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

Conference ·
; ; ;
The gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable {delta} phase to the gallium-containing, monoclinic {alpha}{prime} 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 {delta} {yields} {alpha}{prime} 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 {alpha}{prime} 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.
Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA
Sponsoring Organization:
USDOE
DOE Contract Number:
W-7405-ENG-48
OSTI ID:
945126
Report Number(s):
LLNL-PROC-402757
Country of Publication:
United States
Language:
English

References (6)

Nucleation and growth of the α′ martensitic phase in Pu–Ga alloys journal September 2006
Supporting evidence for double-C curve kinetics in the isothermal δ→α′ phase transformation in a Pu–Ga alloy journal October 2007
Phase transformation in Pu–Ga alloys at low temperature and under pressure: limit stability of the δ phase journal June 1998
Orientation Relationship, Habit Plane, Twin Relationship, Interfacial Structure, and Plastic Deformation Resulting from the δ → α′ Isothermal Martensitic Transformation in Pu-Ga Alloys journal February 2007
Modeling of structural and compositional homogenization of plutonium-1 weight percent gallium alloys journal March 2001
Evidence of transformation bursts during thermal cycling of a Pu-Ga alloy journal March 2006

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Related Subjects

36 MATERIALS SCIENCE
ALLOYS
AMBIENT TEMPERATURE
CALORIMETERS
FASTENING
KINETICS
PROBES
TRANSFORMATIONS