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

Alexander A Kodentsov,Frans J J Van Loo

doi:10.1007/s00706-012-0750-4

Alexander A Kodentsov, Frans J J Van Loo

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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.%.Graphical abstract

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The practical interest in the Nb–Ni–Cr system is generated mainly by the fact that Ni–Cr-based alloys are important corrosion-resistant high-temperature materials
Under these circumstances the low-temperature modification of the NbCr2 Laves phase can dissolve up to 6 at.% of nickel, but further increase of the Ni content stabilizes the hexagonal 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 isothermal cross section through the ternary diagram was constructed by the traditional method of equilibrated alloys and diffusion couple technique

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The practical interest in the Nb–Ni–Cr system is generated mainly by the fact that Ni–Cr-based alloys are important corrosion-resistant high-temperature materials. 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.

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