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Title: Investigation of Interdiffusion Behavior in the Mo-Zr Binary System via Diffusion Couple Studies

Zirconium has recently garnered attention for use as a diffusion barrier between U–Mo metallic nuclear fuels and Al alloy cladding. In order to gain a fundamental understanding of the diffusional interactions, the interdiffusion behavior in the binary Mo–Zr system was investigated via solid-to-solid diffusion couples annealed in the temperature range of 750 to 1050 degrees C. A combination of scanning electron microscopy, X-ray energy dispersive spectroscopy, and electron probe microanalysis were used to examine the microstructure and concentration profiles across the interdiffusion zone. A large __-Zr (cI2) solid solution layer and a thin (approximately 1–2 um) layer of Mo2Zr (cF24) developed in all couples. Parabolic growth constants and concentration dependent interdiffusion coefficients were calculated for the Mo2Zr and Zr solid solution phases, respectively. The pre-exponential factor and activation energy for growth of the Mo2Zr phase were determined to be approximately 6.5 × 10- 15 m2/s and 90 kJ/mol, respectively. The interdiffusion coefficient in ___-Zr solid solution decreased with an increase in Mo concentration. Both the pre-exponential factors (2 × 10- 8 m2/s at 2 at.% Mo to near 5 × 10- 8 m2/s at 9 at.% Mo) and activation energies (140 kJ/mol at 2 at.% Mo to approximately 155 kJ/molmore » at 9 at.% Mo) of interdiffusion coefficients were determined to increase with an increase in Mo concentration.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0263-4368
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Refractory Metals and Hard Materials; Journal Volume: 43
Research Org:
Idaho National Laboratory (INL)
Sponsoring Org:
Country of Publication:
United States
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; diffusion; diffusion couples; interdiffusion; interdiffusion coefficients; molybdenum; nuclear fuel; zirconium