Generation of Nanocracks at Deformation Twins in Nanomaterials

The formation of cracks at nanoscale deformation twins stopped by grain boundaries (GBs) is theoretically described as a new fracture mode in nanocrystalline and ultrafine-grained materials. It is noted that dipoles of partial wedge disclinations are formed at GBs, where they stop deformation twins and create high local stresses capable of initiating crack generation. Within this scenario, the critical parameters for crack generation at deformation twins stopped by GBs are revealed. The results of the theoretical analysis explain the corresponding data of experiments and computer simulations and predict novel specific features of the crack formation in deformed nanomaterials.