Irradiation Enhances Strength and Deformability of Nano-Architected Metallic Glass

Abstract

The quest for radiation-damage tolerant materials has found good candidates in nanoporous metals, whose abundance of free surfaces provides ample sinks for radiation-induced defects, as well as in metallic glasses, whose characteristic failure via shear banding can be alleviated by irradiation. This type of catastrophic failure in metallic glass can also be suppressed by reducing their dimensions to the nanoscale. To combine the beneficial effects of resilience against irradiation in materials containing many free surfaces and nano-sized metallic glasses, the authors fabricate Zr–Ni–Al metallic glass nano-architecture and irradiate them with 12 MeV Ni^(4+) ions. These 3D nanolattices are composed of hollow beams of sputtered metallic glass with beam wall thicknesses ≈10–100 nm, with a relative density of ≈5%, which renders them to be 20 times lighter than their bulk-level counterparts. The authors find that the thickest-walled nanolattices, those with a median wall thickness of ≈88 nm, are able to withstand irradiation without significant contraction; all other substantially shrunk; and collapsed upon irradiation. In situ nanomechanical experiments on the irradiated samples compressed inside a scanning electron microscope (SEM) reveal substantial improvement in mechanical response upon irradiation, with an average increase in yield strength of 35.7% and a significant enhancement in deformability. Enhanced deformability upon irradiation is apparent from the nanolattices' accommodation of larger strains before any kind of failure, as well as the presence of smaller strain bursts and stress drops throughout the stress–strain response. The irradiated nanolattices are largely intact after compression, with in situ SEM videos demonstrating a layer-by-layer like collapse in the irradiated nanolattices in contrast to the catastrophic failure with complete destruction of the failed layers observed in equivalent as-fabricated samples. This work points to nano-architected metallic glasses being a promising candidate for creating ultra-lightweight, radiation tolerant materials, and irradiation as a promising technique for improving the mechanical response of metallic glass nanolattices with stiffness on the order of 250 MPa.

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