Atomic-scale study of dislocation-grain boundary interactions in Cu bicrystal by Berkovich nanoindentation

The plastic behavior of metal materials is mainly dominated by dislocation movement, whereas for polycrystalline metals, dislocation-grain boundary (GB) interactions play a significant role in the mechanical response. In the present work, deformation mechanisms of single crystal and bicrystal Cu workpieces subjected to Berkovich nanoindentation are studied by experiments and molecular dynamics (MD) simulations. The numerical model considers crystallographic orientations of the individual grains determined by electron backscatter diffraction (EBSD) characterization of the designated location on the polycrystalline surface. Experimental results indicate as the distance between the indentation and the GB decreases, the hardness of the tested specimen decreases and Young's modulus increases. Meanwhile, the corresponding simulation results reveal the anisotropic nature of dislocation evolution under the indenter for different crystallographic orientations of the single crystal Cu. Furthermore, GB as a complicated factor to the dislocation motion leads to the unusual deform behavior of materials in the vicinity of the GB, and dislocation-GB interactions introduce different deformation mechanisms. For the GB with a high angle of [1-11] 59.8°, dislocation slip along the GB is believed to play an important role in the decrease of the hardness.