Measurement of intrinsic diffusion coefficients of Al and Ni in Ni3Al using Ni/NiAl diffusion couples

The diffusion behavior of Al and Ni in Ni3Al with the Ll(2)-type crystal structure is examined by measuring intrinsic diffusion coefficients. First, interdiffusion coefficients are determined using Ni/NiAl diffusion couples forming a Ni3Al phase at the interface. The intrinsic diffusion coefficients are then determined from the interdiffusion coefficients and velocities of the Kirkendall interface with respect to the Matano plane through the Darken equation. It is shown that the intrinsic diffusion coefficients of Al and Ni in Ni3Al are of almost equal magnitude in the investigated temperature range (1423-1523 K). This conclusion is evaluated within the experimental error involved in the determination of the Matano plane. The self-diffusion coefficient of Al in Ni3Al is derived from the intrinsic diffusion coefficients of Al and Ni in Ni3Al and is compared with the estimation reported in the literature. It is shown that the present results support the diffusion mechanisms considering anti-site defects. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.