On the hierarchy of deformation processes in nanocrystalline alloys: Grain boundary mediated plasticity vs. dislocation slip

Hybrid molecular dynamics and Monte-Carlo simulations on the deformation behavior of nanocrystalline Pd-Au are presented. A semi-grandcanonical Monte-Carlo scheme is employed during straining to allow for local relaxation by chemical equilibration and to effectively shortcut diffusional processes. Altering the balance between an imposed straining and local relaxation reveals a strong correlation of the irreversible plastic deformation and the frequency of local relaxation. Using a novel method to quantify the amount of crystal slip strain from atomistic data, it is demonstrated how plastic deformation carried by dislocations changes as a function of the local relaxation. The results indicate that conventional molecular dynamics simulations overestimate the contributions of dislocation slip to the overall plastic deformation of nanocrystalline samples. (C) 2013 AIP Publishing LLC.