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Evidence of Embryo Formation as a Precursor to the Delta to Alpha-Prime Transformation in a Pu-Ga Alloy

Published online by Cambridge University Press:  26 February 2011

Kerri J.M. Blobaum ,
C. R. Krenn ,
M. A. Wall ,
T. B. Massalski  and
A. J. Schwartz
Kerri J.M. Blobaum
Affiliation:
blobaum1@llnl.gov, Lawrence Livermore National Laboratory, Chemistry and Materials Science, L-356, 7000 East Avenue, Livermore, CA, 94550, United States, (925) 422-3289, (925) 424-4737
C. R. Krenn
Affiliation:
krenn1@llnl.gov, Lawrence Livermore National Laboratory, United States
M. A. Wall
Affiliation:
wall1@llnl.gov, Lawrence Livermore National Laboratory, Chemistry and Materials Science Directorate, United States
T. B. Massalski
Affiliation:
massalsk@andrew.cmu.edu, Carnegie Mellon University, Department of Material Science and Engineering, United States
A. J. Schwartz
Affiliation:
schwartz6@llnl.gov, Lawrence Livermore National Laboratory, Physics and Advanced Technologies Directorate, United States
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Abstract

It was experimentally observed that a single Pu-2.0 at% Ga sample can be thermally cycled many times, with nearly the same amount of transformation and reversion during each cycle, provided that the sample is annealed at 375°C for 8 hours and then conditioned at 25°C for at least 6 hours. The ambient temperature conditioning period is crucial for obtaining the same amount of transformation to alpha-prime in each thermal cycle. Here, we present results from a series of experiments that investigate the effects of conditioning time and temperature on alpha-prime_formation. When the sample is conditioned at 25°C for times between 0 and 6 hours, the amount of alpha-prime formed is a function of conditioning time. For conditioning treatments between 6 and 70 hours, however, the amount of alpha-prime_formed is nearly constant. Conditioning treatments at –50°C, 150°C, and 370°C all resulted in less alpha-prime_formation than the 25°C treatments. We hypothesize that embryos of the thermodynamically stable alpha phase form during the conditioning treatments, and these embryos form alpha-prime upon subsequent cooling. This result is an indirect confirmation of the Russian Pu-Ga equilibrium phase diagram.

Keywords

phase transformationactinidecalorimetry
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 893: Symposium JJ – Actinides 2005 – Basic Science, Applications and Technology , 2005 , 0893-JJ04-06
Copyright
Copyright © Materials Research Society 2006

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References

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