Numerical investigation on the temperature effect in nanometric cutting of polycrystalline silicon

In nanometric cutting, the deformation mechanism is significantly affected by the cutting temperature. In this paper, molecular dynamics simulation was conducted to investigate the cutting mechanism of polycrystalline silicon with increasing temperature. The surface generation, plastic deformation, and phase transition mechanism were discussed with consideration of the effect of grain boundaries and non-homogeneity of crystal orientation in workpiece. The results indicate that the surface generation and subsurface damage mechanism of polycrystalline silicon is greatly influenced by the cutting temperature. Squeeze of amorphous atoms into grain boundaries is observed at room temperature while sliding of grains becomes more apparent when the cutting temperature is increased. Besides, intra-granular and inter-granular fracture can be detected near the triple junction, leading to voids and cracks on the machined surface. Furthermore, the plastic deformation is promoted with increasing cutting temperature, and the deformation depth for polycrystalline silicon is larger than that for single-crystal silicon. Moreover, the amorphization of crystal phase in workpiece involves intra-granular and inter-granular mode. When the cutting temperature is increased, the inter-granular amorphization can be effectively promoted. In addition, the recrystallization is observed when cutting polycrystalline silicon at high temperature while the crystal purity of the machined surface is less than that in single-crystal silicon.