Molecular dynamics simulation of nanoscale cutting mechanisms in single-crystal nickel-based superalloys with various crystal orientations

Abstract

This study employs molecular dynamics simulations to investigate the nanoscale cutting behavior and dislocation evolution of single-crystal nickel-based superalloys under various crystallographic orientations and cutting conditions. The analysis focuses on shear strain, stress distribution, atomic structure transformation, and dislocation dynamics throughout the cutting process. The key results reveal distinct orientation-dependent behaviors. Under a 30° rotation about the X-axis (X30), increasing the cutting depth leads to a reduction in localized shear strain, while stress distribution exhibits pronounced regional patterns and the emergence of periodic twin boundaries. In the case of a 45° rotation (X45), the shear strain concentration reaches its peak, accompanied by depth- and orientation-dependent transformations of twin boundaries. For the 90° rotation (X90), cutting depth exerts a significant influence on both stress and shear strain distributions. Structurally, the X30 orientation is characterized by twin boundaries containing amorphous atoms. At X45, hexagonal close-packed (HCP) atomic layers initially form, with their extent varying according to the cutting depth. In the X90 configuration, both amorphous and body-centered cubic (BCC) atomic structures are markedly increased at a depth of 20 Å. Dislocation analysis further reveals orientation-specific trends. The X30 case features various non-standard dislocations whose densities change with cutting length. At X90, distinct dislocation types such as 1/2 < 110 > and 1/6 < 112 > emerge at specific depths, while other dislocation densities remain relatively low.