Enhanced dislocation emission from grain boundaries in nanocrystalline materials

A new mechanism for enhanced dislocation emission from grain boundaries (GBs) in deformed nanocrystalline (NC) materials is suggested and theoretically described. The dislocation emission is highly enhanced by intergrain sliding (or stress-driven GB migration) and occurs in directions approximately perpendicular to GB planes, in contrast to its conventional counterpart occurring in directions approximately parallel with GBs that carry intergrain sliding. The energy and stress characteristics of the enhanced dislocation emission in NC aluminum and NC silicon carbide are calculated.