Modeling of structural and compositional homogenization of plutonium-1 weight percent gallium alloys

Mitchell, Jeanette; Gibbs, Frank E.; Zocco, T.G.; Pereyra, R. A.

doi:10.1007/s11661-001-1000-2

Cited by 28 publications

(15 citation statements)

References 4 publications

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“…This process generally requires ϳ100 hours for complete homogenization at temperatures of ϳ450°C. [5] The sample shown in Figure 5 was annealed for 50 hours at 420°C and the gray-scale variations within grains indicates that there is still significant compositional zonation of Ga.…”

Section: Microstructural Influences On Phase Stabilitymentioning

confidence: 99%

Phase stability and phase transformations in plutonium and plutonium-gallium alloys

Mitchell

Stan

Schwartz

et al. 2004

Metall Mater Trans A

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The complexity of phase stability and transformations in plutonium alloys is reflected in the plutoniumgallium (Pu-Ga) phase diagram, which is perhaps the most complex of all binary systems. Although many investigations have explored phase equilibria, transformation systematics, and structure/property relations in the Pu-Ga system, many outstanding problems remain and new issues regularly appear. In this article, we describe recent dilatometry and calorimetry measurements on pure plutonium and plutonium-gallium alloys. We also present recent phase diagram modeling that attempts to unravel differences between the U.S. and Russian Pu-Ga phase diagrams. The ultimate goal of this work is to produce the first internally consistent database of thermophysical properties of this system so that a true equilibrium phase diagram can be produced and so that stability can be predicted over a range of conditions.

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Section: Microstructural Influences On Phase Stabilitymentioning

confidence: 99%

Phase stability and phase transformations in plutonium and plutonium-gallium alloys

Mitchell

Stan

Schwartz

et al. 2004

Metall Mater Trans A

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“…A Pu-2.0 at.% Ga alloy was annealed at 460 °C for 534 hours to ensure a single-phase δ-Pu material with a homogeneous gallium distribution [6,7]. Subsequently, the sample, a 2.8 mm diameter cylinder with a mass of 177.92 mg, was cut from the annealed Pu-2.0 at.% Ga alloy.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2008

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The gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete lowtemperature 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.

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“…In performing sequential continuous cooling and heating experiments, Hecker et al [47] and Mitchell et al [51] have demonstrated that the amount of δ " α' transformation in Pu -1.8 and 2.0 at.% Ga alloys decreases with each thermal cycle even though it appears that all α′ reverts to δ during the heating portion of the cycle. In very recent work, Blobaum et al have shown that the amount of the δ " α' transformation is dependent on details of the thermal cycling [36].…”

Section: The δ → α′ Isothermal Martensitic Transformationmentioning

confidence: 99%

Opportunities in Plutonium Metallurgical Research*

Schwartz

2006

MRS Proc.

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This is an exciting time to be involved in plutonium metallurgical research. Over the past few years, there have been significant advances in our understanding of the fundamental materials science of this unusual metal, particularly in the areas of self-irradiation induced aging of Pu, the equilibrium phase diagram, the homogenization of δ-phase alloys, the crystallography and morphology of the α'-phase resulting from the isothermal martensitic phase transformation, and the phonon dispersion curves, among many others. In addition, tremendous progress has been made, both experimentally and theoretically, in our understanding of the condensed matter physics and chemistry of the actinides, particularly in the area of electronic structure. Although these communities have made substantial progress, many challenges still remain. This brief overview will address a number of important challenges that we face in fully comprehending the metallurgy of Pu with a specific focus on aging and phase transformations.

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Modeling of structural and compositional homogenization of plutonium-1 weight percent gallium alloys

Cited by 28 publications

References 4 publications

Phase stability and phase transformations in plutonium and plutonium-gallium alloys

Phase stability and phase transformations in plutonium and plutonium-gallium alloys

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

Opportunities in Plutonium Metallurgical Research*

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