Novel fusion and generation-IV fission reactors demand development of new structural materials with exceptional performance under harsh environments. It was shown that increase of entropy improves radiation endurance by impeding relaxation processes and stabilizing non-equilibrium states [1]. In multicomponent solid solutions, such as high-entropy alloys (HEAs), configurational entropy is elevated. Therefore, these materials might have improved radiation resistance properties. Most HEAs are not single-phase alloys, having ordered and disordered domains, such as A2 (BCC) and B2. To isolate the response to irradiation of one of these phases, AlFeCoNi medium entropy alloy (MEA) was chosen, since it comprises of a single B2 phase [2]. In current research, AlFeNiCo alloy was irradiated with Ar ions using 〖10〗^16, 〖10〗^17 and 〖10〗^18 ions/(cm^2 ) doses at temperature of (543)±50°K . Two of the drawbacks of ion irradiation is their short penetration depth and the continuously varying defect concentration over the penetration depth using different dose of ions. Therefore, for a correct comparison of radiation effects, the regions at well-defined depths from the surface must be able to be sampled reproducibly. To meet this requirement, Transmission Electron Microscopy (TEM) samples were irradiated by Ar ions. TEM analysis was performed before and after irradiation. It was found that radiation damage mechanism in B2 single phase AlFeCoNi MEA consisted of dislocation accumulation leading to recrystallization. Increasing the dose, multiplication of dislocations (increasing their density) and local disorder, caused formation of additional type of dislocations. At higher fluences, the dislocations rearranged into walls, forming cellular microstructure. Moreover, at the highest dose – recrystallization occurred, resulting in small equiaxed grains similar in size to the dimensions of the dislocation cells, observed in the sample irradiated at a lower dosage.

References

[1] T.Egami, W.Guo, P.D.Rack, T.Nagase, Met Mat Trans A 45 (2013) 180.

[2] G.Hillel, L.Natovitz, S.Salhov, S.Haroush, M.Pinkas, L.Meshi, Metals 10 (2020) 1275.