A multi-scale approach was used in which the results of atomistic simulations were combined with discrete dislocation dynamics simulations of crack-tip plasticity. The method was used to study the effects of dislocation blocking upon the fracture behavior of α-Fe and Al. The effects of blocking were studied for distances ranging from 5nm to 1mm, and it was found that the fracture resistance increased with increasing blocking distance. The atomistic and dislocation dynamics simulations showed that the blocking of dislocations caused a net decrease in the shear stress projected onto the slip plane; preventing further dislocation emission. Semi-brittle cleavage occurred after a certain number of dislocations were emitted, explicitly demonstrating the embrittling effects of dislocation blocking. This effect could contribute to the brittle behavior which was observed in some nanocrystalline metals.

Effect of Dislocation Blocking on Fracture Behavior of Al and α-Fe - a Multi-Scale Study. S.J.Noronha, D.Farkas: Materials Science and Engineering A, 2004, 365[1-2], 156-65