Directionality of yield point in strain-aged steels: The role of polar dislocations

V. Taupin, S. Varadhan, C. Fressengeas, A. J. Beaudoin

Research output: Contribution to journalArticlepeer-review

Abstract

The directionality of the sharp yield point in strain-aged steels has been investigated by modeling tension/compression and forward/reverse torsion tests separated by accelerated aging. The occurrence of a Bauschinger effect and the absence of a yield point after a forward straining-aging-reverse straining sequence are interpreted within the framework of a field dislocation theory coupling the evolution of statistical and polar dislocation densities with that of point defects due to strain aging. The polar dislocation density reflects lattice incompatibility and long-range internal stresses. By assisting yielding in reverse straining, the associated back-stress is seen as the origin of the Bauschinger effect. By also promoting dislocation unlocking, the back-stress is found to be responsible for the absence of a yield point in reverse straining. Polarized dislocation structures formed in forward straining in association with back-stress build up may annihilate and inverse polarization occur in reverse straining. This microstructure evolution translates into an inflexion of strain hardening after strain path reversal.

Original languageEnglish (US)
Pages (from-to)3002-3010
Number of pages9
JournalActa Materialia
Volume56
Issue number13
DOIs
StatePublished - Aug 2008

Keywords

  • Bauschinger effect
  • Dislocation structures
  • Static aging
  • Strain gradient plasticity
  • Yield point

ASJC Scopus subject areas

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

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