The Role of Grain Boundaries in Rotational Deformation in Polycrystalline Titanium under Scratch Testing

Abstract

The paper reports on a molecular dynamics simulation of plastic deformation in polycrystalline titanium under scratch testing with explicit account of crystallographic orientations determined by electron backscatter diffraction for individual Ti grains. The simulation shows that the presence of a grain boundary breaks the lattice translation invariance and induces a constrained strain zone in which the deformation changes its dislocation mechanism for rotations such that misoriented local regions appear near the grain boundary. The pattern of consistent dynamic rotations of atoms near the grain boundary is governed by the crystallographic orientation of grains. If the indenter sliding direction coincides with one of the easy slip directions of a loaded grain, the material in the grain boundary region is fragmented and atomic clusters move along the grain boundary plane from the surface deep into the material. The simulation results allow us to explain why the profile of scratches differs depending on the scratching direction.