Phase Stability and Transformations in the Zr2nixCu1-x Amorphous System
Journal Article
·
· Metallurgical and Materials Transactions A
OSTI ID:941075
Since Ni and Cu differ by only one valence electron, yet have nearly identical atomic sizes (1.27 vs 1.28 {angstrom} for Cu and Ni, respectively), the amorphous Zr{sub 2}N{sub x} Cu{sub 1-x} system is ideal for isolating the effects of electronic structure on short- and medium-range order and the concomitant influence of both the structure and order on devitrification pathways. Thermal analysis, time-resolved high-energy X-ray diffraction (HEXRD), and transmission electron microscopy (TEM) were used to follow metastable and stable crystalline phase formation during devitrification. Using HEXRD, we observed that the first devitrification product in the Zr{sub 2}Ni system is the C16 structure, if oxygen is kept sufficiently low, while the Zr{sub 2}Cu system forms the C11b structure. For x = 0.25, the initial devitrification involves forming coexisting C11b and C16 phases. When Ni is increased to x {ge} 0.50, the initial devitrification only involves the C16 structure. These results are in complete accord with electronic structure calculations showing that the enthalpy of formation for the C11b phase is favored for x = 0, while enthalpies for C11b and C16 are nearly identical for x = 0.25; the C16 phase has the most negative enthalpy for all compositions in which x > 0.25.
- Research Organization:
- Ames Laboratory (AMES), Ames, IA
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC02-07CH11358
- OSTI ID:
- 941075
- Report Number(s):
- IS-J 7322
- Journal Information:
- Metallurgical and Materials Transactions A, Journal Name: Metallurgical and Materials Transactions A Journal Issue: 8 Vol. 39A
- Country of Publication:
- United States
- Language:
- English
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