Metallic nanowires had many attractive properties such as ultra-high yield strength and large tensile elongation. However, recent experiments showed that metallic nanowires often contained grain boundaries, which were expected to significantly affect mechanical properties. By using molecular dynamics simulations, here, it was demonstrated that polycrystalline Cu nanowires exhibited tensile deformation behavior distinctly different from their single-crystal counterparts. A significantly lowered yield strength was observed as a result of dislocation emission from grain boundaries rather than from free surfaces, despite of the very high surface to volume ratio. Necking starts from the grain boundary followed by fracture, resulting in reduced tensile ductility. The high stresses found in the grain boundary region clearly played a dominant role in controlling both inelastic deformation and fracture processes in nanoscale objects. These findings had implications for designing stronger and more ductile structures and devices on nanoscale.

Grain Boundary Effects on Plastic Deformation and Fracture Mechanisms in Cu Nanowires -: Molecular Dynamics Simulations. A.Cao, Y.Wei, E.Ma: Physical Review B, 2008, 77[19], 195429 (5pp)