Study on diffusion and Kirkendall effect in diffusion triples for fcc Ni–Al–Ta alloys

Abstract

In the present work based on two diffusion triples, the composition-dependent interdiffusivity matrices in the fcc Ni–Al–Ta alloys at 1373K and 1473K were efficiently deduced by using our newly developed two-dimensional (2D) inverse scheme. This scheme determines interdiffusivities from point and one-dimensional (1D) diffusion path to 2D composition region, yet requires much less experimental efforts, with the measured 2D composition profiles being well reproduced. Further, the interdiffusivities deduced from the inverse scheme were directly compared with those extracted by the traditional Sauer-Freise method and Whittle-Green method based on nine diffusion couples designed for verification. The interdiffusivities inferred from two distinct ways are fairly consistent, either at the binary boundaries or at the intersection points within the ternary composition range. Besides, the interdiffusion flux and the shift of the Kirkendall plane over the whole diffusion zone were simulated by applying the present 2D inverse scheme. The resulting 2D mapping presents a non-uniform but curved Kirkendall plane, which is in contrast to the flat shape generated in 1D diffusion couples and well explained by the calculated diffusion variables.