Atomic migration and defect evolution mechanism in nanoscale cutting of TC4 titanium alloy

The nano-level surface characteristics of TC4 titanium alloy ultra-precision complex components are closely related to their internal damage, which directly affects the stability and service life of the components. This study systematically investigates the influence of nano-cutting depth on ultra-precision cutting of TC4 titanium alloy. When the nano-cutting depth is 10 Å, the shear stress field of TC4 titanium alloy is uniform, the surface roughness (RMS) is minimal (0.548 Å), the total length of dislocation lines is only 1118.4 Å, and the sub-surface damage is the lightest. As the nano-cutting depth increases to 15-25 Å, the thermal effect intensifies the lattice expansion and atomic accumulation, resulting in deterioration of surface quality, with RMS increasing to 1.172 Å at 25 Å. The amount of atoms removed increases linearly with depth, and FCC and BCC phase transformations and microcracks occur in the sub-surface, with 1/3 < 1-100 > dislocations dominating plastic deformation. The average friction coefficient decreases with increasing depth, indicating the coupling of processing geometry and deformation mechanism. Controlling the nano-cutting depth can actively optimize the stress state and control the dislocation structure and sub-surface damage.

This study uses molecular dynamics (MD) simulation method and Lammps software to construct a TC4 titanium alloy ultra-precision cutting model, using Tersoff, Lennard-Jones, and EAM potential functions to describe the atomic interactions (representing the multi-body effects between covalent bonds, van der Waals forces, and metal bonds, respectively). This system simulates the atomic movement, mechanical response, energy field evolution, nano-scale surface formation quality, and defect generation and propagation laws during the cutting process, providing theoretical and numerical support for optimizing its ultra-precision nano-machining process.