Hierarchical-interface design for stable helium storage and structural evolution in homogeneous nano-multilayered Al1.5CoCrFeNi high entropy alloy films

Hierarchical interfaces and nanometer grain boundaries (GBs) were synchronously designed inside the homogeneous Al1.5CoCrFeNi high entropy alloy (HEA) nano-multilayered films, in which each lamellae was composed of nano-crystals to construct helium (He) ion radiation-tolerant materials used for future advanced nuclear-energy system. The depth profile of He behavior and phase-structure evolution in the irradiated [Al1.5CoCrFeNi (10 nm)]30 and [Al1.5CoCrFeNi (30 nm)]10 nano-multilayered films were investigated systematically. Results indicated that the He bubble size in multilayered film exhibited a reduction tendency and a wide distribution feature as the individual-thickness increased from 10 nm to 30 nm, demonstrating inverse results with previous heterogeneous-interface modeling. Reduced bubble pressures were identified in the two kinds of nano-multilayered HEA films, indicating that the coexistence of nanocrystals and homogeneous-interfaces was beneficial to manage He distribution and prolonged bubble growth effectively by tailoring each-lamellae size in these two kinds of multilayered Al1.5CoCrFeNi HEA films. Partial phase transformation from body-centered-cubic (BCC) to face-centered-cubic (FCC) structure was induced through promoting the structural evolution between the irradiation-induced amorphous regions and compositional reorganization in these nano-multilayered HEA films upon irradiation. The interfaces and GBs promoted the annihilation of these defects and further facilitated the self-healing behavior. Such hierarchical-interface in the HEA provides a novel strategy for the effective He entrapment in improving radiation tolerance and a potential possibility of real-application.