Influence of Competition between Intragranular Dislocation Nucleation and Intergranular Slip Transfer on Mechanical Properties of Ultrafine-Grained Metals

Abstract

Huge-scale atomistic simulations of shear deformation tests to the aluminum polycrystalline thin film containing the FrankRead source are performed to elucidate the relationship between the inter-and intragranular plastic deformation processes and the mechanical properties of ultrafine-grained metals. Two-types of polycrystalline models, which consist of several grain boundaries reproducing easy and hard slip transfer, respectively, are prepared to investigate the effect of grain boundary on flow stress. While the first plastic deformation occurs by the dislocation bow-out motion within the grain region for both models, the subsequent plastic deformation is strongly influenced by the resistance of the slip transfer by dislocation transmission through grain boundaries. The influence of the competition between the intragranular dislocation nucleation and intergranular slip transfer on the material strength is considered. The nanostructured material's strength depending on local defect structures associated with grain size and dislocation source length is assessed quantitatively.

Dislocation Multiplication from the Frank–Read Source in Atomic Models

“…These results suggest that no perfect dislocation bow-out motion occurred when applying the model by de Koning. This unexpected phenomenon has also been reported by Li et al 20) and Tsuru et al 11) To obtain strong pinning points, cylindrical holes with a diameter of 1 nm are introduced by removing the dislocation core structure on the {112} planes. The dislocation segments on the {111} planes are thus terminated by the free surfaces of the cylindrical holes.…”

A predictive model for transferability of plastic deformation through grain boundaries

“…The length of the dislocation source is 10 nm and the FR source is placed in the slip system with the maximum Schmid factor in the present study. As the critical shear stress calculated in atomistic simulation agreed well with the result for the Orowan model, 27 the FR source introduced in the present bicrystal model is expected to bow out appropriately under an applied loading. Two bicrystal models with an FR source on one side of a grain and on each side were prepared to investigate the initial yield event of each type of GB structure.…”

Heterogeneous plastic deformation and Bauschinger effect in ultrafine-grained metals: atomistic simulations

“…The interaction of dislocations with GBs is supposed to be the central factor of the inelastic behavior, anisotropic plasticity and BE of UFG metals. Atomic models have been successfully used to reconstruct specific GB structures such as coincidence site lattice GB, and a number of atomistic simulations based on molecular dynamics (MD) have been performed to investigate nanoscale plastic deformation [26,27]. Bauschinger effects of nanoscale materials were treated using MD simulation [28][29][30].…”