Enhanced surface bombardment resistance of the CoNiCrFeMn high entropy alloy under extreme irradiation flux

Abstract

We have investigated the response of the high entropy alloy of CoNiCrFeMn to the bombardment under extreme irradiation flux by means of molecular dynamics simulations. Compared to pristine Ni single crystalline, the CoNiCrFeMn HEA had less point defects during a single primary knock-on atom process. The average depth of defects was shallower. For consecutive bombardments, the CoNiCrFeMn HEA demonstrated much higher surface irradiation resistance than pristine Ni. Under the irradiation flux of 5.59 × 1027 n/(m^2*s), the number of defects in Ni gradually increased and was proportional to the number of bombardments, till the formation of dislocation which led to a boost of the defects. On the contrary, the number of defects in CoNiCrFeMn HEA was much less and stable, appearing to be insensitive to the number of bombardments and suggesting good radiation resistance. Such radiation resistance of CoNiCrFeMn HEA was attributed to the lattice distortion and sluggish diffusion of atoms, which could enhance the recombination of defects. Under the irradiation flux of 1.68 × 1028 n/(m^2*s), the boost of the defects in Ni occurred at lower number of bombardments. In addition, under both the irradiation flux of 5.59 × 1027 and 1.68 × 1028 n/(m^2*s), CoNiCrFeMn HEA had a smaller number of point defects and the defects were well dispersed. Our results showed that compared with Ni matrix, CoNiCrFeMn HEA had higher surface bombardment tolerance. This study might be helpful in the design of first-wall materials under the extreme irradiation flux.