Nucleation of nanograins near cracks in nanocrystalline materials

Nucleation of nanograins near crack tips and its role as a special (new) toughening mechanism in deformed nanocrystalline materials are theoretically described. Within our description, stress-driven splitting and migration of grain boundaries occur near crack tips. These stress-driven processes result in nucleation of nanograins and cause a partial stress relaxation near cracks. It is shown that the nucleation of nanograins near crack tips is energetically favorable and effective in enhancing toughness in nanocrystalline ceramic α-Al2O3.