Delta/Alpha-Prime Phase Transformations in a Pu-Ga Alloy [electronic resource].

Published:: Washington, D.C. : United States. Dept. of Energy, 2005.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description:: PDF-FILE: 7 ; SIZE: 1.1 MBYTES pages
Additional Creators:: Lawrence Livermore National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information

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Summary:

In pure plutonium, the monoclinic α phase is the equilibrium phase at ambient temperature and pressure. The addition of a few percent of gallium, however, allows the fcc δ phase to be retained metastablely at ambient conditions. When the metastable δ phase is cooled to subambient temperatures, it partially transforms to the monoclinic α' phase, which has gallium supersaturated in the lattice. The α' phase reverts to the δ phase when the sample is heated above the ambient temperature. The martensite burst (M{sub b}) and reversion start (R{sub s}) temperatures are functions of the composition, heating rate, and prior thermal history. For a Pu-2.0 at% Ga alloy, the transformation hysteresis is approximately 150 C, which is large compared with other solid-solid phase transformations. Both the forward and reverse transformations are martensitic and proceed via a burst mode. Here, we use differential scanning calorimetry (DSC) and resistometry to perform fundamental studies of the α'/δ transformations with the goal of understanding how aging may affect δ phase stability, particularly the M{sub b} temperature. Because materials properties of the α' and δ phases are considerably different (including a density increase of 25% and an accompanying resistivity increase of 46% upon transformation from δ to α'), unexpected transformation to the α' phase is of particular interest to the stockpile stewardship community.

Report Numbers:

E 1.99:ucrl-conf-210321
ucrl-conf-210321

Subject(s):

Materials Science

Other Subject(s):

Note:

Published through SciTech Connect.
03/07/2005.
"ucrl-conf-210321"
Presented at: 26th Compatibility, Aging, and Stockpile Stewardship Conference, Aiken, SC (US), 04/26/2005--04/28/2005.
Schwartz, A J; Wall, M A; Blobaum, K M; Krenn, C R.

Funding Information:

W-7405-ENG-48

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