Toward an understanding of post-necking behavior in ultrafine-scale Cu/Ni laminated composites

Cu/Ni laminated composites with the same total thickness of 128 gm, but different modulation wavelength lambda (the sum of monolayer thickness of constituent layers) of 32 gm and 3 pm, respectively were prepared using a dual-bath electrodeposition technique. The tensile testing results and the quantitative characterization of strain gradient in the post-necking region of the composites reveal that the lambda = 3 mu m composites have the higher tensile strength and the better strain hardening ability, as well as the stronger resistance to post-necking compared with the lambda = 32 mu m ones. A high density of layer interfaces in the ultrathin laminated composite may play a key role in delaying the development of unstable plastic deformation along the layer thickness direction through periodical strain gradient and a number of geometrically necessary dislocations near the interfaces. Thus, the fatal localized plastic deformation along the through thickness direction has to be spread over along the loading direction, leading to the large neck breadth in the ultrathin laminated composites.