Effect of alloy substituents on soft magnetic properties and economics of Fe-based and Co-based alloys
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Amorphous and nanocrystalline soft magnetic alloys have garnered interests in academia and industry due to their potentials for applications, such as power transformers, electric motors, and sensors. To achieve good glass formability, thermal stability, and prevent grain overgrowth, elements such as B, Nb, Ta, and Hf are used in many soft magnetic systems. However, the high price of these precursors results in expensive soft magnetic alloys. Herein, we report on substituting Ta and Hf with TaC and HfC, respectively, to significantly reduce the cost of Fe-based FINEMET and Co-based HTX005 alloys. Soft magnetic properties of these alloys are studied. The effect of thermal annealing and strain annealing on TaC and HfC substituted alloys are also investigated. Lastly, we discuss the cost analysis on these alloys. Using the synthesis route presented here, a cost reduction of up to 74% can be achieved.
I. INTRODUCTION
In recent years, many amorphous and nanocrystalline soft magnetic alloys have been developed for a wide range of applications, which include power transformers, magnetic shielding, electric motors, magnetic field sensors, etc.1–7 In the synthesis of these alloys, early transition metals (e.g., Nb, Ta, and Hf) and glass formers (e.g., B, Si, and Al) are used to improve glass formability and prevent overgrowth of the grains.8–12 However, precursors such as B, Nb, Ta, and Hf are expensive and make up for more than 70% of the total alloy cost despite their low concentrations.13–15 Attempts to reduce the alloy cost include the development of B-free alloys and substitution of B with B4C. Previously, Long et al. reported on the development and studies of structural and soft magnetic properties of a B-free Fe-based alloy.16 In his work, Si and Zr were used as growth inhibitors to result in soft magnetic alloy with ;10 grain size and 19 W/kg power loss, comparable with the typical power loss of FINEMET alloys. Kopcewicz et al. have also studied this B-free system.13,15 In his report, x-ray diffraction and Moessbauer spectroscopy measurements were used to reveal the amorphous structure of the melt-spun soft magnetic ribbons. Okumura Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/jmr-editor-manuscripts/. DOI: 10.1557/jmr.2015.197 J. Mater. Res., Vol. 30, No. 14, Jul 28, 2015
et al. and Zabransky and Jiraskova have explored the idea of substituting B with the significantly cheaper Si and studied the structural and soft magnetic properties of Sirich FINEMET alloys.17,18 Ramanan and Fish and Donald and Davies investigated the substitution of B with other metalloids and its effects on the onset of crystallization of the materials.19,20 Kurniawan et al. studied the effect of substitution of B with B4C on the soft magnetic properties of Co-based alloys.21 While t
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