双相纳米复合永磁材料Nd8.2-xPrxDy0.8Fe85Nb1B5(x=1，2，4，7，8.2)磁性能和微结构的实验研究

　　双相纳米复合永磁材料Nd8.2-xPrxDy0.8Fe85Nb1B5(x=1，2，4，7，8.2)磁性能和微结构的实验研究
　　The permanent magnet can carry out the mutual convert of electromagnetic energy to mechanical energy or sound energy through the interaction of magnetic poles and the magnetic field in the interspace. Thus permanent magnetic materials have extensively applications in many realms of production and life. Nanocomposite permanent magnetic material is a new type of rare-earth magnet, which composes of soft phase and hard phase with nanoscaled microstructure, is founded on the basis of exchange-coupling theory. Nanocomposite permanent magnetic material possesses both the high remanence of the soft phase and the high coercivity of the hard phase and is expected to be a new generation of permanent magnetic material with excellent properties. In this work, we prepared nanocomposite Nd8.2-xPrxDy0.8Fe85Nb1B5(x = 1, 2, 4, 7, 8.2) ribbons using the melt-spinning technique with different wheel speeds and heat treatment conditions. The phase components of the samples Special shape NdFeB magnets were analyzed with X-ray Diffraction (XRD). Transmission Electron Microscopic (TEM) was used to observe the microstructures of the samples and to evaluate their grain sizes. The magnetic properties of the ribbons were measured by Vibrating Sample Magnetometer (VSM). The main results of this work are as follows:1. For Nd8.2-xPrxDy0.8Fe85Nb1B5(x = 1, 2, 4, 7, 8.2) ribbons melt-spun with a speed of 45 m/s, the annealing temperature/timeincreases with the increase of Pr content.
　　The optimum magnetic properties of (BH)m = 104.86 kJ/m3, HCI = 540.4 kA/m, Mt = 787.13 kA/m, Mt/Ms = 0.75 were obtained in Ndg^-xPrxDyo.sFegsNbiBs (x = 4) sample under the optimum annealing condition 580°C/3min. The magnetic properties of nanocomposite Ndg^-jcPrxDyo.sFegsNbiBsCx = 1, 2, 4, 7, 8.2) ribbons are affected mainly by two factors, i.e., the content of Pr and the mean grain size of the soft and hard phases. When the mean grain size of the sample fits the critical size of exchange coupling interaction, the magnetic properties of the samples are obviously enhanced by small amount of Pr substitution for Nd.2. The best magnetic properties of (BH)m = 121.5 kJ/m3, Hcx = 391.7 kA/mr MT = 1511 kA/m, Mr/Ms = 0.65 were obtained in Nd4 2Pr4Dyo gFegsNbiBs ribbons prepared by controlled-melt-spinning with a http://www.999magnet.com wheel speed of 15 m/s + subsequent annealing technique. These magnetic properties are much better than that of the other samples prepared by "high speed melt-spinning (v > 30 m/s) +subsequent annealing " and " direct crystallization" (v<10 m/s)" techniques. The main reason is that the ribbon prepared by the controiled-melt-spinning with a wheel speed of 15 m/s +subsequent annealing technique has finer mean grain size, which is the essential factor for the better magnetic properties.3. The Nd^.2Pr4Dyo.8Feg5NbiB5 ribbons prepared by the controlled-melt-spinning with a wheel speed of 20 m/s and 25 m/s have their preferred orientation. The easy axes of the samples arein the plane of the ribbons. The nucleation and growth of grains during the quenching process are mainly influenced by two factors: One is the temperature gradient of the sample, which results in the easy axis of the sample perpendicular to the plane of the ribbon. Another is the inducement effect of oc-Fe {110} crystallographic texture, which results in the easy axis of the sample in the plane of the ribbon. In our samples, the latter may plays the dominant role. This is the possible reason that the Nd4.2Pr4Dyo.8Feg5NbiB5 ribbons prepared by the controlled-melt-spinning with a wheel speed of 20 m/s or 25 ni/s have their preferred orientation.