion-mediated chemical concentration variation and void evolution in ion-irradiated NiCoFeCr high-entropy alloy

• Published in: Journal of materials research Vol. 36
• Main Authors: Fan, Zhe, Zhong, Weicheng, Jin, Ke, Bei, Hongbin, Osetskiy, Yury N., Zhang, Yanwen
• Format: Journal Article
• Language: English
• Published: United States Materials Research Society 04-02-2021
• Subjects: chemical concentration; defect migration; GENERAL STUDIES OF NUCLEAR REACTORS; high-entropy alloys; MATERIALS SCIENCE; preferential diffusion; void swelling
• ISSN: 0884-2914; 2044-5326

High-entropy alloys (HEAs) are proposed as potential structural materials for advanced nuclear systems, but little is known about the response of matrix chemistry in HEAs upon irradiation. Here, we reveal a substantial change of matrix chemical concentration as a function of irradiation damage (depth) in equiatomic NiCoFeCr HEA irradiated by 3 MeV Ni ions. After ion irradiation, the matrix contains more Fe/Cr in depth shallower than ~900–1000 nm but more Ni/Co from ~900–1000 nm to the end of the ion-damaged region due to the preferential diffusion of vacancies through Fe/Cr. Preferential diffusion also facilitates migration of vacancies from high radiation damage region to low radiation damage region, leading to no void formation below ~900–1000 nm and void formation around the end of the ion-damaged region at a fluence of 5 × 1016 cm-2 (~123 dpa, displacements per atom, peak dose under full cascade mode). As voids grow significantly at an increased fluence (8 × 1016 cm-2, 196 dpa), the matrix concentration does not change dramatically due to new voids formed below ~900–1000 nm.