Study On The Sm-Fe-Co-Al-B-Type Amorphous-based Permanent Magnetic Materials

In recent years, because of their excellent performance, amorphous materials have been widely used in functional materials areas. Hard magnetic alloys of Sm-Co series have excellent magnetic properties and play an irreplaceable role in high temperature area. In this article, we try to add Fe, Al, B to Sm-Co alloy to prepare amorphous based magnets and find a new way for a new type of permanents.The ribbons are prepared by arc-melting and melt-spinning technique in this article and tested by the means of x-ray diffractometer, scanning electron microscopy, vibrating sample magnetometer, high resolution transmission electron microscopy and other equipments. The influence of melt-spun speeds and content of Al on the phases compositions, microstructure and magnetic properties, the magnetic mechanism, and the effects of B on the formation of amorphous are studied.The results show that melt-spun ribbons of Sm10-25Fe8-15Co50-70Al5-20B2-10 series have the composite structure of amorphous/nanocrystalline generally. With the increase of melt-spun speed, the content of amorphous in the ribbons will rise, but the phase compositions don’t change, which includes SmFe2, SmCo2, Sm2Co7, Sm2Co7B3, AlFe and Co0.72Fe0.28. When the melt-spun speed is 40 m/s, the ribbons of Sm25Fe10Co50Al10B5 have the best magnetic properties, Hc = 8595.32 Oe, Mr = 10.91 emu/g, Ms = 14.82 emu/g,Mr/Ms = 0.74. The stability of amorphous in the ribbons will improve with the increasing of melt-spun speeds. The content of Al can affect the microstructures and magnetic properties of Sm15Fe10Co70-xAlxB5(x = 0, 5, 10, 15, 20) ribbons prominently. The main phase of the ribbons of this series alloys at a speed of 40 m/s is Sm(Co,M)7. With increasing the content of Al, the highest peak of Sm(Co,M)7 moves left, remenence and saturation magnetization of alloy will decrease gradually, while the coercivity increases at first and then decreases. When the content of Al is 15 at%, the ribbons will possess the highest coercivity(Hc = 14.65 kOe). With adding Al, some of Al atoms go into SmCo7 and replace some Co atoms, which enhances the anisotropy field, and then improve the coercivity. The other Al atoms form cell structure in the ribbons, amorphous and 1:7 phase are in the cell, and there are several crystalline in the wall of the cell. Through pinning the movement of domain wall and ronation of domain in cell-wall by the nonmagnetic phases and the exchange coupling between soft and hard magnetic phases, the materials have the good magnetic properties. Comparing Sm10Fe15Co60Al10B5 and Sm10Fe15Co60Al5B10, we can find that the GFA will be improved substantially, and the Sm10Fe15Co60Al5B10 ribbons with more B have the better magnetic properties. The radius of B is very small, it can enter the interval of crystal lattice, which increases the density of atom close packing and the difficulty of atom movement, then improve the GFA.