Slip bands in Cu/Nb nanolaminates with thick 3D interfaces

Metallic nanolaminates are well recognized for their high strength but at the cost of reduced deformability. Recently, in the Cu/Nb system, this trade-off was overcome by the introduction of thick “3D” interfaces, which caused simultaneous increases in strength and deformability. Since then, the origins of 3D interface strengthening have been studied, but those underpinning the increased deformability have not. In this work, we study the evolution of slip bands in the Cu/Nb system with conventional sharp (2D) or thick 3D interfaces using the slip band fast Fourier transform model. The simulations suggest that slip will localize first in the Cu nanolayer. The Nb slip bands are more likely to form from transmission of a Cu slip band through the interface than independently. Such slip transmission events are predicted to increase the amount of lattice reorientation, which can trigger an instability. Relative to a 2D interface, a 3D interface substantially raises the applied stress required for Cu-to-Nb slip transmission and for the formation of independent slip bands, events that ultimately reduce deformability by producing large lattice rotations and triggering shear instabilities.