Journal of Materials Science

, Volume 17, Issue 7, pp 2127–2132 | Cite as

Some geometrical aspects of microstructural stability

  • G. W. Greenwood
Papers

Abstract

Microstructural instability commonly arises from a progressive decrease in interfacial area and thus in free energy. Particle coarsening processes provide an example of this but most of the work on microstructural instability has concentrated attention on particles within grains and at grain boundary surfaces. Despite the fact that the geometrical principles are well documented and understood, little consideration has been given to the coarsening processes of particles at grain edges and grain corners beyond the general recognition that such sites present favourable situations for preferential growth. It is noted here that certain specific features arise for particular values of the ratio between the interfacial and grain-boundary energies. Within a specific range of values of this ratio which are not very common in practice, there is a possibility of preferential growth of particles at grain corners and their stabilization independently of their initial size. More particularly and over a wider range of this ratio, a gross change in particle morphology, effectively as a spreading as a second phase along grain edges, can occur with the special characteristics that there is an advantage to such spreading with a small cross-section perpendicular to the grain edge at the expense of some reduction in the cross-section of a thicker section of material spread along a neighbouring grain edge. From these considerations, it is suggested that a particularly stable form of microstructure may be developed which could conceivably form a good basis for fibre reinforcement.

Keywords

Free Energy Interfacial Area Particle Coarsening Thick Section Progressive Decrease 

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References

  1. 1.
    C. S. Smith, Met. Rev. 9 (1964) 1.Google Scholar
  2. 2.
    J. W. Christian, “The Theory of Transformations in Metals and Alloys” (Pergamon Press, Oxford, 1965).Google Scholar
  3. 3.
    G. A. Chadwick, “Metallography of Phase Transformations” (Butterworths, London, 1972).Google Scholar
  4. 4.
    J. W. Martin and R. D. Doherty, “Stability of Microstructure in Metallic Systems” (Cambridge University Press, London, 1976).Google Scholar
  5. 5.
    H. Mykura, “Solid Surfaces and Interfaces” (Dover Publications, New York, 1966) p. 31.Google Scholar
  6. 6.
    R. Eborall and P. Gregory, J. Inst. Met. 84 (1955–6) 88.Google Scholar
  7. 7.
    R. E. Williams, Science 161 (1968) 276.Google Scholar
  8. 8.
    W. T. Kelvin, Phil Mag. 24 (1887) 503.Google Scholar
  9. 9.
    S. P. Tucker and F. G. Hochgraf, Metallog. 6 (1973) 457.Google Scholar
  10. 10.
    W. Beere, Acta Metall. 23 (1975) 131.Google Scholar
  11. 11.
    M. O. Tucker and J. A. Turnbull, Proc. Roy. Soc. A343 (1975) 299.Google Scholar
  12. 12.
    M. O. Tucker, J. Nucl. Mater. 79 (1979) 206.Google Scholar
  13. 13.
    G. W. Greenwood, “The Mechanism of Phase Transformations in Solids” Report Series No. 33 (Institute of Metals, London, 1969) p. 103.Google Scholar
  14. 14.
    P. J. Wray, Acta Metall. 24 (1976) 125.Google Scholar
  15. 15.
    A. Kelly, “Strong Solids” (Clarendon Press, Oxford, 1966).Google Scholar

Copyright information

© Chapman and Hall Ltd 1982

Authors and Affiliations

  • G. W. Greenwood
    • 1
  1. 1.Department of MetallurgyUniversity of SheffieldSheffieldUK

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