Analysis of diffusion in high entropy alloys

High-entropy alloys (HEAs) are a class of multicomponent alloys consisting of five or more principal elements with equal (or nearly equal) compositions. Diffusion plays an important role in these alloys and, indeed, if diffusion is rather sluggish, it may be partly responsible for the apparent stability of HEAs. For the understanding of diffusion properties of HEAs, the full diffusion kinetics behaviour of self-diffusion and interdiffusion in HEAs needs to be investigated. This problem is addressed in this paper by extending and applying three diffusion kinetics formalisms, one due to Darken, a combination of one from Manning and one from Holdsworth and Elliott (HE), and a 'light' version of one due to Moleko, Allnatt and Allnatt. Recently, an elegant and novel quasi-binary variation of a standard experimental interdiffusion set-up was used in a study of diffusion in a CoCrFeMn0.5Ni alloy [1, 2]. We successfully address these quasi-binary interdiffusion experiments analytically by applying the above random alloy diffusion kinetics formalisms for the case of CoCrFeMn0.5Ni in order to extract self-diffusion coefficients. This success now suggests that the quasi-binary variation of a standard interdiffusion set-up should be used more widely for diffusion studies in multicomponent alloys, especially HEAs.