| FeCo-based nanocrystalline soft magnetid materials have perfect magnetics, such as high permeability, high magnetic induction intensity, low coercive force, low dissipation and so on. They are best promising for the more-electric aircraft(MEA) and other high-temperature application ateas. Therefore, the research on the formation and properties of it has attracted widespread attention in recent years. In this paper, We use lots of research methods, such as X-ray diffraction, Mossbauer spectroscopy, Transmission electron microscopy and Differential Scanning Calorimetry to resrarch microstructure, stability and soft magnetic properties of (Fe1-xCox)86Hf7B6Cu1(x=0.4) alloy. The followings are details:1. Chemical constituents of (Fe1-xCox)86Hf7B6Cu1(x=0.4) alloys were designed in this articale. By melting the master alloy for4-5times to ensure to get homogeneous master alloys. Used the single roller quenching method to obtain the amorphous thin strip.2. The samples were analyzed by X-ray diffraction(XRD), and the results indicated that they all had amorphous packets which confirmed the samples could be complete amorphous. The transmission electrical microscopy(TEM) analysis indicated that the diffraction rings of (Fe1-xCox)86Hf7B6Cu1(x=0.4) were dispersed cyclic structure, and the pattern of the matrix was homogeneous. It could prove that they were in amorphous state. Mossbauer spectroscopy (MS) analysis indicated the as-quenched alloy presented a typical broadened and overlapped sextet, and the second and fifth peaks were higher than the first and the sixth peaks obviously, which confirmed amorphous state.3. The amorphous thin ribbons were treated by middle-frequency magnetic pulsing: pulse magnetic field from100Oe to250Oe, processing time from10-30min and pulse frequency from1500-2000Hz. The results of X-ray, MS and TEM experiments show that middle-frequency magnetic pulsing treatment can achieve single-phase nanocrystallization of (Fe1-xCox)86Hf7B6Cu1(x=:0.4) amorphous alloy. During crystallization processes, the mean size of10-15nm nanocrystalline phase a-Fe(Co) is born and dispersed in the residual amorphous matrix phase to form the so-called two-phase nanocrystalline alloys. Under the different treatment conditions, the volume fraction of the crystallization is change in the range of11.21%～42.06%. With the increasing of the pulse magnetic field or the processing time, the amount of the crystallization presents are increasing trentency. When other conditions are same, the crystallization rate of2000Hz frequency is higher than1500Hz frequency.Used DSC to measure the samples before and after treated by pulsing. There were three exothermic peaks on the DSC curve. The three crystallization enthalpy of quenched sample were51.48J/g,60.19J/g and19.32J/g, while the enthalpy of sample A6(H=250Oe, T=20min, f=2000Hz) were65.86J/g,106.4J/g and6.113J/g. They were higher than the quenched samples. This indicates that the thermal stability of nanocrystalline two-phase alloys increase slightly compared with the quenched alloys.4. The original samples and the samples after the magnetic pulse treatment were measured by Vibrating Sample Magnetometer(VSM). The results showed that the samples after low frequency magnetic pulse treatment had higher saturation magnetization and smaller coercivity. The best soft magnetic properties was obstained at the condition of magnetic field strength200Oe, frequency2000Hz, the acting time10min. At this time, Hc=0.42172g, Bs=174.59emu/g. When the crystallization is small, magenetic optimization is not obvious. When the crystallization reaches about25%, the coercivity is significantly reduced. This means that durning the process of middle-frequency magnetic pulsing treatment, the structure of the alloys became more ordering, and the elimination of structural defects were more fully. However, the relationship between the selection of magnetic pulse parameters and magnetic properties have yet to be studied further. |
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