2, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
In this study, the mechanical behavior of metallic nanocomposites with bicontinuous structures has been studied using in situ nano-pillar compression testing in SEM. The nanocomposites with ligament sizes ranging from 2.5 nm to 15 nm were prepared by co-sputtering Cu and Mo with a nominal 50/50 atomic ratio at high temperatures. By varying the deposition temperature from 600oC to 800oC, the morphology of the nanocomposite changed from an anisotropic structure with alternating vertical Cu/Mo nanolayers to a more isotropic structure with intertwined Cu/Mo phases. During the compression tests, both morphologies exhibited large compressive strains (> 30%) at extremely high stresses (> 2 GPa) with maximum flow stresses approaching 3 GPa. Kink bands were observed in the anisotropic samples through post-mortem TEM investigation, whereas uniform deformation was observed in the isotropic samples. Slip along the aligned interfaces that are weak in shear is proposed to account for the strain localization in the kink bands.