Molecular dynamics simulation of effect of void on subsurface defect evolution in nano-cutting of γ-TiAl alloy

Abstract

Defects such as voids are an unavoidable occurrence during the processing and preparation of materials, which can significantly impact their cutting performance and surface quality. To investigate the influence of void defects on single-crystal γ-TiAl during the cutting process, this study employed molecular dynamics simulations to establish cutting models featuring voids of varying sizes. Utilizing dislocation theory, we analyzed defect evolution and atomic plastic flow in response to these voids from an atomic perspective. The findings indicate that, compared to a defect-free substrate, the presence of voids leads to the formation of four distinct zones within the cutting zone: the chip zone, extrusion zone, stagnation zone, and surface formation zone. The extrusion zone facilitates increased atom displacement into the voids, thereby reducing resistance encountered by the tool and resulting in a decrease in cutting force. Furthermore, dislocation density, subsurface defect layer depth, and stress distribution are all influenced by void size. During cutting operations, plastic deformation is likely to occur both within the voids themselves and in surrounding regions; consequently, some stress is dissipated. Over time, these voids may evolve into clusters that remain embedded within the substrate material, thereby affecting subsurface defect layer depth. Small-sized voids (R ≤ 0.4001 nm) serve as sources for dislocation emission while larger-sized voids (R ≥ 0.4001 nm) impede dislocation nucleation expansion. The results presented herein contribute valuable insights into understanding nano-cutting processes involving defective γ-TiAl at a microscopic scale, offering essential theoretical support for optimizing its cutting procedures and enhancing overall processing quality.