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

Journal Article · Sat Oct 01 04:00:00 EDT 2011 · Metallurgical and Materials Transactions A

DOI:https://doi.org/10.1007/s11661-011-0733-9· OSTI ID:1024911

Perez, E; Keiser, Jr, D D; Sohn, Y H

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 degrees 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-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43, and cubic-UMo2Al20 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 U6Mo4Al43 phase, which exhibits poor irradiation behavior that includes void formation and swelling.

• Research Organization: Idaho National Laboratory (INL)
• Sponsoring Organization: DOE - NA
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1024911
• Report Number(s): INL/JOU-11-21235
• Journal Information: Metallurgical and Materials Transactions A, Journal Name: Metallurgical and Materials Transactions A Journal Issue: 10 Vol. 42A; ISSN 1073-5623
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ALLOYS
DIFFUSION
ELECTRON DIFFRACTION
ELECTRON PROBES
IRRADIATION
MICROANALYSIS
MICROSTRUCTURE
MODIFICATIONS
RESEARCH AND TEST REACTORS
RESEARCH REACTORS
SCANNING ELECTRON MICROSCOPY
SUPERSATURATION
SWELLING
TRANSMISSION ELECTRON MICROSCOPY
diffusion
nuclear fuels
uranium molybdenum alloys