| A special mechanism of stress relaxation in nanocrystalline coatings is suggested and theoretically described. The mechanism represents the local migration of interfaces, first of all, grain boundaries (GBs), that occurs in athermal way and is accompanied by formation of wedge disclination quadrupoles in nanocrystalline coatings. The wedge disclination quadrupoles release, in part, mismatch stresses created at coating/substrate boundaries. It is theoretically shown that the special relaxation mechanism is energetically favorable in such nanocrystalline coating/substrate systems as GaN/6H-SiC and AlN/6H-SiC systems in wide ranges of their parameters. |
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