Influence of tunable interfaces on radiation tolerance and nanomechanical behavior of homogeneous multi-nanolayered Al 1.5 CoCrFeNi high entropy alloy films

Introducing high-density defect sinks, e.g., grain boundaries (GBs) and interfaces, to capture helium (He) atoms and irradiation-induced defects under He + irradiation is a promising strategy for constructing novel nuclear-materials with enhanced radiation tolerance. To understand the vital roles of GBs and interfaces on the irradiation response in high entropy alloys (HEAs), high-density GBs and homogeneous interfaces between layers were firstly introduced into multi-nanolayered Al 1.5 CoCrFeNi HEA films by tailoring the nominal monolayer thickness ( h ) ranging from 2 to 100 nm. The multi-nanolayered HEA films were then irradiated by 60 keV He + at a fluence of 1 x 10 17 cm -2 . The results show that the He bubbles with size of 1-2 nm were preferentially distributed along the GBs within the films and the phase structure kept stable in the irradiated HEA films with less interfaces (such as h = 100 nm). This suggests that the He bubbles mainly distributed at GB sinks due to the high-density GB intersections acted as dominant defect-sinks to trap He atoms. While both the distribution of He bubbles throughout the interfaces and the partial BCC -> FCC phase transformation due to radiation-induced segregation were disclosed by introducing numerous interfaces in the irradiated multi-nanolayered HEA films ( h = 10 and 30 nm). The corresponding intrinsic mechanism of He behavior was elucidated based on the interactions between the He defects and the nano-GBs or homogeneous interfaces. The underlying mechanisms of irradiation-induced phase transformation were explained by the relief of compression stress and the radiation-induced segregation behavior by vacancy-flux. Also, the roles of interfaces and GBs on the irradiation swelling and nano-mechanical properties of the HEA films were also revealed by the systematic investigations.