Effects of crystallographic orientations and grain boundaries on nanoscratching behaviour of unique bi-crystal Cu

Abstract

Microstructural-related deformation behaviour at grain levels significantly affects mechanical properties of crystalline materials. Particularly, crystallographic orientations and grain boundaries play crucial roles in the friction and wear performance of polycrystalline materials at the microscale. In this study, experiments and corresponding crystal plasticity finite element simulations are conducted using a spherical indenter to illustrate the underlying effect of crystallographic orientations and grain boundaries on the nanoscratching behaviour of a unique bi-crystal Cu. The indenter size and process parameters in simulations are consistent with experiments, and crystallographic orientations of two designated individual grains on the polycrystalline surface are determined via electron backscatter diffraction pattern. The simulation results show that crystallographic orientations significantly affect the plastic deformation of the target material by activating different slip systems. Grain boundary can act as an obstacle as well as a starting point of the dislocation movement, leading to anisotropic wear behaviour in the vicinity of the grain boundary. Furthermore, the simulated scratched surface morphology of the bi-crystal Cu quantitatively shows good agreement with the experimental results.