Ternary Diffusion in a RuAl-NiAl Couple |
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Authors: | KN Kulkarni B Tryon TM Pollock MA Dayananda |
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Affiliation: | (1) School of Materials Engineering, Purdue University, West Lafayette, IN, USA;(2) Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA |
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Abstract: | A ternary diffusion couple assembled with NiAl and RuAl disks and annealed at 1100 °C was examined by scanning electron microscopy
and analyzed for concentration profiles by electron microprobe analysis. Complete mutual solid solubility with continuous
variations in compositions was observed between the binary B2 aluminides. Ternary interdiffusion coefficients were determined with the aid of a program called MultiDiFlux over two composition ranges, one Ru-rich and the other Ni-rich, within the diffusion zone. The interdiffusion coefficient,
varies little with variation in composition, but the interdiffusion coefficient, decreases by an order of magnitude from the Ni-rich region to the Ru-rich region. is larger than in the Ni-rich region by an order of magnitude. The cross coefficients, and , are both positive. is comparable in magnitude to the main coefficient in the Ni-rich region; hence, Ni interdiffusion flux is enhanced down a Ru concentration gradient but decreased against it.
Similarly, Ni interdiffusion is reduced down Al gradients. Characteristic depth parameters calculated for Ni and Ru are larger
on the NiAl side than on the RuAl side. Approximate calculations of cumulative intrinsic diffusion fluxes past a Kirkendall
plane suggest that the atomic mobility of Ni is larger than that of Ru. |
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Keywords: | modeling nickel aluminide ruthenium aluminide ternary diffusion |
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