Effects of dislocations on He bubble behaviors in Al0.1CoCrFeNi high-entropy alloys at 773 K and 973 K

Abstract

The evolutions of He bubbles in Al_0.1CoCrFeNi high-entropy alloy (HEA) with different dislocation densities were investigated after 400 keV He⁺ irradiations at 773 K and 973 K to a fluence of 1.5 × 10¹⁶ cm⁻². The introduction of dislocations decreases the average size of He bubbles and delays the volume swelling at both temperatures. At 773 K, the homogeneous nucleation of He bubbles at vacancy clusters are dominant. Since the dislocations can absorb the neighboring vacancies and deposited He atoms, the nucleation and growth of He bubbles are suppressed and both the average size and density of He bubbles are decreased with the increase of dislocation density. When the temperature increases to 973 K, the long range diffusion of He is greatly enhanced and the homogeneous nucleation transforms to heterogeneous nucleation. The increase of dislocation density provides more trapping and nucleation sites, thus, resulting in the decrease of average sizes and increase of density of He bubbles. Furthermore, the distribution depth ranges of He bubbles are decreased with dislocation density at both temperatures, which is probably due to the fast migration of He atoms along dislocations. This work demonstrates the beneficial effects of introduction of dislocations on resistance of HEAs to He bubbles, which would provide helpful evidences for designing and optimizing deformation processes to improve the irradiation resistances of HEAs.