**5. Dislocation Emission from Grain Boundaries in Nanocrystalline Materials**

Finally, utilizing the brief discussion provided in previous sections we consider the Dislocation Emission from GBs in NC materials in some detail. Rapid development of NC materials has raised the question of the role that dislocation pile-ups and other modes of dislocation production play in determining the strength of the materials, vis-a-vis the HP effect. For this purpose, we divide the region in two subsections. First, we consider deformation mechanisms, ultrafine grains, typically between 20 to 100 nm, and later grains finer than that.
