Microplastic processes developed in pure Ag with mesoscale annealing twins

Khaled Jabr Hasan Al-Fadhalah, Chun Ming Li, Armand Joseph Beaudoin, D. A. Korzekwa, I. M. Robertson

Research output: Contribution to journalArticlepeer-review

Abstract

The impact of annealing twin boundaries with a high residual defect content on the mechanical response of polycrystalline fine- and coarse-grained (2 and 20 μm) silver was investigated through transmission electron microscopy and modeling. Besides an increase in the yield strength, the fine-grained material exhibited an inflection in the stress-strain curve after initial yield. Static and dynamic TEM studies revealed that the annealing twin boundaries acted as sources of perfect dislocations, partial dislocations and deformation twins; as barriers to the propagation of these dislocations; and as annihilation sites for dislocations. With increasing strain and as the twin boundaries were penetrated by dislocations, they contributed less to the overall mechanical properties. Based on these observations, equations for the evolution of mobile and forest dislocation densities are posed, depicting boundary sources and dislocation-dislocation interactions, respectively. The deformation response is modeled by computing the aggregate response of matrix-twin composite grains in the viscoplastic self-consistent scheme, which permits consideration of compatibility and equilibrium requirements across the twin boundaries. This work highlights the significant role boundaries play in generating the dislocations that control the macroscopic mechanical response.

Original languageEnglish (US)
Pages (from-to)5764-5774
Number of pages11
JournalActa Materialia
Volume56
Issue number19
DOIs
StatePublished - Nov 1 2008

Keywords

  • Plastic deformation
  • Silver
  • Tension test
  • Transmission electron microscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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