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Phase relations in the Nb-Ni-Cr system at 1,100 °C.

Kodentsov AA, van Loo FJ - Monatsh. Chem. (2012)

Bottom Line: It was found that nearly 28 at.% of Cr can be dissolved in the μ phase (Nb7Ni6) at this temperature, and the solubility of chromium in NbNi3 is approximately 5 at.%.The presence of this pseudo-ternary compound which is in equilibrium with all binary intermetallics and body-centred cubic (BCC) Nb- and Cr-based solid solutions largely determines the topology of the isotherm at 1,100 °C.The formation of this phase was also observed in the reaction zone between Nb and Ni-Cr solid solution when chromium concentration exceeded 15 at.%.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Materials and Interface Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.

ABSTRACT

Abstract: The isothermal cross section through the ternary phase diagram Nb-Ni-Cr at 1,100 °C was constructed by means of diffusion couples and equilibrated alloys. It was found that nearly 28 at.% of Cr can be dissolved in the μ phase (Nb7Ni6) at this temperature, and the solubility of chromium in NbNi3 is approximately 5 at.%. Under these circumstances the low-temperature (cubic) modification of the NbCr2 Laves phase can dissolve up to 6 at.% of nickel, but further increase of the Ni content (up to approximately 10 at.%) stabilizes the hexagonal (high-temperature) modification of the Laves phase. The presence of this pseudo-ternary compound which is in equilibrium with all binary intermetallics and body-centred cubic (BCC) Nb- and Cr-based solid solutions largely determines the topology of the isotherm at 1,100 °C. The formation of this phase was also observed in the reaction zone between Nb and Ni-Cr solid solution when chromium concentration exceeded 15 at.%.

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BEIs of the reaction zones developed in the diffusion couples based on Nb and Ni–Cr solid solution alloys with different Cr content a 5 at.%, b 15 at.%, and c 25 at.%
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Fig5: BEIs of the reaction zones developed in the diffusion couples based on Nb and Ni–Cr solid solution alloys with different Cr content a 5 at.%, b 15 at.%, and c 25 at.%

Mentions: The microstructure of the reaction zones in the diffusion couples based on niobium and various Ni–Cr solid solution alloys are shown in Fig. 5. Solid-state reaction of Ni–5 at.% Cr solid solution with Nb at 1,100 °C results in reaction products somewhat similar to those that would be expected (from the phase diagram) in a binary Nb/Ni couple [8]. Two binary intermetallic compounds, viz. NbNi3 and μ-Nb7Ni6 with very low chromium content (<0.3 at.%), are formed in the transition zone (Fig. 5a). It was found that the reaction layer growth follows a parabolic kinetics profile which is indicative of a diffusion-controlled process.Fig. 5


Phase relations in the Nb-Ni-Cr system at 1,100 °C.

Kodentsov AA, van Loo FJ - Monatsh. Chem. (2012)

BEIs of the reaction zones developed in the diffusion couples based on Nb and Ni–Cr solid solution alloys with different Cr content a 5 at.%, b 15 at.%, and c 25 at.%
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4494769&req=5

Fig5: BEIs of the reaction zones developed in the diffusion couples based on Nb and Ni–Cr solid solution alloys with different Cr content a 5 at.%, b 15 at.%, and c 25 at.%
Mentions: The microstructure of the reaction zones in the diffusion couples based on niobium and various Ni–Cr solid solution alloys are shown in Fig. 5. Solid-state reaction of Ni–5 at.% Cr solid solution with Nb at 1,100 °C results in reaction products somewhat similar to those that would be expected (from the phase diagram) in a binary Nb/Ni couple [8]. Two binary intermetallic compounds, viz. NbNi3 and μ-Nb7Ni6 with very low chromium content (<0.3 at.%), are formed in the transition zone (Fig. 5a). It was found that the reaction layer growth follows a parabolic kinetics profile which is indicative of a diffusion-controlled process.Fig. 5

Bottom Line: It was found that nearly 28 at.% of Cr can be dissolved in the μ phase (Nb7Ni6) at this temperature, and the solubility of chromium in NbNi3 is approximately 5 at.%.The presence of this pseudo-ternary compound which is in equilibrium with all binary intermetallics and body-centred cubic (BCC) Nb- and Cr-based solid solutions largely determines the topology of the isotherm at 1,100 °C.The formation of this phase was also observed in the reaction zone between Nb and Ni-Cr solid solution when chromium concentration exceeded 15 at.%.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Materials and Interface Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.

ABSTRACT

Abstract: The isothermal cross section through the ternary phase diagram Nb-Ni-Cr at 1,100 °C was constructed by means of diffusion couples and equilibrated alloys. It was found that nearly 28 at.% of Cr can be dissolved in the μ phase (Nb7Ni6) at this temperature, and the solubility of chromium in NbNi3 is approximately 5 at.%. Under these circumstances the low-temperature (cubic) modification of the NbCr2 Laves phase can dissolve up to 6 at.% of nickel, but further increase of the Ni content (up to approximately 10 at.%) stabilizes the hexagonal (high-temperature) modification of the Laves phase. The presence of this pseudo-ternary compound which is in equilibrium with all binary intermetallics and body-centred cubic (BCC) Nb- and Cr-based solid solutions largely determines the topology of the isotherm at 1,100 °C. The formation of this phase was also observed in the reaction zone between Nb and Ni-Cr solid solution when chromium concentration exceeded 15 at.%.

No MeSH data available.


Related in: MedlinePlus