Dissertation
Dissertation > Industrial Technology > General industrial technology > Materials science and engineering > Special structural materials

High-Temperature Magnetic Properties and Mechanism of Exchange-coupling Interaction for FeCo-based Nanocrystalline Alloys

Author YangJing
Tutor WangZhi
School Tianjin University
Course Condensed Matter Physics
Keywords Initial permeability Magnetostriction coefficient Penetration depth exchange coupling
CLC TB383.1
Type Master's thesis
Year 2010
Downloads 71
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This paper studies the Fe 78.4-x CoxSi 9 B 9 Nb 2.6 Cu 1 (x = 27.4, 40, 51, 78.4) series amorphous and nanocrystalline magnetic alloy microstructure and high temperature magnetic origin of the microscopic mechanism and explore the Ni and the addition of alloy magnetic energy. Focus on analysis of the microscopic mechanism of the Co content under magnetic alloy high temperature and room temperature and high temperature magnetic origin. XRD analysis of the alloy microstructure. Were studied at different times and different annealing temperature of 500 ℃ isothermal annealing of alloy microstructure and magnetic. Origin the software simulation XRD diffraction peak calculated crystalline phase volume fraction, grain size and the remaining thickness of the amorphous layer. The results indicate that the annealing conditions have a significant effect on the microstructure of the alloys, the annealing temperature and the annealing time variation of the thickness of the crystallized volume fraction of the alloy, the lattice constant, and the residual amorphous layer has a significant impact. With increasing annealing temperature, the annealing time of growth, the crystalline phase volume fraction increases, while decreasing the thickness of the amorphous layer between the grain, the lattice constant increases, but its value has been less than the lattice of the bcc-FeCo constant. Measure AC initial permeability μ i variation with temperature (ie the μ i -T curve) to study the high-temperature magnetic properties of the alloy. Using online measurement of the change of the initial permeability, to obtain the relationship between the magnetic permeability within the range of from 20 ° C to 800 ° C and the temperature. The results show that the Co partial substitute for the alloy of Fe can significantly improve the amorphous phase of the the FINEMET type alloy Curie point, the alloy μ i holding to a higher temperature is not decreased significantly, but the addition of Co but so that the decline in saturation magnetic induction, the magnetostriction coefficient increased, resulting in a significant decline in the magnetic permeability at room temperature. The nanocrystalline alloy by a different temperature vacuum annealing after the initial permeability with the variation of the temperature within the wide range in the amorphous phase above the Curie temperature and found that the initial magnetic permeability of the alloy after high temperature annealing is not significantly attenuated This is a new phenomenon, observed in the two-phase nanocrystalline alloy magnetic properties different from the Fe-based nanocrystalline alloys. We take advantage of the exchange coupling model Hernado Fe alloys using theoretical calculations and experimental validation of the method FeCo-based alloys at high temperatures the microscopic mechanism of exchange coupling, complete exchange coupling between the two-phase nanocrystalline alloy grain apparent Curie temperature of the penetrating action, between the grains of the amorphous layer can be a substantial increase to the same temperature as the Curie point and the crystalline phase (i.e. the T- C A = T C α ), and calculated α-FeCo grains completely the exchange coupling penetrate role in the critical thickness (Λ c ) less than α-Fe grains Λ c , explained FeCo-based nanocrystalline alloys permeability was significantly higher than that of Fe-based nanocrystalline alloys at high temperatures. In order to improve the FeCo nanocrystalline alloy of the initial magnetic permeability, in the nanocrystalline alloy, FeCo joined the different content of Ni, and tested the Ni content on the magnetostriction, Curie temperature, the saturation magnetic flux density and initial permeability rate and magnetic parameters. The results showed that, after the addition of Ni can significantly improve the initial permeability of FeCo-based nanocrystalline alloy, but reduced the Curie temperature of the alloy.

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