Nanometallic Glasses: Size Reduction Brings Ductility, Surface State Drives Its Extent

Abstract

Figure S1: Average Young's moduli for FIB and EP samples across ten independent specimens (five of each type). EP samples show a slightly lower modulus, but it is within one standard deviation.

Ductility and work hardening in nano-sized metallic glasses

“…Stress-strain data in these samples show distinct work hardening to $25% true strain and permanent plastic deformation upon unloading past the elastic limit. 9 Similar plasticity and necking have been reported for electroplated (EP) NiP MGs with diameters of 100 nm and below that were fabricated with and without the use of focused ion beam (FIB), 10 as well as for melt-spinned CuZr MGs with diameters 70-120 nm fabricated with FIB. 11 Necking and strain hardening are typical for crystalline metals and metal alloys, whose plastic flow is enabled by the motion and interactions of dislocations but are anomalous for amorphous metals.…”

“…Recent in-situ observations of a brittle-to-ductile transition emergent in nanometer-sized metallic glasses under tension suggest a mechanism for plasticity not involving shear bands. [8][9][10][11] In one such work, Jang et al demonstrated that Zr 35 Ti 30 Co 6 Be 29 metallic glass nano-cylinders underwent a transition from catastrophic shear banding in samples with diameters greater than 100 nm to a ductile necking-to-shearbanding deformation prior to failure in thinner samples. Stress-strain data in these samples show distinct work hardening to $25% true strain and permanent plastic deformation upon unloading past the elastic limit.…”

“…It has been speculated that size-induced brittle-to-ductile transition may be caused by a surface modulated mechanism that governs extendibility, an idea supported by the additional enhancement in ductility in ion-irradiated samples. 9,10,12 Such a mechanism would have consequences for both the sample size as well as sample surface energy state. To explore the physical origins of emergent plasticity and hardening in nano-sized metallic glasses, we performed insitu nano-tensile experiments on $70 nm-diameter electroplated NiP MG samples, whose surface area-to-volume ratio is $0.06, representing a 50% enhancement in the relative role of the sample surface compared to 0.04 for $100 nm samples.…”

Effects of Helium Implantation on the Tensile Properties and Microstructure of Ni73P27 Metallic Glass Nanostructures

“…To obtain more accurate results, instead of using the raw data of the measured displacement signal, frames from the in-situ SEM videos were examined to determine the actual displacement. This technique allows for more reliable strain data and has been used successfully in many publications [5][6][7] . The InSEM system (Nanomechanics, Inc.) used has a load resolution of 3 nN and a displacement resolution of 0.0002 nm.…”

3D nano-architected metallic glass: Size effect suppresses catastrophic failure

“…The "smaller is more ductile or deformable" size effect frequently observed in metallic glass nanopillars has predominantly been rationalized by the high surface-to-volume ratio in nanopillar samples, which increases the energetic cost of forming and propagating a shear band compared to homogeneous deformation [6,8,9,[48][49][50]. For a sample of dimension, , the energy required for a crack-like shear band to propagate scales with the sample cross-sectional area, or while the energy required to deform a sample in a homogeneous way scales with the sample volume, or .…”