Effect of nanograin boundary sliding on nanovoid growth by dislocation shear loop emission in nanocrystalline materials

• Suggest a theoretical model to describe effect of NGB sliding on nanovoid growth.
• Derive analytical expression of critical stress for the first dislocation emission.
• Nanovoid growth is slowed down or even arrested due to NGB sliding deformation.
• Effect of NGB sliding deformation on critical stress is evaluated.
• Effect of sizes of nanograin and nanovoid on critical stress is studied.

A theoretical model is suggested to describe the effect of nanograin boundary (NGB) sliding at triple junctions of grain boundaries on nanovoid growth by incipient emission of dislocation shear loop from its surface in mechanically loaded nanocrystalline materials. In the framework of the model, NGB sliding deformation represents generation of disclination dipoles at triple junctions of NGBs. The analytical expression of critical stress for the first dislocation emission is derived. The effects of NGB sliding deformation, the sizes of nanograin and nanovoid on critical stress and the corresponding most favorable slip plane for dislocation emission are evaluated quantitatively in the deformed nanocrystalline materials. The results indicate that NGB sliding deformation releases, in part, the high stresses near the nanovoid, thereby nanovoid growth is slowed down or even arrested with the increment of the strength of NGB sliding deformation in nanocrystalline solids. There exists a range of nanovoid size to make critical stress keep almost unchanged with the appearance of NGB sliding deformation. There is also a critical nanograin size to make critical stress reach the maximum value, at which dislocation emission and nanovoid growth occur most difficultly.