A cooperative nano-grain rotation and grain-boundary migration mechanism for enhanced dislocation emission and tensile ductility in nanocrystalline materials

Chunhui Liu, Wenjun Lu, George Weng, Jianjun Li

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Extensive experiments and molecular dynamics simulations have shown that stress-driven grain growth can greatly contribute to enhanced dislocation emission and tensile ductility in nanocrystalline metals. However, the underlying mechanism behind this correlation remains unclear. In this work a theoretical model based on the cooperative nano-grain rotation and grain-boundary migration for grain growth is proposed to explain the enhanced dislocation emission from grain boundaries. Two partial dislocation dipoles are taken to emit from opposite grain boundaries. It is demonstrated that the joint, coupled growth behavior can indeed be achieved. The energetic characteristics and the critical stress of the emission process are analyzed. We found that under some circumstances dislocation emission is energetically unfavorable when pure nano-grain rotation or migration is operating. However, the dislocation emission process can be turned to become energetically favorable when their cooperative grain growth dominates the deformation. Moreover, the critical stress required to initiate the emission can be considerably reduced by enhancing the level of rotation, and minimized by tuning the coupling factor of the migration process. As a result, the cooperative grain growth by nano-grain rotation and grain-boundary migration can serve as a new route to enhanced dislocation emission and improved tensile ductility in nanocrystalline materials.

Original languageEnglish (US)
Pages (from-to)284-290
Number of pages7
JournalMaterials Science and Engineering A
Volume756
DOIs
StatePublished - May 22 2019

Fingerprint

Nanocrystalline materials
ductility
Dislocations (crystals)
Grain growth
Ductility
nanocrystals
Grain boundaries
grain boundaries
critical loading
Molecular dynamics
Tuning
Metals
Computer simulation
tuning
routes
dipoles
molecular dynamics
Experiments
metals

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Keywords

  • Dislocation emission
  • Grain growth
  • Nano-grain rotation
  • Nanocrystalline materials
  • Shear-coupled migration of grain boundaries

Cite this

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title = "A cooperative nano-grain rotation and grain-boundary migration mechanism for enhanced dislocation emission and tensile ductility in nanocrystalline materials",
abstract = "Extensive experiments and molecular dynamics simulations have shown that stress-driven grain growth can greatly contribute to enhanced dislocation emission and tensile ductility in nanocrystalline metals. However, the underlying mechanism behind this correlation remains unclear. In this work a theoretical model based on the cooperative nano-grain rotation and grain-boundary migration for grain growth is proposed to explain the enhanced dislocation emission from grain boundaries. Two partial dislocation dipoles are taken to emit from opposite grain boundaries. It is demonstrated that the joint, coupled growth behavior can indeed be achieved. The energetic characteristics and the critical stress of the emission process are analyzed. We found that under some circumstances dislocation emission is energetically unfavorable when pure nano-grain rotation or migration is operating. However, the dislocation emission process can be turned to become energetically favorable when their cooperative grain growth dominates the deformation. Moreover, the critical stress required to initiate the emission can be considerably reduced by enhancing the level of rotation, and minimized by tuning the coupling factor of the migration process. As a result, the cooperative grain growth by nano-grain rotation and grain-boundary migration can serve as a new route to enhanced dislocation emission and improved tensile ductility in nanocrystalline materials.",
keywords = "Dislocation emission, Grain growth, Nano-grain rotation, Nanocrystalline materials, Shear-coupled migration of grain boundaries",
author = "Chunhui Liu and Wenjun Lu and George Weng and Jianjun Li",
year = "2019",
month = "5",
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doi = "10.1016/j.msea.2019.04.055",
language = "English (US)",
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TY - JOUR

T1 - A cooperative nano-grain rotation and grain-boundary migration mechanism for enhanced dislocation emission and tensile ductility in nanocrystalline materials

AU - Liu, Chunhui

AU - Lu, Wenjun

AU - Weng, George

AU - Li, Jianjun

PY - 2019/5/22

Y1 - 2019/5/22

N2 - Extensive experiments and molecular dynamics simulations have shown that stress-driven grain growth can greatly contribute to enhanced dislocation emission and tensile ductility in nanocrystalline metals. However, the underlying mechanism behind this correlation remains unclear. In this work a theoretical model based on the cooperative nano-grain rotation and grain-boundary migration for grain growth is proposed to explain the enhanced dislocation emission from grain boundaries. Two partial dislocation dipoles are taken to emit from opposite grain boundaries. It is demonstrated that the joint, coupled growth behavior can indeed be achieved. The energetic characteristics and the critical stress of the emission process are analyzed. We found that under some circumstances dislocation emission is energetically unfavorable when pure nano-grain rotation or migration is operating. However, the dislocation emission process can be turned to become energetically favorable when their cooperative grain growth dominates the deformation. Moreover, the critical stress required to initiate the emission can be considerably reduced by enhancing the level of rotation, and minimized by tuning the coupling factor of the migration process. As a result, the cooperative grain growth by nano-grain rotation and grain-boundary migration can serve as a new route to enhanced dislocation emission and improved tensile ductility in nanocrystalline materials.

AB - Extensive experiments and molecular dynamics simulations have shown that stress-driven grain growth can greatly contribute to enhanced dislocation emission and tensile ductility in nanocrystalline metals. However, the underlying mechanism behind this correlation remains unclear. In this work a theoretical model based on the cooperative nano-grain rotation and grain-boundary migration for grain growth is proposed to explain the enhanced dislocation emission from grain boundaries. Two partial dislocation dipoles are taken to emit from opposite grain boundaries. It is demonstrated that the joint, coupled growth behavior can indeed be achieved. The energetic characteristics and the critical stress of the emission process are analyzed. We found that under some circumstances dislocation emission is energetically unfavorable when pure nano-grain rotation or migration is operating. However, the dislocation emission process can be turned to become energetically favorable when their cooperative grain growth dominates the deformation. Moreover, the critical stress required to initiate the emission can be considerably reduced by enhancing the level of rotation, and minimized by tuning the coupling factor of the migration process. As a result, the cooperative grain growth by nano-grain rotation and grain-boundary migration can serve as a new route to enhanced dislocation emission and improved tensile ductility in nanocrystalline materials.

KW - Dislocation emission

KW - Grain growth

KW - Nano-grain rotation

KW - Nanocrystalline materials

KW - Shear-coupled migration of grain boundaries

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