Abstract
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.
Highlights
High-entropy alloys (HEAs) have attracted significant research interests due to their excellent strength, ductility, and radiation resistance [1, 2, 3, 4, 5, 6]
Fan et al [22] showed that void growth can be suppressed at relatively low doses, substantial void growth can occur after an incubation dose of ∼123 dpa under full cascade mode in NiCoFeCr irradiated by 3 MeV Ni-ion irradiation at 500 °C
A previous work by Fan et al [22] studied detailed dislocation and void evolution in NiCoFeCr with respect to temperature and dose, and our current work mainly studies the matrix concentration variation associated with preferential diffusion in irradiated NiCoFeCr
Summary
High-entropy alloys (HEAs) have attracted significant research interests due to their excellent strength, ductility, and radiation resistance [1, 2, 3, 4, 5, 6] These superior properties make HEAs suitable for a variety of applications, especially as potential structural materials for advanced nuclear energy systems [7, 8, 9, 10]. The underlying mechanism leading to the unusual distribution of voids at low doses remains unclear Uncovering this mechanism may explain the dramatic transition of void growth with dose and reveal in what HEA systems the transition could happen
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