Characterization of the interaction layer in diffusion couples U-7 wt.%Mo/Al 6061 alloy at 550 °C and 340 °C.

Mirandou, M.; Aricó, S.F.; Balart, S.; Gribaudo, L.M.

doi:10.1016/j.matchar.2009.02.010

Cited by 33 publications

(56 citation statements)

References 14 publications

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“…In FSW diffusion couples, Keiser et al 11 mentions that the Al and Si content vary significantly within the IL, but the sum of the two remains constant around 70 at.% based on EDS/transmission electron microscopy (TEM) results. Very similar results were found by Mirandou et al 20,35 These results are consistent with most of the diffusion couple studies.…”

Section: Mo and Si Contentsupporting

confidence: 92%

“…This has been observed in U(Mo)/Al 6061 by Keiser 11 and Mirandou et al 35 at 500C and 550C. Both works agree in that no PFZ is observed but Si is accumulated in the IL.…”

Section: The Precipitate-free Zone (Pfz)supporting

confidence: 64%

“…20,35 While the same phases were often found regardless of temperature, Si was more easily concentrated in the IL at 340C, especially if the matrix had a lesser amount of Si.…”

Section: Effect Of Temperaturementioning

confidence: 89%

“…Both works agree in that no PFZ is observed but Si is accumulated in the IL. At 340C Mirandou et al 35 reported Si content as high as 58 at.% within the IL and the presence of a PFZ. Similar behavior was observed in U(Mo)/Al A356 (7 wt% Si) by Mirandou et al 20 at 550C and 340C.…”

Section: The Precipitate-free Zone (Pfz)mentioning

confidence: 99%

“…Using couples formed by FSW and after a thermal treatment at 550°C, Mirandou et al 20,35 identified UAl 3 , U(Al,Si) 3 , and U 6 Mo 4 Al 43 phases in the IL using XRD. They conducted an investigation using high-intensity XRD with synchrotron radiation.…”

Section: Phase Identificationmentioning

confidence: 99%

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Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

Porter¹

2010

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SUMMARYPublished data concerning the interaction layer (IL) formed between U-xMo fuel alloy and aluminum (Al)-based matrix or cladding materials was reviewed, including the effects of silicon (Si) content in the matrix/cladding, molybdenum (Mo) content in the fuel, pre-irradiation thermal treatments, irradiation, and test temperature. The review revealed that tests conducted in the laboratory produce results different from those conducted in an irradiation environment. However, the laboratory testing relates well to thermal treatments performed prior to irradiation and helps in understanding the effects that these pre-irradiation treatments have on in-reactor performance. A small, Si-enriched IL, formed during a step in the fabrication process, seems to be stable during irradiation, helping to prevent the rapid growth of an irradiation-induced IL. Moreover, the Si-enriched IL seems to be important in delaying the onset of rapid growth of fission gas bubbles.Conclusions from irradiated fuels data have been repeated many times in the literature review. However, as related to the "Desired Characteristics of the IL" mentioned near the beginning of this report, several more conclusions can be drawn:1. An IL with phases akin to UAl 3 is desired for optimum fuel performance, but at low temperatures, and especially in an irradiation atmosphere, the desired (Al+Si)/(U+Mo) ratio of three is difficult to produce. When the fuel operating temperature is low, it is important to create a pre-irradiation IL enriched in Si. This pre-formed IL is relatively stable, performs well in terms of swelling resistance, and prevents rapid IL growth during irradiation. Fabrication-related heat treatments should be limited in order to maintain a thin, Si-enriched layer containing potentially beneficial phases.2. At higher operating temperatures (>150-170°C), IL formation in reactor may not be so dependent on pre-irradiation IL formation, especially at high burnup; a pre-fabricated IL seems to be less stable at high burnup and high operating temperature. Moreover, the (Al+SI)/(U+Mo) ratio of three occurs more often at higher temperature. For these two reasons, it is important at high operating temperature to also have a matrix with significant Si content to create an IL in-reactor with the right characteristics.3. Out-of-reactor testing seems to indicate that Si in the matrix material is required in some concentration (2%, 5%, ?) to provide for a thin, Si-enriched IL formed before irradiation of a fuel plate. It ensures that the IL contains beneficial phases or prevents formation of some known to promote poor fuel performance. Significant progress has been made in determining the desired characteristics of the IL.4. The use of a fuel with stable gamma phase appears to allow more predictable performance regarding both a beneficial pre-irradiation layer and the fuel performance (low swelling) to high burnup. Destabilization of the gamma phase may create problems with IL breakaway growth.5. A theory whereby prevention of the U 6 Mo 4 Al 43 comp...

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Section: Mo and Si Contentsupporting

confidence: 92%

“…This has been observed in U(Mo)/Al 6061 by Keiser 11 and Mirandou et al 35 at 500C and 550C. Both works agree in that no PFZ is observed but Si is accumulated in the IL.…”

Section: The Precipitate-free Zone (Pfz)supporting

confidence: 64%

“…20,35 While the same phases were often found regardless of temperature, Si was more easily concentrated in the IL at 340C, especially if the matrix had a lesser amount of Si.…”

Section: Effect Of Temperaturementioning

confidence: 89%

Section: The Precipitate-free Zone (Pfz)mentioning

confidence: 99%

Section: Phase Identificationmentioning

confidence: 99%

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Interaction Layer Characteristics in U-xMo Dispersion/Monolithic Fuels

Porter¹

2010

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Phase Constituents and Microstructure of Interaction Layer Formed in U-Mo Alloys vs Al Diffusion Couples Annealed at 873 K (600 °C)

Perez

Keiser

Sohn

2011

Metall Mater Trans A

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U-Mo dispersion and monolithic fuels are being developed to fulfill the requirements for research reactors, under the Reduced Enrichment for Research and Test Reactors program. In dispersion fuels, particles of U-Mo alloys are embedded in the Al-alloy matrix, while in monolithic fuels, U-Mo monoliths are roll bonded to the Al-alloy matrix. In this study, interdiffusion and microstructural development in the solid-to-solid diffusion couples, namely, U-15.7 at. pct Mo (7 wt pct Mo) vs pure Al, U-21.6 at. pct Mo (10 wt pct Mo) vs pure Al, and U-25.3 at. pct Mo (12 wt pct Mo) vs pure Al, annealed at 873 K (600°C) for 24 hours, were examined in detail. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA) were employed to examine the development of a very fine multiphase interaction layer with an approximately constant average composition of 80 at. pct Al. Extensive TEM was carried out to identify the constituent phases across the interaction layer based on selected area electron diffraction and convergent beam electron diffraction (CBED). The cubic-UAl 3 , orthorhombic-UAl 4 , hexagonal-U 6 Mo 4 Al 43 , and cubicUMo 2 Al 20 phases were identified within the interaction layer that included two-and three-phase layers. Residual stress from large differences in molar volume, evidenced by vertical cracks within the interaction layer, high Al mobility, Mo supersaturation, and partitioning toward equilibrium in the interdiffusion zone were employed to describe the complex microstructure and phase constituents observed. A mechanism by compositional modification of the Al alloy is explored to mitigate the development of the U 6 Mo 4 Al 43 phase, which exhibits poor irradiation behavior that includes void formation and swelling.

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