Effect of Initial Indentation Position on Plastic Deformation Behaviors of Polycrystalline Materials via Molecular Dynamics Simulation

Polycrystalline materials can be divided into four types of microstructural components, including grain cell (GC), grain boundary (GB), triple junction (TJ) and vertex points (VP). Nanoindentation at different microstructural components on the polycrystalline materials surface can lead to different plastic deformation behaviors of the polycrystalline materials. Due to experimental limitations, the indentation-induced internal stress and defect evolution process are difficult to investigate directly, especially for the polycrystalline materials with grain size less than 100nm. The molecular dynamics (MD) simulations were performed to unravel the initial indentation position effect on the elasticity/plastic deformation mechanism of polycrystalline copper. The results reveal that the initial indentation position governs the indentation force variation and defect distribution range due to the different dimensionalities of the microstructural components. The defect propagation as well as the internal stress transmission in the GC regions tend to transfer to the low-dimensional microstructural components of the interfaces. In addition, the atomic internal stress and potential energy accumulation/release of the microstructural component atoms during the nanoindentation process are also investigated, revealing that the atomic internal stress and potential energy in the VPs vary earliest, followed by the TJs, GBs and GCs.