Grain boundary traction signatures: Quantifying the asymmetrical dislocation emission processes under tension and compression

Ruizhi Li, Huck Beng Chew

Research output: Contribution to journalArticlepeer-review

Abstract

The disruption in crystallographic arrangement of atoms across a grain boundary interface generates local stress fields in the vicinity. Here, we reconstruct the continuum-equivalent grain boundary tractions from local atomic stresses near symmetrical-tilt 〈110〉 Ni grain boundaries. We show that the resolved shear stress contribution from the grain boundary tractions, τGB, along active slip-systems either assists or prevents the emission of dislocations, depending on its direction with respect to the resolved shear stress contribution from external loading, τext. When τGB acts in the same direction as τext, Shockley partial dislocations are readily emitted from the boundary once |τGBext| exceeds the critical barrier stress for shear-slip. When τGB opposes τext, the higher sustainable stresses in the grain boundary structure instead triggers: (a) emission of dislocations from the bulk, or (b) reconfiguration of the grain boundary atomic structure and subsequent emission of non-Schmid dislocations or formation of extrinsic stacking faults. Our results quantitatively explain the asymmetrical grain boundary dislocation emission processes observed in molecular dynamics (MD) simulations under applied tensile and compressive loads. The relationship between the traction signatures and periodic structural units along the grain boundary is discussed.

Original languageEnglish (US)
Pages (from-to)142-154
Number of pages13
JournalJournal of the Mechanics and Physics of Solids
Volume103
DOIs
StatePublished - Jun 1 2017

Keywords

  • Dislocation emission
  • Grain boundary tractions
  • Molecular dynamics
  • Nanocrystalline metals
  • Tension-compression asymmetry

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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