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Enabling the Double-C Curve in Pu-Ga Alloy Time-Temperature-Transformation Diagrams

Published online by Cambridge University Press:  01 February 2011

Jason R. Jeffries ,
Kerri J. M. Blobaum ,
Mark A. Wall  and
Adam J. Schwartz
Jason R. Jeffries
Affiliation:
[email protected], Lawrence Livermore National Laboratory, Chemistry, Materials, Earth, and Life Sciences Directorate, 7000 East Avenue, L-350, Livermore, CA, 94550, United States
Kerri J. M. Blobaum
Affiliation:
[email protected], Lawrence Livermore National Laboratory, Livermore, CA, 94550, United States
Mark A. Wall
Affiliation:
[email protected], Lawrence Livermore National Laboratory, Livermore, CA, 94550, United States
Adam J. Schwartz
Affiliation:
[email protected], Lawrence Livermore National Laboratory, Livermore, CA, 94550, United States
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Abstract

Under ambient conditions, a Pu-2.0 at.% Ga alloy is retained in the metastable δ phase. Upon cooling to approximately -120 °C, the face-centered-cubic δ phase partially transforms to the metastable monoclinic α′ phase via a martensitic transformation. The kinetics of the δ⟶α′ transformation are reported to have double-C curve kinetics in a time-temperature-transformation (TTT) diagram, but the mechanisms responsible for this unusual behavior are not understood. Our work focuses on determining the underlying cause of the two noses. Optical microscopy has been used to investigate the role of “conditioning”—an isothermal hold at sub-anneal temperatures—on the δ⟶α′ transformation and to illuminate any disparities in transformation products. Conditioning was found to affect substantially the amount of transformation that occurs at particular points corresponding to both the upper- and lower-C of the TTT diagram.

Keywords

Puphase transformationmicrostructure
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1104: Symposium NN – Actinides 2008—Basic Science, Applications and Technology , 2008 , 1104-NN01-07
Copyright
Copyright © Materials Research Society 2008

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