Single crystal silicon carbide (SiC) is widely used for optoelectronics applications. Due to the anisotropic characteristics of single crystal materials, the C face and Si face of single crystal SiC have different physical properties, which may fit for particular application purposes. This paper presents an investigation of the material removal and associated subsurface defects in a set of scratching tests on the C face and Si face of 4H-SiC and 6H-SiC materials using molecular dynamics simulations. The investigation reveals that the sample material deformation consists of plastic, amorphous transformations and dislocation slips that may be prone to brittle split. The results showed that the material removal at the C face is more effective with less amorphous deformation than that at the Si face. Such a phenomenon in scratching relates to the dislocations on the basal plane (0001) of the SiC crystal. Subsurface defects were reduced by applying scratching cut depths equal to integer multiples of a half molecular lattice thickness, which formed a foundation for selecting machining control parameters for the best surface quality.

This paper investigates the influence of different abrasive morphology of silicon carbide (SiC) through molecular dynamics simulations on the scratching process, aiming to provide theoretical guidance and process optimization directions for the precision machining of SiC materials. The paper analyzes the differences in contact area, stress distribution, and material deformation mechanisms between sphere, cone, frustum cone, face of a square pyramid and edge of a square pyramid abrasives during the scratching process. It focuses on key characteristics such as scratching force, atom removal, surface topography, amorphous deformation, and subsurface stress distribution. The results show that the morphology of the abrasive significantly affects machining efficiency and surface quality, with sphere abrasives being more prone to plastic deformation and pyramid abrasives tending to cause brittle fracture. Additionally, the interaction between abrasive morphology and SiC crystal orientation also has a significant impact on the scratching process. This paper not only reveals the surface formation mechanisms of SiC under different abrasive morphology but also provides important theoretical and experimental basis for achieving more efficient and precise SiC material machining.

This research adopts molecular dynamics simulations to investigate the scratches on titanium alloys under varying laser intensities, focusing on microscopic characteristics such as tangential forces, material removal, subsurface deformation, and phase transition. The results indicate that the local energy input generated by laser irradiation leads to an increase in temperature in the irradiated area, and the increase in atomic thermal energy reduces the stability of interatomic interactions, resulting in a decrease in the stability of the local lattice structure. The thermal softening effect reduces material hardness, significantly enhancing the material removal rates and subsurface material integrity. If the laser intensities are set as the range from 5 × 10 ⁸ W cm ⁻² to 7 × 10 ⁸ W cm ⁻² , both the phase transition and amorphous deformation are at a lower level. Under relatively high laser intensity conditions, the triangular amorphous rings disappear because stronger thermal softening promotes atomic rearrangement and inhibits the formation of the local amorphous structures. However, excessive laser thermal input may introduce additional subsurface damage. In contrast, when the laser intensity ranges between 5 × 10 ⁸ and 7 × 10 ⁸ W cm ⁻² , a balance can be achieved between thermal softening and structural stability, thereby reducing the degree of phase transformation and amorphization, while also decreasing the size and number of triangular amorphous rings to some extent. These findings elucidate the material removal and subsurface damage mechanisms of titanium alloys under laser radiation at the nanoscale, providing theoretical basis and machining guidance for achieving ultra precision machining of titanium alloys.