Ternary Diffusion in a RuAl-NiAl Couple
Journal of Phase Equilibria and Diffusion(2007)
摘要
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 B 2 aluminides. Ternary interdiffusion coefficients were determined with the aid of a program called Multi DiFlux over two composition ranges, one Ru-rich and the other Ni-rich, within the diffusion zone. The interdiffusion coefficient, ∼D^Al_RuRu varies little with variation in composition, but the interdiffusion coefficient, ∼D^Al_NiNi decreases by an order of magnitude from the Ni-rich region to the Ru-rich region. ∼D^Al_NiNi is larger than ∼D^Al_RuRu in the Ni-rich region by an order of magnitude. The cross coefficients, ∼D^Al_NiRu and ∼D^Al_RuNi , are both positive. ∼D^Al_NiRu is comparable in magnitude to the main coefficient ∼D^Al_NiNi 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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关键词
nickel aluminide,ternary diffusion,modeling,ruthenium aluminide
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