Phase Constituents and Microstructure of Interaction Layer Formed in U-Mo Alloys vs Al Diffusion Couples Annealed at 873
- PDF / 1,229,530 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 65 Downloads / 156 Views
INTERACTIONS between c-phase (bcc) U-7 to 12 wt pct Mo and Al (fcc) alloys have been of recent interest, because U-Mo alloys can achieve the desired high U-density[1] and allow for reduced enrichment (e.g., Reduced Enrichment for Research and Test Reactors).[1,2] Two different designs of U-Mo fuels have been under consideration: U-Mo particles dispersed in Al matrix alloys and U-Mo monolith encased in Al clad alloys. In both cases, understanding of interactions between the U-Mo and Al alloys have proven critical, since the product of interactions can be quite complex with unfavorable physical and mechanical properties, including lower U-density, thermal conductivity, and toughness. The Mo stabilizes the c-U phase in the alloy, delaying the decomposition of the c-U (A2) to a-U (A20) and E. PEREZ, Graduate Research Assistant, and Y.H. SOHN, Professor, are with the Advanced Materials Processing and Characterization Center, Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816. Contact e-mail: [email protected] D.D. KEISER, Jr., Materials Scientist, is with the Nuclear Fuels and Materials Development Department, Idaho National Laboratory, Idaho Falls, ID 83415. Manuscript submitted June 1, 2010. Article published online May 25, 2011 METALLURGICAL AND MATERIALS TRANSACTIONS A
d-U2Mo (C11b) at low temperature, while maintaining the density of uranium necessary for proper reactor operation. Early studies in the U-Mo system by Dwight,[3] Ivanov et al.,[4,5] Streets and Stobe,[6] and Gomozov et al.[7] reported the cfi(a+d) decomposition with limited Mo solubility of approximately 0.12 at. pct at 873 K (600 C) in the a phase. Repas et al.[8] and Goldstein and Bar-Or[9] developed time-temperaturetransformation (TTT) diagrams for U-8 to 14 wt pct Mo alloys to summarize the c-phase stability as a function of Mo concentration. A relevant TTT diagram for U-10 wt pct Mo alloy is presented in Figure 1.[8] Parida et al.[10] reported the thermodynamic functions to describe the stability of the c phase, and several studies were carried out to examine the influence of Mo concentration and cooling rate on the cfi(a+d) decomposition and stability of the c phase,[11–13] including those as dispersion particles.[14–17] Under irradiation, however, the c-U phase is stabilized.[18–21] The interaction between the U-Mo dispersions in the Al-alloy matrix was examined by out-of-pile diffusion anneal experiments by Lee et al.,[11] who reported the development of UAl2 and UAl3 phases, and the cfi(a+d) decomposition, and by Ryu et al.,[12,13] who observed the UAl3, (U,Mo)Al3, and (U,Mo)Al4 phases. Keiser[22] examined the interaction with frictionstir-welded diffusion couples and reported the formation VOLUME 42A, OCTOBER 2011—3071
Fig. 2—Schematic ternary isothermal phase diagram for Al-rich region of the U-Mo-Al system for temperature range of interest.
Fig. 1—TTT diagram for U-10 wt pct Mo alloy adopted from Repas et al.[8]
of (U,Mo)(Al,Si)4 and (U,Mo)(Al,Si)2 phases. Perez et al.[23] anneale
Data Loading...
