Scaling of the ductility with yield strength in nanostructured Cu/Cr multilayer films

At a constant modulation period (λ), nanostructured Cu/Cr multilayer films exhibit ductility scaling linearly with yield strength that varies with modulation ratio. The films with different λ have their own scaling relationship. The scaling slope for λ = 25 nm is much sharper than that for λ = 50 nm, indicating that a stronger interface constraint causes a larger reduction in ductility. These scaling relationships can be understood by referring to macroscopic fracture models based on a critical stress criterion.