Internal stress and mechanical deformation of Al and Al/Ni multilayered nanowires

Abstract

Isothermal molecular dynamics is used to study the correlation between the spatial distribution of internal stress and mechanical deformation of a 6.7-nm-diameter Al nanowire with <1 0 0> axis is subjected to an external uniaxial stress. The stress–strain relationship is asymmetrical. In the case of a tensile load, the internal stress distribution is found to result from the interplay between structure and morphology. As a general rule, yielding nucleates where the internal stress gradient is the highest. If the Al wire is interfaced with a harder material—Ni in this study—the highest gradients occur at the interface, where a characteristic interfacial stress pattern is induced. Remarkably, compressive and tensile yield strengths are found to be unaffected by the hard/soft interfaces. The structure of the stress–strain relationship is found to correlate with identified discrete plastic events. These may be complex, involving interactions between partial dislocations, stacking faults, surfaces and interfaces, internal stress localization and release.