Theoretical Investigation of Nonequilibrium Grain Boundary Diffusion Properties

  1. Prof. Dr. Michael Zehetbauer2 and
  2. Prof. Ruslan Z. Valiev3
  1. V. N. Perevezentsev

Published Online: 28 JAN 2005

DOI: 10.1002/3527602461.ch14c

Nanomaterials by Severe Plastic Deformation

Nanomaterials by Severe Plastic Deformation

How to Cite

Perevezentsev, V. N. (2004) Theoretical Investigation of Nonequilibrium Grain Boundary Diffusion Properties, in Nanomaterials by Severe Plastic Deformation (eds M. Zehetbauer and R. Z. Valiev), Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, FRG. doi: 10.1002/3527602461.ch14c

Editor Information

  1. 2

    Institut für Materialphysik, Universität Wien, Boltzmanngasse 5, 1090 Wien, Austria

  2. 3

    Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, 12 K. Marks Str., Ufa, 450 000, Russia

Author Information

  1. Blagonravov Nizhni Novgorod Branch of Mechanical Engineering Research Institute, Russian Academy of Sciences, Nizhny Novgorod, Russia

Publication History

  1. Published Online: 28 JAN 2005
  2. Published Print: 25 FEB 2004

ISBN Information

Print ISBN: 9783527306596

Online ISBN: 9783527602469

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Keywords:

  • nonequilibrium grain boundary diffusion properties;
  • theoretical investigation;
  • delocalised;
  • selfdiffusion;
  • heterodiffusion;
  • NMC diffusion

Summary

Despite of a number of works devoted to the theory of grain boundary (GB) diffusion, the mechanisms of diffusion in general GBs (i.e., in boundaries with a disordered atomic structure [1]) are open to discussion [2,3]. Theoretical models based on the concept of the mechanism of diffusion as a motion of localized GB vacancies contradict the results of computer simulation of GB atomic structure. According to these calculations, a vacancy in a general GB is unstable and is delocalised as a result of atoms relaxational displacements [4–5]. In recent years, interest in this problem increased because of anomalously high coefficients of diffusion along GBs were revealed in submicrocrystalline materials obtained by severe plastic deformation [6]. It has been shown [7–9] that coefficients of self- and heterodiffusion in such materials may be one order of magnitude (or even more) higher than in the coarse-grain state. These anomalies of NMC diffusion are assumed to be associated with the nonequilibrium structure of GBs [4].

In this paper, we consider a new mechanism of selfdiffusion in GBs with a disordered atomic structure. This mechanism is based on the concept of metastable vacancies arising as a result of thermal fluctuations of density and disappearing upon subsequent relaxational rearrangement of the atomic structure of the GB.