Deformation Mechanisms of Copper Nanowires Under Tensile Loading

Abstract

Molecular dynamics (MD) simulations with an embedded atom method (EAM) potential are carried out to analyze the deformation mechanisms and the size and strain rate effects in the tensile deformation of single-crystal Cu nanowires. The cross-sections of the wires are squares with dimensions between 5 and 20 lattice constants (or 1.8 to 7.2 nm). Deformations under constant strain rates between 1.67◊10 5 s -1 and 1.67◊10 10 s -1 are analyzed. The analysis focuses on the variation of deformation mechanisms with specimen size and strain rate. It is observed that in small wires stacking faults are formed along alternating (111) planes through the motion of a single dislocation, while the formation of networks of stacking faults, local HCP structure, and twins through nucleation and motion of multiple dislocations are primarily responsible for the progression of plastic deformation in larger wires. As strain rate is increased, dislocation speed increases to accommodate the plastic deformation. However, when the dislocation speed approaches the shear wave speed of the material, a transition of deformation mechanism from sequential propagation of stacking faults through dislocation motion to amorphization is observed. The influences of specimen size and strain rate on the behavior are also discussed.