Fe-Nb-Zn (Iron-Niobium-Zinc)

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Section II: Phase Diagram Evaluations

Fe-Nb-Zn (Iron-Niobium-Zinc) V. Raghavan

Recently, [2009Tu] determined an isothermal section for this ternary system at 450 °C.

Binary Systems The Fe-Nb phase diagram has the following intermediate phases: Fe2Nb (C14, MgZn2-type hexagonal) and Fe7Nb6 (D85, Fe7W6-type rhombohedral; denoted l). In the Fe-Zn system, the intermediate phases are: C (Fe3 Zn10 ; Cu5 Zn8 type cubic), C1 ðFe11 Zn40 ; cubic), d (FeZn10 -type hexagonal) and f (CoZn13 -type monoclinic). The following intermediate phases form by peritectic reactions in the Nb-Zn system [1992Mos]: NbZn, NbZn1:5 (hexagonal), NbZn2 ðC36; MgNi2 -type hexagonal), NbZn3 ðL12 ; AuCu3 type cubic), NbZn7 , and NbZn15 . The stability of a reported phase at Nb3 Zn is not known [1992Mos].

Ternary Isothermal Section With starting metals of 99.99% purity, [2009Tu] prepared 8 equilibrated alloys and Fe-Nb/Zn diffusion

couples. The time of equilibration was 60 days at 450  C and the diffusion anneal was 30 days at the same temperature, followed water quenching. The phase equilibria were studied with scanning electron microscope equipped with wavelength-dispersive and energy-dispersive x-ray spectroscopy and x-ray powder diffraction. The measured compositions of the co-existing phases were listed. The isothermal section at 450  C constructed by [2009Tu] is shown in Fig. 1. The ternary phase T, which is isostructural with the binary C1, has a homogeneity range. The binary Fe-Zn compounds d; C1 and C dissolve 0.1, 0.4 and 1.0 mass% Nb respectively. Fe2 Nb dissolves up to 6.2 at.% Zn.

References 1992Mos: Z. Moser, The Nb-Zn (Niobium-Zinc) System, J. Phase Equilib., 1992, 13(4), p 425-429 2009Tu: H. Tu, X. Su, F. Yin, X. Wang, and J. Wang, 450  C Isothermal Section of the Zn-Fe-Nb Ternary System at the Zn-Rich Corner, J. Alloys Compd., 2009, 485, p 270-274

Fig. 1 Fe-Nb-Zn isothermal section at 450  C [2009Tu]

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Journal of Phase Equilibria and Diffusion Vol. 32 No. 2 2011

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