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Evolution of the microstructure of cobalt during diffusionless transformation cycles

Published online by Cambridge University Press:  31 January 2011

A. Munier ,
J. E. Bidaux ,
R. Schaller  and
C. Esnouf
A. Munier
Affiliation:
Institut de Génie Atomique, Ecole Polytechnique Fédérale de Lausanne, CH–1015 Lausanne, Switzerland
J. E. Bidaux
Affiliation:
Institut de Génie Atomique, Ecole Polytechnique Fédérale de Lausanne, CH–1015 Lausanne, Switzerland
R. Schaller
Affiliation:
Institut de Génie Atomique, Ecole Polytechnique Fédérale de Lausanne, CH–1015 Lausanne, Switzerland
C. Esnouf
Affiliation:
Groupe d'Etudes de Métallurgie Physique et de Physique des Matériaux, Bât. 502, I.N.S.A. de Lyon, F–69621 Villeurbanne, France
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Abstract

Differential scanning calorimetry and transmission electron microscopy have been used to study thermal fatigue due to diffusionless phase transformation cycling in pure cobalt. Thermal cycling through the allotropic (hcp ↔ fcc) transformation results in a temperature shift of the calorimetric peaks, which means a delay of the transformation. In addition, the transformation enthalpy, which is greater on heating than on cooling, diminishes when the number of transformation cycles increases. This is interpreted as being due to an evolution of the microstructure. Transmission electron microscopy shows the appearance of transformation-induced defects, which are mainly sessile dislocations. We can interpret the calorimetry results (enthalpy evolution and transformation delay) as due to the interactions between interface dislocations and these sessile dislocations.

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Articles
Information
Journal of Materials Research , Volume 5 , Issue 4 , April 1990 , pp. 769 - 775
Copyright
Copyright © Materials Research Society 1990

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References

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