Generation and interaction mechanisms of prismatic dislocation loops in FCC metals

Can Erel, Giacomo Po, Tamer Crosby, Nasr Ghoniem

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

We investigate the mechanisms of prismatic loop formation, motion, interactions, and large-scale patterning in fcc metals utilizing Discrete Dislocation Dynamics (DDD). We identify two main formation mechanisms; both enabled by cross-slip of screw dislocations. The first is termed Super-Jog-Drag-Truncation (SJDT), and the second is the Offset-Double-Cross-Slip (ODCS) mechanism. DDD simulations show that the ODCS mechanism is a precursor to the SJDT mechanism, which then leads to the formation of prismatic loop arrays. It is shown that successive SJDT events enable a knitting mechanism that can generate long strings of prismatic loop arrays, consistent with experiments. We show that fully sessile dislocation segments arise in several loop-loop interactions, leading to Frank-Read and single-arm type sources. A new stable butterfly configuration is found when two {11¯1}<011> prismatic loops interact to form glissile segments on conjugate glide planes, joined by one sessile segment that pins this structure. Absorption of prismatic loops by screw segments and the formation of helical turns is reproduced by DDD simulations, consistent with earlier MD results. An efficient new tripolar transport mechanism is found to contribute to the clustering of prismatic loops near Persistent Slip Band (PSB) channel walls during fatigue loading.

Original languageEnglish (US)
Pages (from-to)32-46
Number of pages15
JournalComputational Materials Science
Volume140
DOIs
StatePublished - Dec 2017
Externally publishedYes

Keywords

  • Dislocation dipoles
  • Dislocation dynamics
  • Dislocation patterning
  • Prismatic loops
  • Sessile segments

ASJC Scopus subject areas

  • Computer Science(all)
  • Chemistry(all)
  • Materials Science(all)
  • Mechanics of Materials
  • Physics and Astronomy(all)
  • Computational Mathematics

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