Insight from molecular dynamics into the temperature effect on material nanomechanical properties and damage behaviors in nano-cutting of 6H-SiC

In this study, molecular dynamics (MD) simulations were employed to systematically investigate the evolution of nanomechanical behaviors and nano-cutting deformation mechanisms of 6H-SiC under varied machining temperatures, which fills the research gap regarding the temperature-dependent evolution of nanomechanical properties and plastic removal characteristics of 6H-SiC. The results reveal that, compared with those at room temperature 300 K, the hardness at 1200 K decreases by approximately 16%, the elastic modulus drops by about 23%, and the ultimate tensile strength is also reduced. Meanwhile, the fracture mode transitions from intrinsic brittle fracture to transient strain hardening behavior. The temperature-induced degradation in hardness and tensile strength facilitates structural transformations within the chip, leading to an increased proportion of amorphous atoms and a decrease in crystalline grain size, thereby promoting a more stable material removal process. Furthermore, the weakened nanomechanical properties render the surface more susceptible to deformation under the tensile stress induced by the tool cutting edge arc and the flank face, resulting in a thicker surface deformation layer. In addition, a multi-layered diamond structures induced by atomic strain associated with 1/3〈1–100〉 dislocation motion was observed within the deformation layer at elevated temperatures. Moreover, dislocation motion shifts from basal slip along the (0001) plane at low temperatures to dislocation climb perpendicular to the basal plane at elevated temperatures, further accelerating phase transformations and plastic deformation. Overall, this study clarifies the temperature-regulated mechanism underlying the nanomechanical properties and plastic removal capability of 6H-SiC, providing a fundamental theoretical basis for achieving efficient and controllable nano-cutting of hard and brittle materials.