Plastic deformation mechanisms and size effect of Cu50Zr50/Cu amorphous/crystalline nanolaminate: A molecular dynamics study

Abstract The plastic deformation behaviours of Cu 50 Zr 50 /Cu amorphous/crystalline nanolaminate were studied at the atomic scale using molecular dynamics simulations. Unlike the limited plasticity due to the highly localized shear banding in pure metallic glass, the nanolaminate undergoes a pronounced homogeneous deformation under applied tensile strains greater than 8.0% that is ∼36.4% larger than that of pure metallic glass. This plasticity enhancement is attributed mainly to the suppression of the nucleation and propagation of the shear band in the nanolaminate. The scattered immature shear band or shear transformation zones and dislocations cooperate to form a network to transmit the strain within the entire sample. Significant size effects are demonstrated, revealing that both the strength and elongation-to-failure reach their respective peak values at a layer thickness d of approximately 4 nm and that the relationship between strength and d is well-explained by the confined layer slip (CLS) model. In the case of d values from 27 nm to 4 nm, the nanolaminate undergoes a transition from inhomogeneous deformation to homogeneous deformation. When d decreases to less than ∼4 nm, the nanolaminate exhibits inhomogeneous deformation because of the destruction of the amorphous/crystalline interface. On the basis of this mechanical mechanism, the present study provides an approach for strengthening and toughening the amorphous/crystalline nanolaminate by adjusting the layer thickness.