Research Of Plasticity In Copper Nanowire With Non-uniform Distribution Of Twin Boundaries

At the Nano scale, the twin boundary spacing plays a significant role on the initial yield stress of nanowires. It serves as the generator of the repulsive force against the nucleation of dislocations and a linear relationship between repulsive force and the reciprocal of the twin boundary spacing. Molecular dynamics (MD) simulation is performed to investigate the tensile deformation of twinned copper nanowire with non-uniform distribution of twin boundaries. Emphasis is the control mechanism of the initial plastic deformation and the role of two twin boundary spacing played in the initial plastic deformation. Simulation results reveal that the initial yield stress is mainly affected by the total density of coherent twin boundaries and the initial yield stress increases with the total density of coherent twin boundaries increasing.At the same time, when the nanowires with non-uniform distribution of twin boundary enter the initial plastic deformation, dislocation nucleation site is always at the junction of the twin boundary and the free surface. The leading partial dislocation is Shockley partial dislocation and occurs on the twin with the largest twin boundary spacing. It emits from the surface and directly transmits through coherent twin boundaries via the interaction.Finally, the cross-section diameter, the strain rate, temperature and cross-section shape effect to the initial yield stress are systematically discussed. The result shows that the magnitude of the initial yield stress highly depends on the diameter, strain rate, temperature and cross-section shape applied.