Flow strength limit of nanocrystalline tantalum predicted with molecular dynamics simulations

Cheng Huang, Xianghe Peng, Yinbo Zhao, Shayuan Weng, Bo Yang, Tao Fu

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

The effects of grain size (d) on the flow strength (σflow) as well as the deformation mechanism of nanocrystalline tantalum (NC-Ta) under uniaxial tension were investigated with molecular dynamics (MD) simulations. It showed that there exists a critical grain size of dcr = 7 nm, at which σflow reaches the maximum. Generalized stacking fault energy curves suggest that <111>{110} and <111>{112} are the easiest slip systems for dislocations and twins to occur, and after that the other slip systems might be activated. The twinning mechanism of Ta crystal is analyzed to understand the plastic deformation. For the sample with d > 7 nm, the variation of σflow against d follows the Hall-Petch relationship, attributed to the strengthening due to the accumulations of dislocations and twins with the decrease of d. For the sample with d < 7 nm, the variation of σflow against d exhibits an inverse Hall-Petch relationship, attributed to the softening induced by grain boundary activities. Additionally, cracks can be found in the samples with larger d, but they do not significantly propagate and affect the flow stress. Our simulation results could be beneficial to the design and optimization of such kind of high-performance nano-structured materials.

Original languageEnglish
Pages (from-to)1-9
Number of pages9
JournalMaterials Science and Engineering A
Volume738
DOIs
Publication statusPublished - 2018 Dec 19
Externally publishedYes

Keywords

  • Flow strength
  • Molecular dynamics
  • Nanocrystalline Ta
  • Plasticity
  • Size effect

ASJC Scopus subject areas

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

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