Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7963341 | Journal of Nuclear Materials | 2018 | 33 Pages |
Abstract
The microstructural development and diffusion kinetics were examined for the binary U vs. Zr system using solid-to-solid diffusion couples, U vs. Zr, annealed at 580â¯Â°C for 960â¯h, 650â¯Â°C for 480â¯h, 680â¯Â°C for 240â¯h, and 710â¯Â°C for 96â¯h. Scanning and transmission electron microscopies with X-ray energy dispersive spectroscopy were employed for detailed microstructural and compositional analyses. Interdiffusion and reaction in U vs. Zr diffusion couples primarily produced: δ-UZr2 solid solution (hP3) and αâ²-U at 580â¯Â°C; and (γU,βZr) solid solution (cI2) and αâ²-U at 650°, 680° and 710â¯Â°C. The αâ²-phase was confirmed as a reduced variant of the α-U orthorhombic structure with lattice parameters, aâ¯Ãâ¯bâ¯Ãâ¯câ¯=â¯2.65â¯Ãâ¯5.40â¯Ãâ¯4.75 (Ã
) with a negligible solubility for Zr at room temperature. Concentration profiles were examined to determine interdiffusion coefficients, integrated interdiffusion coefficients, and intrinsic diffusion coefficients using Boltzmann-Matano, Wagner, and Heumann analyses, respectively. Composition-dependence of interdiffusion coefficients were documented for α-U, δ-UZr2 (at 580â¯Â°C) and (γU,βZr) solid solution (at 650°, 680° and 710â¯Â°C). U was determined to intrinsically diffuse faster than Zr, approximately by an order of magnitude, in the δ-UZr2 at 580â¯Â°C, and (γU,βZr) phases at 650°, 680° and 710â¯Â°C. Based on Darken's approach, thermodynamic data available in literature were coupled to estimate the tracer diffusion coefficients and atomic mobilities of U and Zr.
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Authors
Y. Park, R. Newell, A. Mehta, D.D. Jr., Y.H. Sohn,