Diffusion in high entropy alloys: Development and application of an experiment-ab initio approach
Final Report Abstract
Reliable control over phase decomposition and creep behavior of high entropy alloys (HEAs) poses enormous challenges from both the theoretical as well as the experimental side in view of the multiprincipal element nature of these alloys and their presumably slow diffusion. The present project DIFFINITIO successfully tackled these challenges via the development and application of an integrated experiment-ab initio approach for the determination of accurate diffusion coefficients in hexagonal close-packed (HCP) HEAs as a case study. The project unified the leading and unique expertise of the applicants in the fields of the radiotracer diffusion measurements and finite temperature ab-initio computations. As a result, we have provided fundamental insights into the diffusion properties of HEAs. We have discovered unexpected phenomena, specifically of "anti-sluggish” self-diffusion and "ultra-fast” diffusion of solutes in these HCP HEAs. For the first time, the experimental results unambiguously verified that diffusion in HEAs is not necessarily sluggish as it was advocated in the early stages of the HEA research, mainly on an arbitrary basis. Our finding prompts for a paradigm change, especially in view of the absence of any "sluggishness” of diffusion in body-centered cubic HEAs, likewise discovered in the framework of the present project. The ab-initio informed calculations revealed the impact of local atomic distortions on the relative rates of atomic diffusion in the multiprincipal element alloys. The theoretical predictions were verified by measuring Sc diffusion in these alloys. Moreover, the concept of using Zn as an Al substitute in Al-containing alloys has been intensively examined using density-functional-theory (DFT) calculations and the understanding of diffusion properties of all constituting elements in HCP HEAs has been elaborated. DFT-based barrier calculations have been performed and the cluster expansion-based kinetic Monte Carlo simulations allowed us a direct quantification of the correlation and short-range ordering effects.
Publications
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Phenomenon of ultra-fast tracer diffusion of Co in HCP high entropy alloys. Acta Materialia, 196, 220-230.
Vaidya, Mayur; Sen, Sandipan; Zhang, Xi; Frommeyer, Lena; Rogal, Łukasz; Sankaran, S.; Grabowski, Blazej; Wilde, Gerhard & Divinski, Sergiy V.
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Ab initio prediction of vacancy energetics in HCP Al-Hf-Sc-Ti-Zr high entropy alloys and the subsystems. Acta Materialia, 227, 117677.
Zhang, Xi; Divinski, Sergiy V. & Grabowski, Blazej
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High-Entropy Alloys: Diffusion. Encyclopedia of Materials: Metals and Alloys (2022), 402-416. American Geophysical Union (AGU).
Divinski, Sergiy V.; Lukianova, Olga A.; Wilde, Gerhard; Dash, Anuj; Esakkiraja, Neelamegan & Paul, Aloke
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Recent Advances in Understanding Diffusion in Multiprincipal Element Systems. Annual Review of Materials Research, 52(1), 383–409
Dash, Anuj; Paul, Aloke; Sen, Sandipan; Divinski, Sergiy; Kundin, Julia; Steinbach, Ingo; Grabowski, Blazej & Zhang, Xi
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Zr diffusion in BCC refractory high entropy alloys: A case of ‘non-sluggish’ diffusion behavior. Acta Materialia, 233, 117970.
Grabowski, and Xi Zhang
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Does Zn mimic diffusion of Al in the HCP Al-Sc-Hf-Ti-Zr high entropy alloys?. Scripta Materialia, 229, 115376.
Sen, Sandipan; Zhang, Xi; Rogal, Lukasz; Wilde, Gerhard; Grabowski, Blazej & Divinski, Sergiy V.
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‘Anti-sluggish’ Ti diffusion in HCP high-entropy alloys: Chemical complexity vs. lattice distortions. Scripta Materialia, 224, 115117.
Sen, Sandipan; Zhang, Xi; Rogal, Lukasz; Wilde, Gerhard; Grabowski, Blazej & Divinski, Sergiy V.
