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Paraequilibrium and other Restricted Equilibria

Published online by Cambridge University Press:  15 February 2011

Mats Hillert
Mats Hillert*
Affiliation:
Div. of Physical Metallurgy, Royal Inst. of Technology, S-10044 Stockholm, Sweden
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Abstract

After a review of the historic development of the concept of paraequilibrium in the field of alloyed steels, the basic principles of restricted thermodynamic equilibrium at a migrating interface during phase transformations are outlined. As a demonstration they are first applied to classical nucleation. In addition to the case of paraequilibrium they are then applied to adiabatic and to isochoric conditions. It is argued that a full equilibrium model, with a spike of the intensive property in front of the migrating interface may be more realistic. It is shown that the full equilibrium conditions require about twice as much undercooling or underpressure as the restricted equilibrium conditions because of the consumption of driving force in the spike. The concept of restricted equilibrium only applies to heterogeneous phase transformations. For homogeneous reactions, the same experimental conditions will give full equilibrium.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 19: Symposium E – Alloy Phase Diagrams , 1982 , 295
Copyright
Copyright © Materials Research Society 1983

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References

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