Molecular Dynamics Simulation on the Nanocutting Mechanism of Polycrystalline γ-TiAl Alloy with Spherical Defects.

This study examines the influence of internal spherical defects on the properties of γ -TiAl alloy, a promising material for the aerospace industry where such imperfections are inherent in the fabrication process. Molecular dynamics (MD) simulations, conducted using the large-scale atomic/molecular massively parallel simulator (LAMMPS) tool, were utilized to analyze the nanocutting behavior of polycrystalline γ -TiAl. The effects of cutting velocity, depth, defect size and spatial configuration were explored, focusing on cutting forces, heat generation, stress distribution, material deformation, atomic rearrangements and dislocation dynamics. The results demonstrate that defects at grain boundaries reduce cutting forces. For instance, a defect radius of 4 Å caused the cutting force in the X [100] direction to be 10% higher in the grain defect model compared to the boundary defect model. Cutting temperature increased with both speed and depth, with higher speeds leading to pronounced chip stretching and an initially expanding, then contracting, shear zone. Doubling the cutting depth from 20 Å to 40 Å doubled the shear zone's width. Cutting speed was found to significantly influence atomic structural changes, with contrasting trends in FCC and amorphous structures and a 20% increase in BCC atoms at 125 m/s compared to 75 m/s. An increase in defect radius from 2 Å to 8 Å halved the reduction rate of 1/6 〈 1 1 2 〉 (Shockley) dislocations in the grain boundary model compared to the grain defect model, which inversely correlated with dislocation density. This study employs molecular dynamics simulations to investigate the nanocutting behavior of polycrystalline γ-TiAl alloys containing spherical defects. The effects of cutting speed, depth, and defect size on cutting forces, temperature, stress distribution, atomic structure, and dislocation evolution are systematically analyzed. Results show that defect position significantly alters cutting responses, providing insights for optimizing machining processes of γ-TiAl alloys in aerospace applications. [ABSTRACT FROM AUTHOR]