The effects of atomic arrangements on mechanical properties of 2H, 3C, 4H and 6H-SiC

Abstract

As a typical polytypic compound, silicon carbide has various atomic arrangements; however, the role of atomic arrangements in the plastic deformation mechanisms remains unclear. In this article, the relationship between atomic arrangements and mechanical properties in single crystal and polycrystalline SiC is revealed by first-principle calculations and molecular dynamics simulations. We found that the twin boundary can delay the fracture of the single crystal 6H-SiC chemical bonds, could account for its excellent tensile toughness. The plastic deformation of polycrystalline SiC is dominated by dislocation nucleation and propagation under compressive strain, and by intergranular fracture under tensile strain. In addition, when the temperature exceeds 1200 K, the yield stress of polycrystalline SiC gradually stabilizes. Hexagonal SiC (2H, 4H and 6H) have stronger strain resistance than cubic one (3C) due to the hierarchical resistance of twinning and stacking fault structures to external stress. These results can provide insight into the relationship between atomic arrangements and stress response in SiC materials.