Abstract
Nanoscale metal-metal multilayered composites, particularly face-centered cubic (FCC) / body-centered cubic (BCC), exhibit extraordinary mechanical properties due to very high flow strength and stable plastic flow to large strains. These properties are mainly due to the dislocation plasticity mechanisms of dislocation pile-up, confined layer slip and interface crossing of dislocations. This Ph.D. dissertation aims to extend the current knowledge of interfaces in nanoscale FCC/BCC multilayered composites in relation to their roles in fracture. A novel experimental technique known as the in situ microfracture technique using clamped beam bending was applied to dive into the deformation mechanisms in these composites and identify the key interface interaction parameters. Variations of crystallographic interfaces of these nanocomposites were created through two fabrication processes of physical vapor deposition (PVD) and accumulative roll bonding (ARB). Factors such as the heat of mixing, the crystallographic orientation and grain morphology in the multilayers influence the mechanical properties of these nanocomposites. A new functional property, in addition to their mechanical properties, was discovered through the identification of these factors. A linear trend of resistivity versus true strain for strains more than 3.5 % was observed for Cu/Nb multilayered nanocomposites, suggesting a significant regime for use in strain sensor/detection/monitoring capability.