Molecular Dynamics Study on Drilling Performance and Cutting Behavior of Fe–Bi Free-Cutting Steel

A drilling model for Fe–Bi alloy was developed using molecular dynamics (MD) methods to investigate the effect of Bi inclusions on the cutting performance of free-cutting steels in terms of drilling force variation, atomic displacement, structural evolution, and dislocation density. The results show that Bi inclusions reduce the drilling force and temperature, and substantially decrease the impact area of the workpiece during the drilling process, resulting in fewer atomic displacements. In addition, Bi inclusions also reduce the stress and temperature range of Fe–Bi free-cutting steels. The higher the feed velocity of the drill, the smaller the number and length of dislocation lines generated in the workpiece. When the feed velocity of the drill is greater than 300 nm/fs, the number and length of dislocations in the DXA analysis of Fe–Bi workpieces decrease rapidly, while the number and length of dislocations in the pure Fe model change slightly.