Effects of grain size and indentation sensitivity on deformation mechanism of nanocrystalline tantalum

Nanoindentation process is performed by molecular dynamics simulations to investigate the plastic deformation phenomena and mechanical properties of the polycrystalline tantalum (Ta) substrate. The comparison of mechanical behaviors between the single crystal and polycrystalline Ta is analyzed. The effects of grain size, indenter radius, indentation velocity, and temperature are deeply investigated. Further, the important factors of mechanical property such as the plastic deformation, dislocation, amorphization process, indentation force, yield pressure, and von Mises stress are evaluated. The results show that the phase transformations and dislocations almost absent in the grains. Instead, the dislocations densely occur in the grain boundaries, the amorphization regions are formed around the indentation areas and develop along the grain boundaries. The high von Mises stresses are mainly distributed around the indentation areas and in the grain boundaries. The single crystal tantalum shows better mechanical characteristics than the polycrystalline tantalum such as harder to deform, higher yield pressure, and lower dislocation. •The mechanical properties and plastic deformation phenomena of the polycrystalline Ta are investigated by MD simulations.•The dislocations densely occur in the grain boundaries.•The amorphization regions are formed around the indentation areas and develop along the grain boundaries.•The high von Mises stresses are mainly distributed around the indentation areas and in the grain boundaries.•The single crystal Ta shows the better mechanical characteristics than the polycrystalline Ta.