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Low-Temperature Aging and Phase Stabiliy of U6Nb

Published online by Cambridge University Press:  01 February 2011

L. M. Hsiung ,
C. L. Briant  and
K. R. Chasse
L. M. Hsiung
Affiliation:
Lawrence Livermore National Laboratory, Chemistry and Materials Science Directorate, P.O. Box 808, L-352, Livermore, CA 94551–9900.
C. L. Briant
Affiliation:
Brown University, Division of Engineering, Providence, RI 02912.
K. R. Chasse
Affiliation:
Brown University, Division of Engineering, Providence, RI 02912.
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Abstract

Aging behavior and phase stability of a water-quenched U-6wt%Nb (U-14at%Nb) alloy artificially aged at 200°C and naturally aged at ambient temperature for 15 years have been investigated using Vickers hardness test, X-ray diffraction analysis, and transmission electron microscopy techniques. Age hardening/softening phenomenon is observed from the artificially aged samples according to microhardness measurement. The age hardening can be rationalized by the occurrence of spinodal decomposition, or fine scale of Nb segregation, which results in the formation of a nano-scale modulated structure within the artificially aged samples. Coarsening of the modulated structure after prolonged aging leads to the age softening. The occurrence of chemical ordering (disorder-order transformation) is found in the naturally aged sample based upon the observations of antiphase domain boundaries (APB's) and superlattice diffraction patterns. A possible superlattice structure is accordingly proposed for the chemically ordered phase observed in the naturally aged alloy sample.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 802: Symposium DD – Actinides - Basic Science, Applications, and Technology , 2003 , DD1.6
Copyright
Copyright © Materials Research Society 2004

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References

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