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

We investigate the mechanical behavior of 3D periodically architected metallic glass nanolattices, constructed from hollow beams of sputtered Zr-Ni-Al metallic glass. Nanolattices composed of beams with different wall thicknesses are fabricated by varying the sputter deposition time, resulting in nanolattices with median wall thicknesses of similar to 88 nm, similar to 57 nm, similar to 38 nm, similar to 30 nm, similar to 20 nm, and similar to 10 nm. Uniaxial compression experiments conducted inside a scanning electron microscope reveal a transition from brittle, catastrophic failure in thicker-walled nanolattices (median wall thicknesses of similar to 88 and similar to 57 nm) to deformable, gradual, layer-by-layer collapse in thinner-walled nanolattices (median wall thicknesses of similar to 38 nm and less). As the nanolattice wall thickness is varied, large differences in deformability are manifested through the severity of strain bursts, nanolattice recovery after compression, and in-situ images obtained during compression experiments. We explain the brittle-to-deformable transition that occurs as the nanolattice wall thickness decreases in terms of the smaller is more deformable material size effect that arises in nano-sized metallic glasses. This work demonstrates that the nano induced failure-suppression size effect that emerges in small-scale metallic glasses can be proliferated to larger-scale materials by the virtue of architecting. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.