New double kink model for deformation in high temperature materials

T. E. Mitchell, J. P. Hirth, Pedro Peralta

Research output: Chapter in Book/Report/Conference proceedingChapter

1 Scopus citations

Abstract

A new double kink dislocation model is described. It explains the temperature dependence of the yield stress in materials such as oxides and intermetallics that require high temperatures for plastic flow. The major variation in the free energy for the formation of a double kink nucleus with stress is the kink-kink activation energy. However, there is also a stress dependence of the pre-exponential factor in the strain rate constitutive equation arising from kink diffusion. Numerical solution of the resulting equations shows that there are temperature regimes where the stress varies logarithmically either with temperature or with reciprocal temperature. The model explains quantitatively the temperature dependence of the critical resolved shear stress (CRSS) on different slip systems for sapphire (α-Al2O3) and spinel (MgO·nAl2O3, n≥1) in terms of different activation energies for kink diffusion on partial dislocations. The model can be modified to explain the rapid reduction in the CRSS of spinel with increasing n by incorporating enhanced kink nucleation and diffusion due to cation vacancies. This changes the activation energy and the strain-rate term and explains why the CRSS decreases as the inverse of the square of the cation vacancy concentration, as is observed.

Original languageEnglish (US)
Title of host publicationProceedings of the TMS Fall Meeting
Place of PublicationWarrendale, PA, United States
PublisherMinerals, Metals & Materials Soc (TMS)
Pages137-147
Number of pages11
StatePublished - 1999
Externally publishedYes
EventAdvanced Materials for the 21st Century: The 1999 Julia R. Weertman Symposium - Cincinnati, OH, USA
Duration: Oct 31 1999Nov 4 1999

Other

OtherAdvanced Materials for the 21st Century: The 1999 Julia R. Weertman Symposium
CityCincinnati, OH, USA
Period10/31/9911/4/99

ASJC Scopus subject areas

  • Engineering(all)

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  • Cite this

    Mitchell, T. E., Hirth, J. P., & Peralta, P. (1999). New double kink model for deformation in high temperature materials. In Proceedings of the TMS Fall Meeting (pp. 137-147). Minerals, Metals & Materials Soc (TMS).