Atomic insight into the speed effect on deformation mechanisms in nano-scratching of monocrystalline iron

Ultra-high-speed machining offers significant potential to enhance material removal efficiency and reduce subsurface damage in metals. However, the interplay between machining temperature and speed on dislocation evolution and subsurface damage remains inadequately understood. This study employs molecular dynamics simulations to investigate surface and subsurface deformation mechanisms in iron across various machining speeds. Results indicate that increased machining speed improves material removal efficiency. The high strain zone concentrates near the machined surface and decreases with depth, while higher machining speeds further confine shear strain to a smaller region. Specifically, the decreased dislocation length at high machining speed indicates a deformation mechanism shift dominated by the strain rate effect. Additionally, subsurface damage depth decreases with higher speeds due to reduced shear strain penetration and enhanced stress relaxation. These findings contribute to the development of low-damage machining techniques for iron and other difficult-to-machine metals within a wide speed range.