Murugaiyan, Premkumar and Bedanta, Subhankar and Jena, Sukanta Kumar and Panda, Ashis K and Mitra, Amitava and Bysakh, Sandip and Roy, Rajat K (2020) Crystallization and magnetic hardening behaviour of Fe-rich FeSiBNb(Cu) melt-spun alloys. Journal of Magnetism and Magnetic Materials, 502. Art No-166528. ISSN 0304-8853

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The sequential, multi-stage crystallization and magnetic hardening behaviour of Fe82B14Si2Nb2, Fe83B13Si2Nb2, Fe83B12Si2Nb2Cu1 and Fe85B13Nb2 melt-spun alloys have been investigated. The microstructure-crystallization-magnetic property relationship was established using X-ray diffractometry (XRD), differential scanning calorimetry (DSC), magnetometry, transmission electron microscopy (TEM) and magneto-optical Kerr effect microscopy (MOKE) techniques. The increase of Fe content (> 82 at%) of as-quenched ribbons imparts microstructural heterogeneity across the ribbon cross-section; i.e., textured alpha-Fe crystals at the free surface to heteroamorphous microstructure in the bulk matrix. The isochronal annealing of hetero-amorphous alloys depicts simultaneous surface and bulk crystallization process occurring before and after the crystallization onset temperature (T-x1) temperature. The annealing temperature range (T-a < T-x1) coinciding with the paramagnetic region of the thermo-magnetic plot, induces irreversible magnetic hardening due to simultaneous coarsening of pre-existing crystal nuclei and exchange de-coupling between nanocrystal and intergranular matrix. The onset of primary crystallization in the pre-crystallized ribbons results in bimodal nanocrystallite distribution having an average crystallite size exceeding the ferromagnetic exchange length of Fe-based alloys. The minor Cu addition alters the growth morphology of pre-existing nuclei from dendrite-like to equiaxed, assisting heterogeneous nucleation and improving intergranular amorphous stability by delaying boride precipitation. The soft-magnetic property deterioration of partially crystallized ribbons is discussed within the framework of Extended-Random Anisotropy models.

Item Type: Article
Subjects: Engineering Materials
Depositing User: Bidhan Chaudhuri
Date Deposited: 05 Feb 2021 11:19
Last Modified: 05 Feb 2021 11:19

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