Surface deformation, phase transition and dislocation mechanisms of single crystalline 6H-SiC in oblique nano-cutting

Abstract

Compared with the conventional orthogonal cutting, the oblique nano-cutting of 6H-SiC by tilting the tool at different angles, i.e., the tool inclination angle, is systematically investigated via molecular dynamics (MD) simulations. Focusing on the deformation mechanism, surface deformation including elastic recovery and deformation layer thickness is studied considering the edge ovalization effect in the cutting plane of oblique cutting. Moreover, the variation of cutting force is also analyzed, which relates to the improvement of processing accuracy and the structural phase transition. In particular, the transition path is clarified by coordination number analysis and virtual X-ray diffraction, which shows that the amorphization process is achieved via an initial transformation from the wurtzite structure to a fivefold coordinated orthorhombic intermediate structure, and then to an amorphous phase. Finally, dislocation analysis reveals that the basal dislocation systems dominate the dislocation behaviors, while in oblique nano-cutting especially at the tool inclination angle of 30°, the dislocation system of {0001}<11¯00> (i.e., the basal 1/3<11¯00> Shockley partial dislocation of 6H-SiC) is more activated due to the inclined-cutting-edge-derived shear stress. Furthermore, stacking faults are also formed beneath the bottom of cutting grooves due to the slip upon fivefold coordinated atoms plane.