Mechanical properties of fcc/fcc Cu/Nb nanostructured multilayers

The phase transition of Nb from body-centered cubic (bcc) to face-centered cubic (fcc) has been found in Cu/Nb nanostructured multilayers with modulation period (λ) spanning from 5 to 300 nm, and was analyzed by using a thermodynamic model. As λ decreases, the strength of multilayers increase and approach saturation of ∼2.88 GPa at a few nm layer thickness. Size dependent strengthening in present fcc/fcc Cu/Nb multilayers is explained in terms of dislocation based strengthening mechanisms. The enhanced modulus of fcc/fcc Cu/Nb is also observed.

► Phase transition of Nb occurs in Cu/Nb multilayers.
► Hardness is assessed by related dislocation mechanism.
► Fcc/fcc Cu/Nb multilayers shows higher interface strengthening ability than fcc/bcc ones.
► Enhanced modulus is caused by the compressed out-of-plane interplanar spacing of Nb.