Direct Formation of Hard-Magnetic Tetrataenite in Bulk Alloy Castings

Yurii P. Ivanov, Baran Sarac, Sergey V. Ketov, Jürgen Eckert, A. Lindsay Greer

Research output: Contribution to journalArticleResearchpeer-review


Currently, predominant high-performance permanent magnets contain rare-earth elements. In the search for rare-earth-free alternates, body-centered tetragonal Fe–Ni is notable. The ordering to form this phase from the usual cubic close-packed Fe-Ni is understood to be possible only below a critical temperature, commonly accepted to be 593 K. The ordering is first demonstrated by using neutron irradiation to accelerate atomic diffusion. The tetragonal phase, designated as the mineral tetrataenite, is found in Fe-based meteorites, its formation attributed to ultra-slow cooling. Despite many attempts with diverse approaches, bulk synthesis of tetrataenite has not been reported. Here it is shown that with appropriate alloy compositions, bulk synthesis of tetrataenite is possible, even in conventional casting at cooling rates 11‒15 orders of magnitude higher than in meteorites. The barrier to obtaining tetrataenite (slow ordering from cubic close-packed to body-centered tetragonal) is circumvented, opening a processing window for potential rare-earth-free permanent magnets. The formation of tetrataenite on industrially practicable timescales also throws into question the interpretation of its formation in meteorites and their associated cooling rates.
Original languageEnglish
Article number2204315
Number of pages8
JournalAdvanced science
Issue number1
Early online date25 Oct 2022
Publication statusPublished - 4 Jan 2023

Bibliographical note

Publisher Copyright: © 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.


  • meteorite
  • order-disorder
  • rare-earth-free permanent magnet
  • tetrataenite

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