Gradient nanocrystalline SiC design: Grain boundary-mediated deformation mechanisms and sensitivity of gradient direction

MY Shao and C Xu and RH Hu and Z Lang and PW Li and ZX Wang and HP Liu and CM Liu, SURFACES AND INTERFACES, 73, 107505 (2025).

DOI: 10.1016/j.surfin.2025.107505

Although the potential advantages of gradient nanocrystalline (GNC) materials have been partially proposed, the research on the impact response of SiC is still relatively limited. To this end, this study systematically explored the mechanical response and plastic deformation mechanism of two typical GNC-SiC, i.e. positive gradient (PG) and negative gradient (NG) SiC, under 2 km/s impact loading based on molecular dynamics simulation and compared them with uniform-grain-sized (UGS) SiC samples. The results show that the grain boundary (GB) density and grain size significantly affect the structural stability and impact response behavior of the material, among which the gradient structure shows excellent shear resistance, and NG-SiC is superior to PG-SiC in overall stability and deformation resistance. Further analysis reveals that the plastic deformation in the gradient structure is mainly driven by GB-mediated mechanisms (such as sliding and migration) and deformation twinning, which effectively alleviates local stress concentration and delays structural damage. In addition, SiC demonstrates a pronounced sensitivity to the directionality of the gradient configuration, highlighting the significant potential of microstructural design in tailoring its mechanical response. The findings of this study provide new ideas for understanding the microscopic response mechanism of nanoceramics under extreme dynamic loads and provide a theoretical basis and design reference for constructing advanced structural ceramic materials with high impact resistance and structural integrity.

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