| With a view of developing new nanocrystalline Rare-Earth permanent magnets and improving the properties of existing nanocrystalline Rare-Earth permanent magnets, formation, structural and magnetic properties of metastable SmCo7 phase and Pr2Fe14B/α-Fe nanocomposite magnet have been investigated, using melt-spun technology. Furthermore, the coercivity mechanism of such permanent magnets is studied also.1.In the series of Sm-Co alloys, SmCo5 and Sm2Co17 exhibit excellent permanent magnetic properties and have been used as commercial products already. Another phase with almost the same intrinsic magnetic properties as that of SmCo5 and Sm2Co17, namely, SmCo7, has not been investigated adequately, due to the difficulty in the formation of SmCo7 structure. It is found that SmCo7 phase can be stabilized by substituting small amount of third element such as Zr, Ti or Cu for Co atom. Zr is the most effective stabilizing element and Cu is the least effective one. The ratio of Sm To Co that tends to form the SmCo7 structure is 1:7. In addition, melt-spinning is found to be the most effective technique to fabricate SmCo7 phase. It can decrease the amount of stabilizing element, enlarge the scale of Sm:Co and increase the amount of Fe substituted for Co without changing the SmCo7 structure. Even with a very high cooling rate, the magnetic properties of SmCo7 ribbons are very poor due to the poor amorphous formation ability. According to the theory of amorphous, the larger the difference in the size of constituent atoms, the easier the amorphous formed. So, small C atom is introduced into the SmCo7 alloys in an attempt to increase the amorphous formation abilities and consequently the coercivity. It is found that addition of C atom helps to reduce the grain size and improve the homogeneity of microstructure. Therefore, the hard magnetic properties are improved significantly. The maximum of coercivity and energy product are 14.3 and 10.9 , respectively. The saturation magnetization of SmCo7 alloys are decreased due to the addition of non-magnetic atom of Zr. It is well-known that the saturation magnetization of Sm-Co compounds can be increased by partially substituting Fe for Co. So the proportion of Fe is increased. As expected, the substitution of Fe for Co leads to an increase of saturation and remanent magnetization. But the coercivity falls off due to the fast decrease of anisotropy field. The maximum product of 13.7 is obtained for the proportion of Fe is 25%. According to the initial magnetization curve, magnetizing field dependence of reduced remanence and coercivity and Henkel Plot, the coercivity mechanism is controlled by inhomogeneous domain pinning. 2.Nanocomposite permanent magnets (NPMs) is newly emerged permanent magnets which is considered to bo the forth generation magnets that can replaces the sintered NdFeB magnets. But the properties are poor because of small coercivity. One reason is that the grain sizes are not small enough. Nanocrystalline Fe–Zr–Cu–B is an excellent magnetically soft material in which fine a-Fe grains embedded in a surrounding ferromagnetic amorphous matrix are formed. The refinement of microstructure results from the combined addition of Zr, Cu and B. Therefore, the composition of Pr9Fe82Zr2Cu0:5B6:5 with combined addition of Zr, Cu and B is designed in an attempt to obtain a fine microstructure and consequently an enhanced coercivity.Due to the combined addition of Zr, Cu and B, mean grain sizes of soft and hard magnetic phase decreased from16 and 28 nm for the ternary nanocomposite to 12 and 20nm. The rectangularity is improved and the coercivity is increased to 9.2. Due to the addition of nonmagnetic elements Zr, Cu and B, Mr and energy product are deduced. Another meaning of this result is the confirmation that decrease of grain size is a effective method to increase coercivity. The optimum melt-spun speed are reduced from 19-20 to 12.5 also. According to the initial magnetization curve, magnetizing field dependence of reduced remanence and...
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