A Study on Material Removal Caused by Phase Transformation of Monocrystalline Silicon During Nanocutting Process via Molecular Dynamics Simulation

A series of molecular dynamics (MD) simulations are carried out to investigate the material removal mechanism of monocrystalline silicon with a diamond tool in nanocutting process. Tersoff potential is employed to describe the interactions between silicon atoms, and the interactions between silicon and carbon atoms are modeled by Morse potential. Simulation result indicates that during the nanocutting process, the silicon atoms in the chip formation zone undergo phase transformation. The amorphization results in plastic deformation and defects in the machining zone, constituting the deformation condition for ductile-mode cutting. Stress analysis proves that compressive stress suppresses crack formation but contributes to forming continuous plastic flow, and the continuous plastic flow in the amorphous phase region causes ductile-mode cutting. On the contrary, high tensile stress is beneficial for defects to enlarge to crack after the peak deformation zone passes by, and the crack is essential for brittle-mode cutting. So in order to get high surface finish quality and improve the machinability of monocrystalline silicon or other brittle semiconductor materials, the material should be removed in ductile-mode. By the simulation results reveal that extremely small cutting depth, large cutting edge radius, and negative rake angle are beneficial to removal in ductile-mode.