Invar effects in FeNiCo medium entropy alloys

From an Invar treasure map to alloy design

Journal article (2019)

Authors

Ziyuan Rao Max-Planck-Institut für Eisenforschung
Dirk Ponge Max-Planck-Institut für Eisenforschung
F.H.W. Körmann (OLD) MSE-7 , Max-Planck-Institut für Eisenforschung
Yuji Ikeda Max-Planck-Institut für Eisenforschung
Oldřich Schneeweiss Czech Academy of Sciences
Martin Friák Czech Academy of Sciences
Jörg Neugebauer Max-Planck-Institut für Eisenforschung
D. Raabe Max-Planck-Institut für Eisenforschung
Zhiming Li Max-Planck-Institut für Eisenforschung
Research Group
(OLD) MSE-7
Copyright: © 2019 Ziyuan Rao, Dirk Ponge, F.H.W. Körmann, Yuji Ikeda, Oldřich Schneeweiss, Martin Friák, Jörg Neugebauer, Dierk Raabe, Zhiming Li
DOI
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https://doi.org/10.1016/j.intermet.2019.106520
Ab initio Magnetic properties Invar effect Medium entropy alloys Spontaneous volume magnetostriction
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Published Date

2019

Language

English

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Research Group

(OLD) MSE-7

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.