Atomistic simulation of yield and plastic deformation in bulk nanostructured metals

The influence of dislocation density on yield strength, which is a key factor in the anomalous deformation behavior in UFG metals, was investigated by huge scale atomistic simulations. Polycrystalline models with intragulanular Frank-Read sources were constructed to elucidate the relationship between the inter- and intra-granular plastic deformation processes and the mechanical properties. Then the uniaxial tension and compression were applied to the polycrystalline copper. Consequently it was found that Frank-Read sources were activated prior to intergranular dislocation emission, and the yield event of the whole system seems to occur when some dislocation sources activated. The yield stress is strongly influenced by the number of intragranular dislocation sources, i.e., dislocation density. Additionally, the Bauschinger effect of UFG metals is caused by the change in dislocation density in the process of forward and backward deformation.