Demystifying the sluggish diffusion effect in high entropy alloys

• Published in: Journal of alloys and compounds Vol. 783; pp. 193 - 207
• Main Authors: Dąbrowa, Juliusz, Zajusz, Marek, Kucza, Witold, Cieślak, Grzegorz, Berent, Katarzyna, Czeppe, Tomasz, Kulik, Tadeusz, Danielewski, Marek
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 30.04.2019; Elsevier BV
• Subjects: Alloy systems; Aluminum; Binary systems; Chromium; Cobalt; Computer simulations; Diffusion; Diffusion effects; High entropy alloys; Interdiffusion; Iron; Manganese; Melting points; Nickel; Optimization; Temperature; Ternary systems; Thermodynamic modeling; Tracer diffusion; High entropy alloys; Thermodynamic modeling; Diffusion; Computer simulations
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.12.300

Interdiffusion studies in Co-Cr-Fe-Mn-Ni, Co-Fe-Mn-Ni, Co-Cr-Fe-Ni, and Co-Cr-Mn-Ni, as well as a reevaluation of the previous results obtained for Al-Co-Cr-Fe-Ni, were conducted. In the experimental part, diffusion couples were annealed at four different temperatures: 1230, 1270, 1310 and 1350 K for each system. Then, the results were evaluated with use of the optimization-based technique, combined with the Miedema's thermodynamic description, what allowed obtaining of tracer diffusion coefficients for all elements in all considered systems. The correctness of the applied approach was tested on the example of Co-Cr-Fe-Mn-Ni system, showing very good agreement of determined tracer diffusivities with the values obtained by other authors. Obtained values of diffusivities were compared with the available data for a number of conventional binary and ternary systems. No signs of diffusion retardation were observed in the absolute temperature scale. In the case of temperature scale normalized with respect to the melting point, an abnormal behavior, previously attributed to the HEAs' sluggish diffusion effect was observed. However, it occurred only for alloys with prominent manganese content and was completely independent of the number of components, being just as likely to occur in binary systems as in HEAs. Therefore, the alleged sluggishness of diffusion in HEAs should be treated just as a result of specific compositions of the previously studied alloys and cannot be generalized for all high entropy systems. [Display omitted] •Diffusion was studied in Co-Cr-Fe-Mn-Ni, Co-Fe-Mn-Ni, Co-Cr-Fe-Ni, and Co-Cr-Mn-Ni.•Results for Al-Co-Cr-Fe-Ni were reevaluated.•Diffusion couples were evaluated with use of the optimization-based technique.•The observed sluggishness of diffusion was correlated with presence of Mn.•The observed sluggishness was independent of number of components.