Layer thickness dependent strengthening and strain delocalization mechanism in CuTa nanopillars with nanoscale amorphous/amorphous interfaces

Introducing amorphous/amorphous interfaces in metallic glasses offers an effective strategy to address the strength-plasticity trade-off by suppressing the strain localization. Elucidating the underlying size-dependent deformation mechanisms is crucial for designing strong and ductile amorphous nanolayered materials. Herein, molecular dynamics simulations are conducted to investigate the deformation behaviors of Cu₇₀Ta₃₀/Cu₃₀Ta₇₀ amorphous/amorphous nanopillars (AANPs) under compression, focusing on the intrinsic size effect of amorphous layer thickness. The results indicate a critical layer thickness of approximately 6.7 nm, below which an inverse Hall-Petch relation occurs. This transition is attributed to a shift in dominant deformation mode from the necking and localized deformation to the relatively homogeneous deformation as the layer thicknesses decreases. These A/A interfaces could be considered as a third medium phase in nanolaminates, especially when the thickness is very low, down to only a few of nm. The mechanical properties and deformation behavior of transitional interface phase lie between those of soft and hard phases, balancing heterogeneous deformation between hard and soft layers and resulting in homogeneous flow deformation of specimen with thinner amorphous layer. These findings provide insight for designing ductile amorphous materials through architecting nanoscale amorphous/amorphous interfaces.