Microstructural Transitions in Commercial Fe-Ni–Based Soft-Magnetic Alloys Quenched from Undercooled Liquid Droplets

Liquid droplets of three commercial Fe-Ni – based alloys were undercooled to different temperatures by electromagnetic levitation and quenched. Discontinuous changes in the grain size and microstructure as a function of melt undercooling (Δ T ) were observed in all three alloys. At Δ T  < 80 K, f...

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Published inMetallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 39; no. 12; pp. 2906 - 2913
Main Authors Woodcock, T.G., Shuleshova, O., Gehrmann, B., Löser, W.
Format Journal Article
LanguageEnglish
Published Boston Springer US 01.12.2008
Springer
Springer Nature B.V
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Summary:Liquid droplets of three commercial Fe-Ni – based alloys were undercooled to different temperatures by electromagnetic levitation and quenched. Discontinuous changes in the grain size and microstructure as a function of melt undercooling (Δ T ) were observed in all three alloys. At Δ T  < 80 K, fine, equiaxed grains with a substructure consisting of spherical elements were observed. In the range 80 K < Δ T  < 155 K, the microstructure consisted of colonies of columnar dendrites. The colonies were two orders of magnitude larger than the equiaxed grains reported at lower Δ T. At Δ T  > 155 K, the equiaxed grains with a substructure of spherical elements returned. The critical undercoolings at which the microstructural transitions occur (Δ T * 1  = 80 K and Δ T * 2  = 155 K) show good agreement with those for similar binary systems. The results were successfully described by calculating the time needed for breakup of the primary dendrites as a function of Δ T and comparing this to the time during which the sample temperature is above the solidus due to recalescence.
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ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-008-9635-x