Formation And Magnetic Pulsing Effect Of High Temperature Soft Magnetic Fe(co)-hf-b-cu Alloys

Iron-based amorphous alloy is a kind of function material with good soft magnetic property, so it has extensive prospect of application. With the improving of stability under high temperature, more and more domestic and international researchers have been attracted to research on it.Firstly, chemical constituents of (Fe1-xCox)86Hf7B6Cu, alloys were designed in this article. Then, master alloy was obtained by vacuum arc furnace smelting equipment. Finally, (Fe1-xCox)86Hf7B6Cu1(x=0,0.05,0.1,0.3) of amorphous alloy ribbons were prepared by melt spinning of single roll casting method. The obtained thin tape alloy have the thickness in 30μm-40μm, width in about 3 mm. The samples were analyzed by X-ray diffraction (XRD), and the results indicate that (Fe1-xCox)86Hf7B6Cu1(x=0 and x=0.1) have occurred obvious crystallization, but (Fe1-xCox)86Hf7B6Cu1(x=0.05 and x=0.3) have one amorphous packet respectively which are complete amorphous. The transmission electrical microscopy analysis indicate that the diffraction rings of (Fe1-xCox)86Hf7B6Cu1(x=0.05 and x=0.3) are disperse cyclic structure, and the pattern of the matrix is homogeneous, so the determination results of the as-quenched samples are in amorphous state. Mossbauer spectrum analysis of two samples indicate the as-quenched alloy presents a typical broadened and overlapped sextet, and the second and fifth peaks are higher than the first and the sixth peaks obviously, which confirmed amorphous state.The amorphous thin ribbons were treated by low-frequency magnetic pulsing. The parameters of pulsed magnetic field are pulse frequency from 10 Hz to 40 Hz, pulse time from 90s to 300s and field between 150Oe and 350Oe respectively. Using the Mossbauer spectrum (MS), vibrating sample magnetometer (VSM), transmission electron microscope (TEM), differential thermal analysis (DTA), microhardness tester and so on, microscopic structure, the thermal stability, magnetic and mechanical properties of the amorphous thin ribbons after magnetic pulsing were studied.The thermal analysis shows that samples of Fe82Co4Hf7B6Cu, and Fe60Co26Hf7B6Cu, have two exothermic peaks in the DTA curve respectively. Both correspondences with the crystallization peaks of amorphous alloy, and with the increasing of the heating rates, the exothermic peaks all shift to the direction of high temperature. Through calculation, we find that the crystalline activation energy of sample Fe60Co26Hf7B6Cu1 is 1.59 ev lower than 2.25 ev of sample Fe82Co4Hf7B6Cu1, that is to say the amorphous thin ribbon which contain high Co crystallizing easily.The low frequency magnetic pulse treating can lead to the microcrystallization of amorphous alloys at room temperature. With the increasing of the pulse frequency, the field or the treatment time, the amount of the crystallization is increasing. Preliminary research on the soft magnetic property of Fe82Co4Hf7B6Cu1 and Fe60Co26Hf7B6Cu1 indicate that the saturation intensity of Fe82Co4Hf7B6Cu1 treated in different pulse strength is weaker than as-quenched. The coercive force and the saturation intensity are not monotonously changing with the increasing of the magnetic pulsing frequency. The soft magnetic property is optimum when H=222Oe, T=240s, f=20Hz.