Development of different methods and their efficiencies for the estimation of diffusion coefficients following the diffusion couple technique

Abstract

The interdiffusion coefficients are estimated either following the Wagner's method expressed with respect to the composition (mol or atomic fraction) normalized variable after considering the molar volume variation or the den Broeder's method expressed with respect to the concentration (composition divided by the molar volume) normalized variable. On the other hand, the relations for estimation of the intrinsic diffusion coefficients of components as established by van Loo and integrated diffusion coefficients in a phase with narrow homogeneity range as established by Wagner are currently available with respect to the composition normalized variable only. In this study, we have first derived the relation proposed by den Broeder following the line of treatment proposed by Wagner. Further, the relations for estimation of the intrinsic diffusion coefficients of the components and integrated interdiffusion coefficient are established with respect to the concentration normalized variable, which were not available earlier. The veracity of these methods is examined based on the estimation of data in Ni-Pd, Ni-Al and Cu-Sn systems. Our analysis indicates that both the approaches are logically correct and there is small difference in the estimated data in these systems although a higher difference could be found in other systems. The integrated interdiffusion coefficients with respect to the concentration (or concentration normalized variable) can only be estimated considering the ideal molar volume variation. This might be drawback in certain practical systems.

Composition dependence of tracer diffusion coefficients in Fe–Ga alloys: A case study by a tracer-diffusion couple method

“…The minor difference in results is evident because of the very small deviation of the molar volume in this system. A higher difference can be found in other systems depending on the extent of departure of the molar volume from the ideality [34]. It also should be noted here the similarities of interdiffusion coefficients when estimated from different incremental diffusion couples.…”

A Mystery of "Sluggish Diffusion" in High-Entropy Alloys: The Truth or a Myth?

“…Combining Equations ( 3) and (4a)-(4c), one can estimate the composition dependent interdiffusion coefficients from a single diffusion couple over the whole composition profile. Additionally at the Kirkendall marker plane, one can estimate the intrinsic diffusion coefficients following [42]…”

Techniques of Tracer Diffusion Measurements in Metals, Alloys and Compounds

“…In a binary system, we have [1]. The growth mechanism of the phases was explained based on such analysis extensively in various systems [86,87,88,89,90,91]. The tracer diffusion coefficients estimated following the radiotracer [92] and diffusion couple method [93] were found to be comparable in the Mo-Si system.…”