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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 annealed (1,100 °C, 196 h) diffusion couples based on two-phase alloy with the nominal composition Ni50Cr50 and a the two-phase alloy Ni60Nb40 and b pure Nb. Note that domains of the Cr-based solid solution (Crss) present within the microstructure of the Ni50Cr50 alloy exhibit a dark contrast (the various phases on the micrographs are denoted by their binary formulae, and T is the pseudo-ternary phase)
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Fig2: BEIs of the reaction zones developed in the annealed (1,100 °C, 196 h) diffusion couples based on two-phase alloy with the nominal composition Ni50Cr50 and a the two-phase alloy Ni60Nb40 and b pure Nb. Note that domains of the Cr-based solid solution (Crss) present within the microstructure of the Ni50Cr50 alloy exhibit a dark contrast (the various phases on the micrographs are denoted by their binary formulae, and T is the pseudo-ternary phase)

Mentions: When another two-phase material with the nominal composition Ni50Cr50, which after equilibration at 1,100 °C and quenching in water is a mixture of face-centred cubic (FCC) Ni-based and body-centred cubic (BCC) Cr-based solid solutions [8], was used as the end-member of the diffusion couple, the interfacial reaction with the Ni60Nb40 alloy also resulted in the formation of a continuous layer of the pseudo-ternary intermetallic (Fig. 2a). An interesting feature here is that the product layer of the T phase is not in direct contact with the initial two-phase substrate, but separated from it by the layer of Cr-based solid solution. This implies that in the Nb–Ni–Cr system the pseudo-ternary compound T is not in equilibrium with the Ni-based solid solution at 1,100 °C.Fig. 2


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 annealed (1,100 °C, 196 h) diffusion couples based on two-phase alloy with the nominal composition Ni50Cr50 and a the two-phase alloy Ni60Nb40 and b pure Nb. Note that domains of the Cr-based solid solution (Crss) present within the microstructure of the Ni50Cr50 alloy exhibit a dark contrast (the various phases on the micrographs are denoted by their binary formulae, and T is the pseudo-ternary phase)
© Copyright Policy
Related In: Results  -  Collection

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

Fig2: BEIs of the reaction zones developed in the annealed (1,100 °C, 196 h) diffusion couples based on two-phase alloy with the nominal composition Ni50Cr50 and a the two-phase alloy Ni60Nb40 and b pure Nb. Note that domains of the Cr-based solid solution (Crss) present within the microstructure of the Ni50Cr50 alloy exhibit a dark contrast (the various phases on the micrographs are denoted by their binary formulae, and T is the pseudo-ternary phase)
Mentions: When another two-phase material with the nominal composition Ni50Cr50, which after equilibration at 1,100 °C and quenching in water is a mixture of face-centred cubic (FCC) Ni-based and body-centred cubic (BCC) Cr-based solid solutions [8], was used as the end-member of the diffusion couple, the interfacial reaction with the Ni60Nb40 alloy also resulted in the formation of a continuous layer of the pseudo-ternary intermetallic (Fig. 2a). An interesting feature here is that the product layer of the T phase is not in direct contact with the initial two-phase substrate, but separated from it by the layer of Cr-based solid solution. This implies that in the Nb–Ni–Cr system the pseudo-ternary compound T is not in equilibrium with the Ni-based solid solution at 1,100 °C.Fig. 2

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