Size-dependent deformation mechanisms in copper gradient nano-grained structure: A molecular dynamics simulation

Gradient nano-grained (GNG) structures exhibit an excellent combination of high strength and toughness. In this paper, molecular dynamics (MD) simulations have been utilized to investigate the tensile properties and related deformation mechanisms of GNG copper structures. Results show that larger gradients give higher strength within a certain size scale range. In the GNG structure, the grain size heterogeneous leads to the non-uniform stress distribution, and the synergistic deformation induced inverse Hall-Petch phenomenon is observed. Furthermore, while both large- and small-grained layers begin to have plastic deformation simultaneously, the dominant deformation mechanism is found to vary with grain size. For grains with 30-100nm, dislocation slips emitted from grain boundaries (GBs) dominate deformation, whereas GB activities, such as GB sliding and/or grain rotation, become the main deformation carrier for grains with 10-20nm. Our results provide a deeper understanding of the deformation mechanisms of GNG copper structures and give guidance for design GNG copper structures.