Investigation on the microstructure evolution and nanocutting mechanism of single-crystal copper under different crystal orientations

In order to investigate the microstructure evolution of single-crystal copper (SCC) subjected to nanocutting process under different crystal orientations, SCC with crystal oriented (0 0 1) [0 (1) over bar 0] is rotated around X and Y axes by 30 degrees, 45 degrees, and 60 degrees, respectively. A nanocutting model is built based on large-scale atomic/molecular massively parallel simulator (LAMMPS), and molecular dynamics simulation (MDS) is used to test how the microstructure of SCC changes when subjected to nanocutting process under different crystal orientations, assuming EAM potential between Cu atoms and Morse potential between Cu atoms and the tool. The results show that the crystal orientation indicates a remarkable difference in chip morphology and cutting surface: under crystal orientation of rotating around X-axis, the chips are far wider and thicker than those under crystal orientation of rotating around Z-axis in all cases tested; under crystal orientation of rotating around X-axis, a sudden jump is detected on the cutting surface, whereas no such phenomenon is observed under crystal orientation of rotating around Z-axis. Crystal orientation also makes a marked difference to shear stress and dislocation form: under crystal orientation of rotating around X-axis, the shear stress is higher than that under crystal orientation of rotating around Z-axis; under crystal orientation of rotating around X-axis, the dislocation degree and maximum length of the dislocation line are obviously negatively correlated to the rotation angle. HCP atoms display roughly the same evolution as amorphous atoms; FCC atoms show a completely opposite profile to HCP atoms. The effect of crystal orientation on dislocation density also varies considerably across different types of dislocation.