A multiscale-indentation study of deformation and fracture in 6H polycrystalline silicon carbide

The mechanical behaviour of a polycrystalline silicon carbide across length scales was studied using Vickers indentation, focusing on the hardness, fracture toughness and failure mechanism of the material. For macroscopic and microscopic indentations, the hardness decreased with an increase in load, which was associated with the well-known indentation size effect as well as the internal flaws. For nanoindentation, severe plastic deformation was discovered beneath the imprints on the basal plane (0001) which is the most favourable crystallographic plane for dislocation movement. Alternative sources of plastic deformation, including deformation twinning and stacking faults, were found for nanoindentations with an increased load. Also, cracking was observed for indents made at 100 mN and above, which was used to study the fracture toughness.