Invar effects in FeNiCo medium entropy alloys: From an Invar treasure map to alloy design

Ziyuan Rao, Dirk Ponge, Fritz Körmann, Yuji Ikeda, Oldřich Schneeweiss, Martin Friák, Jörg Neugebauer, Dierk Raabe, Zhiming Li*

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    23 Citations (Scopus)
    162 Downloads (Pure)

    Abstract

    To facilitate the understanding of Invar effects and design of FeNiCo-base Invar alloys characterized by low thermal expansion coefficient (TEC), we investigated the magnetic and thermal expansion behavior of an equiatomic prototype medium entropy alloy FeNiCo and a non-equiatomic (super Invar)Fe63Ni32Co5 (at. %)reference alloy by means of experiments and ab initio calculations. Both alloys consist of a single face-centered cubic phase with fully recrystallized microstructure in the homogenized state. Large spontaneous volume magnetostriction is observed in both alloys below their respective Curie temperatures. The Invar effect in the non-equiatomic Fe63Ni32Co5 alloy is of step-type with nearly zero TEC over a wide temperature range (from room temperature to 120 °C)below its Curie temperature. The equiatomic FeNiCo alloy shows a peak-type Invar effect in a very narrow temperature range (from ∼675 °C to ∼730 °C)with relatively low TECs. The equiatomic FeNiCo alloy shows both higher saturation magnetization and Curie temperature than the non-equiatomic Fe63Ni32Co5 alloy. The relationships among magnetic behavior, spontaneous volume magnetostriction and Invar effects for a wider array of metallic alloys are discussed mainly based on Masumoto's rule combined with Wohlfarth's itinerant electron theory. An Invar alloy search map is constructed based on the present results and available literature data to visualize the relationships among saturation magnetization, Curie temperature and thermal expansion coefficient for a wide range of Invar alloys. Based on this treasure map a design route for further developments of new Invar alloys by tuning their magnetic properties is discussed.

    Original languageEnglish
    Article number106520
    Number of pages11
    JournalIntermetallics
    Volume111
    DOIs
    Publication statusPublished - 2019

    Bibliographical note

    Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care

    Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

    Keywords

    • Ab initio
    • Invar effect
    • Magnetic properties
    • Medium entropy alloys
    • Spontaneous volume magnetostriction

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