Effect of annealing temperature on structure and high-temperature soft magnetic properties of (Fe0.9Co0.1)72.7Al0.8Si13.5Cu1Nb3B8V1 nanocrystalline alloy
Graphical abstract
Introduction
Soft magnetic materials occupy an important position in magnetic materials and are widely used in engineering technology fields such as power, electronic communications, aerospace, and computer technology. Nanocrystalline alloy is a new material developed based on the amorphous alloy. The first nanocrystalline material was discovered by Y. Yoshizawa et al. in 1988 [1]. The typical composition of this material is Fe73.5Cu1Nb3Si13.5B9, which is called FINEMET. The excellent soft magnetic properties of this material are shown as high saturation magnetic induction, high permeability, low coercivity, and low hysteresis loss. Studies have shown that the Curie point of Fe-based nanocrystalline alloys is relatively low, and the soft magnetic properties sharply deteriorate above 300 °C [[2], [3], [4], [5]], so the application of FINEMET is usually limited below 300 °C [6]. In 1991, Suzuki et al. first discovered Nanoperm type alloys, whose typical composition is Fe88Zr7B4Cu1 [7]. Although these alloys have higher saturation magnetic induction (1.63 T), the coercivity (5.8 A/m) and the loss of these alloys are higher than those of Finemet alloys. The Curie temperature of the amorphous phase of Nanoperm alloy is only slightly higher than room temperature, and its excellent soft magnetic properties are lost under a high-temperature environment [2,3]. In 1996, M. Müller et al. [8] first proposed the Fe-Co-M-B-Cu (M = Nb, Zr, Hf) type alloy, and its typical composition is Fe44Co44Zr7B4Cu1. The alloy can work at temperatures up to 600 °C. Co can increase the Curie temperature while Co enhances the coercivity (Hc) of the material and reduces the permeability (μi) [9]. At the same time, the excess Co will increase the saturation magnetostriction and anisotropy, thereby increasing the loss (W) of the alloy [10]. Therefore, we will add a small amount of Co into Finemet to improve soft magnetic properties. It was reported that doping Al in Fe-based alloy can reduce magnetic anisotropy K1, as the K1 of FeSiAl crystals is lower than that of the binary FeSi system [11]. In general, partial substitution of Fe by Al could reduce the effective magnetocrystalline anisotropy K and saturation magnetostriction λS, which is advantageous for achieving outstanding soft magnetic properties [12]. Recent studies have shown that Fe(Co)AlCuNbBCu alloys exhibited excellent soft magnetic properties at room- and high-temperatures [13,14]. Furthermore, the core loss of the V doped ribbon has been reported to be much lower than that of pure Finemet at different frequencies in the range of 1 kHz [15]. Hence, we designed (Fe0.9Co0.1)72.7Al0.8Cu1Nb3Si13.5B8V1 alloy to further improve soft magnetic properties at elevated temperatures.
In the present paper, we mainly concentrate on studying the correlation between the microstructure and high-temperature soft magnetic properties by changing the annealing temperature and analyzing the mechanism of improving high-temperature magnetic properties based on exchange coupling and effective anisotropy models.
Section snippets
Experimental procedure
Amorphous (Fe0.9Co0.1) 72.7Al0.8Cu1Nb3Si13.5B8V1 alloy ribbon, with a width and thickness of approximately 2 mm and 25 μm respectively, are prepared by a melt spinning technique under Ar atmosphere at a roll speed of 4000 r/min and a linear speed of 28 m/s. The amorphous ribbon is wound into a ring-shaped sample with an outer diameter of approximately 18 mm and an inner diameter of 16 mm for measuring the initial permeability. Thermal analysis for as-quenched alloy was performed by differential
Results and discussion
Fig. 1 shows the DSC curve of as-quenched amorphous (Fe0.9Co0.1) 72.7Al0.8Si13.5Cu1B8V1 alloy. It can be seen that the amorphous alloy during the continuous heating has two exothermic peaks, which correspond to the primary crystallization (Tx1 = 502 °C) for precipitating soft magnetic crystalline phase of α-Fe(Co, Si) and secondary crystallization (Tx2 = 697 °C) for forming hard magnetic phase of Fe-borides compounds [16,17], respectively.
Fig. 2 shows the XRD of (Fe0.9Co0.1)72.7Al0.8Si13.5Cu1Nb3
Conclusions
The effects of different annealing temperatures on the structure and high temperature soft magnetic properties of nanocrystalline (Fe0.9Co0.1)72.7Al0.8Si13.5Cu1Nb3B8V1 alloy are investigated. The μi-T curves of the alloy were measured after vacuum annealing at 510 °C, 550 °C, 590 °C, 630 °C and 690 °C. As the annealing temperature (Ta) increases, the volume fraction of the crystalline phase Vcry increases from 58 % (Ta = 510 °C) to 89 % (Ta = 630 °C) and the amorphous layer thickness
CRediT authorship contribution statement
Yan Zhang: Conceptualization, Methodology, Software, Writing - original draft. Zhi Wang: Resources, Writing - review & editing, Supervision, Project administration. Xian-hua Li: Validation, Investigation. Qian-qian Hao: Validation, Investigation. Rui-min Shi: Software, Formal analysis.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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