| With the increasingly serious of global warming and energy shortage, energy consumption has become a major global research. In recent years, our government has also developed a number of policies to promote and encourage the development and promotion of energy-saving technologies. Soft magnetic materials are widely used in the manufacture of various key components of energy conversion in power and electronics applications. Therefore, high saturation magnetic flux density and low-loss soft magnetic materials have great value both in the high frequency or low frequency applications in the field of power and electronics. The application of high-performance soft magnetic materials can not only improve the energy conversion efficiency and reduce the volume of equipment, but also reduce the consumption of resources at the same time.With the development of materials science, composite structural materials reflect more and more advantages in practical applications. The composite structural materials can be suitable for the application under different situations through the changes of multi-phase ratio and the diversity of morphology. The amorphous/ nanocrystalline soft magnetic alloys and magnetic powder cores are typical composite structural materials in soft magnetic materials. In recent years, these two types of soft magnetic materials have made great progresses in performance adjustability and application stability with the tireless efforts of researchers.The amorphous/nanocrystalline soft magnetic materials attracted much attention with its excellent magnetic properties and low prices. Such a soft magnetic material having the advantages of high permeability and saturation flux density, low coercivity and loss, good frequency characteristics, etc. It is recognized as the world’s best overall performance of soft magnetic material. The cobalt-based amorphous and iron-based amorphous has been replaced by the amorphous/nanocrystalline soft magnetic materials in many areas for a variety of electrical and electronic components in the present situation. However, the research period of the amorphous /nanocrystalline soft magnetic materials is relatively short compared to other other conventional soft magnetic materials. A lot of work still needed to further clarify the optimization of technology and formulations of the amorphous/nanocrystalline soft magnetic materials.Unlike the amorphous/nanocrystalline soft magnetic alloys, magnetic powder core is a kind of soft magnetic composite which produced by powder metallurgy process with soft magnetic powders after insulating coating. The magnetic powder cores have advantages of low-loss under high-frequency applications, good thermal stability, small permeability changes in frequency altering, high saturation flux density and wide permeability constant region. The permeability of magnetic powder core can be modified through the proportion of the insulating medium and soft magnetic powder to adjust the performance of the various applications also. And it is widely used in electrical switches, choke coils, high-precision instruments and equipment voltage vessels. However, the performance of the magnetic powder cores is affected by powder particle size, molding pressure and the type and content of insulating binder. The heat treatment temperature also played an important role. The improved preparation process and detailed preparation method are the key technology and core issues for the preparation of magnetic powder cores.In this paper, a systematic study on the preparation and properties of the composite structural soft magnetic materials was started with the amorphous/ nanocrystalline soft magnetic alloys. RE element(Y, Gd, Tb and Dy) substitutions(2at%) of Fe have dramatic effects on the microstructure, thermal stability, crystallization behavior and magnetic properties of the melt spun Fe82.65Cu1.35Si2B14 alloys. In detail, RE additions significantly improve the amorphous forming ability and thermal stability of the alloys. The primary crystallization temperatures are increased for at least 55°C. RE additions also change the crystallization behavior by the precipitation of a steady metastable Fe3 B phase. For Fe80.65Cu1.35Si2B14Gd2 alloy, the Fe3 B phase can be stably exist even the temperature rise up to 600°C. The Curie temperature(Tc) and magnetic moment for Gd, Tb, Dy doped alloys are significantly lower than Y doped and without doping alloys may due to the RE-Fe antiferromagnetic coupling in amorphous matrix. The addition of Y is found to be beneficial for the soft magnetic application of the alloy. The saturation flux density and coercivity for Fe80.65Cu1.35Si2B14Y2 alloy after 60 min annealing under 450°C are 1.80 T and 6.5A/m, respectively.In order to examine the application of nanocrystalline soft magnetic alloy under high temperature environment, typical HITPERM type Fe44Co44Zr7B4Cu1 alloy was targeted studied. Five kinds of alloying elements, Y, Si, Al, Nb and Ti, were added into Fe44Co44Zr7B4Cu1 alloy with atomic percentage of 2%. The effects of the element additions on the microstructure, thermal stability, crystallization behavior and magnetic properties were systematically investigated. The results show that the as-quenched state of(Fe44Co44Zr7B4Cu1)98M2 alloys remain amorphous with the addition of the alloying elements, but the thermal stability of the alloy there are significantly changed. Among the addition elements, Si and Nb increased the secondary crystallization temperature of the alloys most significantly. The secondary crystallization temperature was increased up to 710°C, the alloys can maintain a stable structure after 1 hour heat treatment in a wide temperature range from 500°C to 650°C. The addition of Si not only efficiently increased the soft magnetic applications of the alloy, but also reduced the cost. There is no obvious growth of the grains in(Fe44Co44Zr7B4Cu1)98Si2 alloys after 300 hours annealing under 550°C compared to 1 hour annealing sample. The grain size is ~15nm. But the coercivity of the two sample are much different. The coercivity of 1 hour annealed sample is 50A/m, while the 300 hours annealed sample is 200A/m. Through the Energy Dispersive Spectrometer(EDS) analysis, it was found that the segregation of Si and Cu atoms occurs with the increasing time of heat treatment which lead to the increasing of coercivity.The magnetic powder cores, as another type of composite structural soft magnetic materials, have been systematically investigated also. In this paper, the preparation process and soft magnetic properties of Fe-Si-B amorphous powder cores and Fe-Si-Al powder cores are detailed studied, and an improved preparation technology was obtained.In order to optimize the performance properties and the preparation process of Fe-Si-B amorphous powder cores, the properties of Fe-Si-B powder cores are investigated with altering the molding pressure, insulating binder content and types of inorganic additives in insulating binder. The results show that with the increasing of molding pressure, the permeability(μe) of powder cores increased while the loss(P) reduced. With the increasing of the insulating binder content, the μe and P are both reduced. In the case of the same insulating binder content, the powder cores with complex addition of Kaolin and α-Al2O3 obtained the best alternating current(AC) application performance compare to the simple Kaolin and α-Al2O3 addition. The performance of the Fe-Si-B amorphous powder cores can be effectively changed by altering the molding pressure, the insulating binder content and composition. The Fe-Si-B amorphous powder core manufactured with a molding pressure of 1600 MPa, insulating binder content of 7wt%, insulating binder composition containing silicone resin, Kaolin and α-Al2O3 and annealed under 400°C, the μe and P(at 100 kHz, Bm=50mT) are 28 and 44.3W/kg, respectively.With the prior studies of Fe-Si-B amorphous powder cores, we selected the molding pressure of 1600 MPa in the followed studies of Fe-Si-Al powder cores. It was found that the insulating binder content, insulating binder composition and particle size distribution of the magnetic powders in the preparation process can significantly influence the performance FeSi-Al powder cores. The results show that with the increasing of the insulating binder content, the μe and P of Fe-Si-Al powder cores are both reduced. In the case of the same insulating binder content, inorganic additives of Kaolin and α-Al2O3 added in the insulating binder can effectively improve the application performance of powder cores. In the condition of using magnetic powders without sieving,the core manufactured with insulating binder content of 7wt% and insulating binder composition containing silicone resin, Kaolin and α-Al2O3 obtained the highest μe of 60, while the P is 25.2W/kg(at 100 kHz, Bm=50mT). And the core manufactured with insulating binder content of 7wt% and insulating binder composition containing silicone resin, Kaolin and α-Al2O3 obtained lowest P of 18.7W/kg(at 100 kHz, Bm=50mT), while the μe is 45. With the sieving of original magnetic powders, the larger particle size of the magnetic powder was used, the higher of μe and P were obtained. The Fe-Si-Al powder core manufactured with particle size less than 50μm, insulating binder content of 7wt%, insulating binder composition containing silicone resin, Kaolin and α-Al2O3 obtained lowest P and μe are 14.0W/kg(at 100 kHz, Bm=50mT) and 40, respectively. |
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