Radiation-enhanced structural disorder and hardening in AlCrFeVTi high-entropy amorphous alloy thin films for lead-cooled fast reactors

This study investigates the irradiation tolerance of novel AlCrFeVTi high-entropy alloy (HEA) thin films fabricated using magnetron sputter coater and subjected to low-dose He⁺ ion irradiation at room temperature. The films exhibit a fully amorphous structure and uniform thickness of ∼1400 nm. Helium ion irradiation was performed at fluences varying from 2 × 10¹⁵ to 5 × 10¹⁶ ions/cm² using a 4 MV accelerator. Structural evolution was assessed by XRD, TEM, and SAED, revealing retention of amorphicity across all doses, with local ordering changes analyzed via high-resolution TEM and auto-correlation mapping. Surface morphological changes and progressive roughening, were quantified by SEM and AFM, with RMS roughness increasing from 5.16 nm (as deposited) to 21.0 nm (1.7 dpa). Nanoindentation demonstrated irradiation-induced hardening (7.6 → 9.6 GPa) and modulus enhancement (157.7 → 182.2 GPa), consistent with finite element simulations of stress distribution. These results establish a clear structure–property relationship, showing that irradiation-driven local disorder enhances mechanical strength without triggering crystallization or embrittlement. The demonstrated radiation tolerance highlights amorphous AlCrFeVTi films as promising candidates for protective coatings in advanced nuclear energy systems.