Molecular dynamics simulation study of interaction mechanism between grain boundaries and subgrain boundaries in nano-cutting

In nano-cutting, grain boundaries with complex network structures hinder the movement of defects like subgrains in nanocrystalline materials, affecting the surface generation process and mechanical properties of the machined materials. In this work, the interaction mechanism between the grain boundaries and the subgrain boundaries in nano-cutting is investigated by molecular dynamics (MD) simulations. The results show that the extrusion action between the grain boundaries and the cutting tool causes the periodic formation and annihilation of the subgrains in nano-grains. The interactions between the grain boundaries and the subgrains lead to continuous pile-up formation, obvious stresses accumulation, elastic recovery of the machined surface, and periodic oscillation of processing force. This study will be helpful for designing the nano-cutting process to get better surface quality and mechanical properties of nanocrystalline materials.