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Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. % Ga

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:
jeffries4@llnl.gov, Lawrence Livermore National Laboratory, Materials Science and Technology Division, 7000 East Avenue, L-350, Livermore, CA, 94550, United States
Kerri J. M. Blobaum
Affiliation:
blobaum1@llnl.gov, Lawrence Livermore National Laboratory, Chemistry, Materials, Earth, and Life Sciences Directorate, Livermore, CA, 94550, United States
Mark A. Wall
Affiliation:
wall1@llnl.gov, Lawrence Livermore National Laboratory, Chemistry, Materials, Earth, and Life Sciences Directorate, Livermore, CA, 94550, United States
Adam J. Schwartz
Affiliation:
schwartz6@llnl.gov, Lawrence Livermore National Laboratory, Physical Sciences Directorate, Livermore, CA, 94550, United States
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Abstract

The gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable δ phase to the gallium-containing, monoclinic α′ phase near -100 °C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation (TTT) diagram, where two nose temperatures anchoring an upper- and lower-C describe minima in the time for the initiation of transformation. The underlying mechanisms responsible for the double-C behavior are currently unresolved, although recent experiments suggest that a conditioning treatment—wherein, following an anneal at 375 °C, the sample is held at a sub-anneal temperature for a period of time—significantly influences the upper-C of the TTT diagram. As such, elucidating the effects of the conditioning treatment upon the δ⟶α′ transformation can provide valuable insights into the fundamental mechanisms governing the double-C kinetics of the transition. Following a high-temperature anneal, a differential scanning calorimeter (DSC) was used to establish an optimal conditioning curve that depicts the amount of α′ formed during the transformation as a function of conditioning temperature for a specified time. With the optimal conditioning curve as a baseline, the DSC was used to explore the circumstances under which the effects of the conditioning treatment were destroyed, resulting in little or no transformation.

Keywords

Puphase transformationcalorimetry
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1104: Symposium NN – Actinides 2008—Basic Science, Applications and Technology , 2008 , 1104-NN01-06
Copyright
Copyright © Materials Research Society 2008

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