| A theoretical model is suggested that describes the role of amorphous intergranular boundaries as toughening elements in deformed nanocrystalline ceramics. Within the model, immobile lattice dislocations are generated at amorphous intergranular boundaries (through local shear events) under external stress concentrated near crack tips. The dislocations cause a partial stress relaxation in vicinities of crack tips and thereby enhance fracture toughness. It is shown that the dislocation generation is energetically favorable and effective in toughness enhancement in nanocrystalline SiC with amorphous intergranular boundaries. |
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