Role of layer thickness and dislocation distribution in confined layer slip in nanolaminated Nb

WR Jian and SZ Xu and YQ Su and IJ Beyerlein, INTERNATIONAL JOURNAL OF PLASTICITY, 152, 103239 (2022).

DOI: 10.1016/j.ijplas.2022.103239

Confined layer slip (CLS) is considered as the primary mechanism for plastic deformation in nanolaminates. It depicts the confined motion of a single dislocation between two parallel interfaces nanometers apart. Using atomistic simulations, we investigate the effects of interface spacing, or equivalently individual layer thickness, and dislocation distribution on the CLS of an edge dislocation in nanolaminated Nb with coherent twin boundaries and Nb nanofilm. We show that CLS motion transitions from smooth glide to staggered glide as the nanolayer thickness increases, while the line bows out, as theoretically pictured. For the same nanolayer thicknesses L, dislocation CLS in the nanofilm is smooth and the CLS resistance is 47% to 79% lower. For both the nanolaminate and film, the nanolayer size L effect on CLS resistance is found to follow the expected ln(L)/L scaling with an additional constant that depends on the interface/dislocation interaction but is independent of L. When like-signed dislocation glide concurrently on the same glide plane in the adjacent layers, the dislocations move with almost no bow- out, and the CLS resistance is substantially reduced, even below that of the thin film bounded by two free surfaces. With an increase in the glide plane separation between like-signed dislocations in the neighboring layers, a higher flow stress is obtained. However, when the dislocations are oppositely signed, CLS motion is jerky and the stress fluctuates and overall increases three fold.

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