On the underlying micromechanisms in time-dependent anelasticity in Al-(1 wt%)Cu thin films

L.I.J.C. Bergers, J.P.M. Hoefnagels (Corresponding author), M.G.D. Geers

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

This paper reveals potential micro mechanisms underlying time-dependent anelasticity observed in Al-(1 wt%)Cu thin films. The analyzed deformation mechanisms involve dislocation motion and interaction with solute diffusion, grain boundaries and precipitates. In order to investigate the role of these mechanisms, Al-(1 wt%)Cu alloy thin films are heat treated to systematically change the precipitation state, while characterizing the grain boundary distribution with electron backscatter diffraction. Micromechanical characterization is performed by microbeam bending, nano-tensile creep testing and nano-indentation. Results in microbeam bending reveal, for all precipitate and grain boundary states considered, a similar time-dependent evolution of the anelastic strain after load release. The magnitude of the recovered strain is also observed to be independent of the precipitate or grain boundary configuration. The nano-tensile creep test also indicates the same time-dependent anelastic evolution, indicating that the loading state does not affect the underlying mechanisms. Analysis of strain bursts in nano-indentation shows that pinning of dislocations by Cu solutes is unaffected by the precipitation state. Based on uniaxial creep and time-dependent anelasticity measurements in pure Al specimens, it is made plausible that the time-dependent anelasticity originates from diffusion-limited glide or climb of dislocation segments that are pinned at Cu solutes or in dislocation structures, which provide an internal driving force.

Original languageEnglish
Pages (from-to)47-58
Number of pages12
JournalActa Materialia
Volume124
DOIs
Publication statusPublished - 1 Feb 2017

Keywords

  • Al-Cu alloy
  • Anelasticity
  • Creep
  • Micromechanical testing
  • Thin films

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