Microstructure evolution under He2+ ions irradiation in a high entropy alloy designed by constructing nanostructure engineering

Abstract

This study aims to reduce the size and density of He bubbles and dislocation loops during the irradiation process by constructing nanostructure engineering through precipitation. The Ni35(CoFe)55V5Nb5 high-entropy alloy (HEA) with solid solution and aging states underwent He2+ ions irradiation (500 keV at a fluence of 1017 ions∙cm−2) at 500 °C. The results indicate that the preexisting nanoprecipitates increased the surface area for He atoms adsorption, and improved the ability of the alloy to suppress the coarsening of He bubbles. In the aged HEA, He bubble size decreased (∼3.3 ± 0.4 nm), and density significantly reduced (0.58 ± 0.14 × 1023 m−3) compared to the solid solution HEA (∼6.1 ± 0.3 nm, 2.42 ± 0.15 × 1023 m−3). Moreover, the preexisting nanoprecipitates coordinate the movement and recombination of irradiation defects, which overwhelms the energy driving force that improves the stability and growth of dislocation loops due to the reduction of stacking fault energy, thereby suppressing the formation and growth of dislocation loops. The aged HEA exhibited reduced size and density of dislocation loops (∼6.3 ± 0.5 nm and 0.78 ± 0.15 × 1020 m−3) compared to the solid solution HEA (∼8.5 ± 0.6 nm, 3.83 ± 0.13 × 1020 m−3).