Structural responses of heterogeneous nanocrystalline/amorphous laminated alloy under irradiation

Abstract

To reveal the structural responses of a heterogenous nanocrystalline/amorphous laminated (HNAL) alloy under irradiation, a reliable HNAL model composed of amorphous Zr2Cu and FCC Cu nanocrystalline layers was developed and comparatively evaluated with a Cu/Zr2Cu heterogeneous nanocrystalline laminated (HNL) model by molecular dynamics (MD) simulations in a comprehensive microstructural evolution study. Irradiation-induced vacancies, defects and major clusters destroyed with the expansion of collision cascades were fully recovered in HNAL with a near-perfect structural distribution, but the HNL demonstrated a weak recovery ability of its fine structures. The change of melted zones stimulated an unusual dynamic of the Cu/Zr2Cu composition line in the HNAL model, energizing the Cu nanocrystalline layer to be as competitive as the amorphous zone for full self-recovery evidenced by the emergence of a supercooled liquid zone in the amorphous and nanocrystalline Cu regions as the melt super-quenched. The affinity of the Cu nanocrystalline region to capture a significant stretch of the Zr37Cu63 supercooled liquid region provoked significant composition and structural fluctuations in the energetics interplay of both the intrinsic hetero-structure (supercooled liquid-nanocrystalline) and hetero-composition (Zr2Cu-Cu) systems around the composition line, causing stimulated nucleation centers in the FCC Cu region to evoke a remarkable supercooled to crystalline transition phenomenon in the HNAL model. This unique effect of full recrystallization from the Zr37Cu63 supercooled liquid to nanocrystalline Cu validates the effective self-healing ability of the HNAL and underscores the structural mechanism of the extremely high self-healing behavior in the nanocrystalline region that underpins the ultra-high structural stability of the HNAL model under irradiation. These novel discoveries will potentially facilitate the tailoring of hetero-composition and hetero-structure materials in advanced nuclear material applications.