Special strain hardening mechanism and nanocrack generation in nanocrystalline materials

A special mechanism of strain hardening in deformed nanocrystalline materials (NCMs) is suggested and theoretically described. The mechanism represents generation of disclination dipoles at grain boundaries (GBs) due to GB sliding. It is shown that special strain hardening can effectively suppress plastic flow instability in metallic and ceramic NCMs and thus enhance their ductility. At the same time, the disclination dipoles formed due to GB sliding serve as dangerous stress sources that can induce nucleation of nanocracks, decreasing ductility of NCMs. (c) 2007 American Institute of Physics.