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

• Published in: Metallurgical 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
• Language: English
• Published: Boston Springer US 01.12.2008; Springer; Springer Nature B.V
• Subjects: Alloys; Applied sciences; Changes; Characterization and Evaluation of Materials; Chemistry and Materials Science; Exact sciences and technology; Experiments; Grain size; Magnetic fields; Materials Science; Metallic Materials; Metallurgy; Metals. Metallurgy; Nanotechnology; Radio frequency; Structural Materials; Surface tension; Surfaces and Interfaces; Thin Films; Velocity; Substructure Element; Electromagnetic Levitation; Columnar Dendrite; Microstructural Transition; Breakup Time; Nickel base alloys; Magnetic alloy; Heat treatment; Magnetic material; Droplet; Microstructure; Quenching
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-008-9635-x

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.