Dependence of Plastic Stability on 3D Interface Layer in Nanolaminated Materials

The nanolaminated materials generally exhibit poor plasticity due to the fast onset of shear instability. Engineering interface structure is an effective approach for enhancing plasticity via postponing or suppressing the shear instability. Here, we introduce 4 nm thick CuNb 3D amorphous interface layers and Nb 3D crystalline interface layers in Cu nanolaminated materials, respectively. In situ micro-pillar compression tests show that samples with crystalline interface layers exhibit shear instability, while the samples with amorphous interface layers display uniform deformation. Since the plastic deformation of the single-crystal crystalline interface layer is anisotropic, except for well-aligned slip systems, dislocations on other slip systems have a poor ability to transmit the 3D crystalline interface layer, leading to localized dislocations pileups and shear instability. In contrast, the amorphous interface layer which is plastically isotropic accommodates dislocations from arbitrary slip systems of the matrix, which can alleviate the stress concentrations at the interface, and thus suppresses the shear instability.