Deformation Behavior of Nanostructured Metallic Multilayers

Metallic multilayers, composed of alternating layers of soft metals, are shown to possess ultra-high strengths when the bilayer periods are on the order of a few nanometers. In fact, the strength of materials may be within a factor of two to three of the theoretical strength limit. The dependence of strength on the bilayer period for these multilayers synthesized by vapor deposition techniques is reviewed. It is shown that deformation mechanisms that operate in micron-scale may not be applicable at the nanometer length scales. Dislocation-based models are developed to predict the transition from bulk-like deformation mechanisms to nano-scale deformation mechanisms, and the results presented in “deformation mechanism maps”. Factors that maximize the rate of hardening with decreasing bilayer period and the maximum strength achieved are discussed.