Dual-Cluster Characteristic and Composition Optimization of Finemet Soft Magnetic Nanocrystalline Alloys

Yaoxiang Geng, Xin Lin, Jianbing Qiang, Yingmin Wang, Chuang Dong

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Abstract

The development of nanocrystalline Fe-Si-B-Nb-Cu alloys, commercially known as Finemet, has established a new approach to obtain soft-magnetic materials with high magnetic flux density. The material consists of α-Fe(Si) nanocrystals embedded in an amorphous matrix, which is made by means of partial crystallization. The composition and local structure of the precursor amorphous alloys are crucial for the formation of the unique nanocrystalline structure. The present study is devoted to understanding the composition characteristics and developing new compositions of Finemet alloys. Using the"cluster-plus-glue-atom"model and noticing the crystallization characteristic of Finemet alloy, a"dualcluster"amorphous structure model is proposed. In this model, the precursor amorphous structure of Finemet alloy is considered to contain a mixture of the [(Si, B)-B2(Fe, Nb)8]Fe cluster derived from the FeB-Si-Nb bulk glassy alloys, and the [Si-Fe14] (Cu1/13Si12/13)3 cluster from Fe3Si phase. A series of new Finemet nanocrystalline alloy compositions are designed by mixing [(Si, B)-B2(Fe, Nb)8]Fe and [Si-Fe14] (Cu1/13Si12/13)3 cluster formulas with a ratio of 1: 1. Thermal analysis results show that [(Si0.8B0.2)-B2Fe7.2Nb0.8] Fe+[Si-Fe14](Cu1/13Si12/13)3 (alloy composition: Fe74B7.33Si15.23Nb2.67Cu0.77) amorphous alloy exhibits a maximal temperature interval of about 192 K between the first and second crystallization peaks. Magnetic measurement results show that the Fe74B7.33Si15.23Nb2.67Cu0.77 nanocrystalline alloy exhibits optimal soft magnetic properties with a saturation magnetization Bs about 1.26 T, a coercive force Hc about 0.5 A/m and an effective permeability me about 8.5×105 at 1 kHz after isothermal annealing at 813 K for 60 min. The soft magnetic properties of the new composition nanocrystalline alloys are better than that of the typical Finemet nanocrystalline alloy (Fe73.5Si13.5B9Cu1Nb3).

Original languageEnglish
Pages (from-to)833-841
Number of pages9
JournalJinshu Xuebao/Acta Metallurgica Sinica
Volume53
Issue number7
DOIs
StatePublished - 11 Jul 2017

Keywords

  • "dual-cluster"model
  • Composition design
  • Finemet nanocrystalline alloy
  • Soft magnetic property

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