This presentation will focus on (1) the effects of length scale and interface on the mechanical properties, and (2) mehcanical and thermal stability of the nanoscale structures in several model metallic multilayered systems. We have utilized conventional, analytical, and high resolution transmission electron microscopy to establish an atomic scale description of the microstructure, deformation structure, and local composition profile. The mechanical behavior has been characterized by nano- and micro- indentation, and by micro-tensile testing. Calorimetric measurements were made to determine the amount of strored energy on the degree of deformation. A strong scale effect on the mechanical behavior including the deformation structure, hardness, and fracture characteristics has been observed. In addition, both cold rolling and annealing of self-supported samples were performed to characterize the mechanical and thermal stability of metallic multilayers. The unusual stability of the layered structure and texture that was observed reflects the operation of new kinds of deformation mechanisms. Atomistic simulations have been carried out to examine slip behavior in coherent and semicoherent layered systems. The results reveal complex interfacial structure in response to applied stresses, and shed light onto the unusual deformation processes.
This work has been conducted at Los Alamos National Laboratory under the support of DOE Office of Basic Energy Sciences, Division of Materials Sciences and Engineering.