Study On The Addition Of Si,Fe,Cu And Nb On Microstructure And Magnetic Properties Of Multelement Sm₁₂Co_60-70M_28-18 Ribbon Magnets

Sm-Co-based magnets have been widely concerned for their excellent hard magnetic properties at high temperature. Amorphous Co-based alloys behave superior soft magnetic properties. The dual-phase nanocomposite materials could possess excellent comprehensive magnetic properties through exchange coupling effect between magnetic hard phase and soft phase. On the base of these theories, in this paper, the hard magnetic properties of amorphous nanocrystalline composite materials are expected to be improved by means of the exchang coupling interaction between the amorphous phase and nanocrystalline phase, which could be a new derection to explore new hard magnetic alloys.The amorphous and nanocrystalline composite alloys are prepared by arc-melting and melt-spinning method. The influence of melt-spinning speeds, crystallization process, and content of Si, Nb, Cu or Fe on microstructure and magnetic properties of melt-spun ribbons are studied by means of X-ray diffractometer, transmission electron microscope, scanning electro microscope and vibrating sample magnetometer etc.The results show that the content of Si directly influenced the microstructure and magnetic properties of the ribbons with a norminal composition of(Sm₁₂Co₆₀Fe₈Zr₅Nb₅Al₆B₄)100-xSix（x=0, 3, 6, 8） fabricated by melt-spinning with a wheel speed of 40m/s. With increasing x value, glass-forming ability（GFA） of the ribbons is improved, while the hard magnetic properties display a marked drop trend. The ribbons without Si addition have the best comprehensive magnetic properties of Hci=14.0kOe, Mr=13.5emu/g and Mr/Ms=0.88. The microstructure of the ribbons is composed of a typical nanocrystalline/amorphous matrix phases, and the size of nanocrystalline phases is less than 10 nm, in which all of clusters with much less than 10 nm were dispersed in the amorphous matrix. The demagnetization curves of the ribbons behave like that of a single hard magnetic phase. When the ribbons subsequently annealed at 750°C for 120 min, the coercivity of the ribbons with x=0, 3 and 6 improved obviously, and their average values were Hci=18.4k Oe, 15.6kOe and 18.1kOe respectively, while the ribbons with x=8 behaved the best comprehensive magnetic properties compared with corresponding unannealed ribbons when the annealing time is 20 min. Different melt-spinning speeds directly influenced the microstructure and magnetic properties of the ribbons with x=8. The ribbons with x=8 fabricated by melt-spinning at 10m/s have the comprehensive magnetic properties of Hci=9.6kOe, Mr=11.4emu/g and Mr/Ms=0.825. In addition, with Nb addition, the forming of the new tiny crystal phase for the ribbons with a norminal composition of Sm₁₂Co₇₀Fe₄Zr₆B₈Nbx（x=0, 2, 4） fabricated by melt-spinning with a wheel speed of 40m/s improved, while the comprehensive properties tend to be worse. The addition of Fe or Cu influences the phase compositions and microstructures of ribbons of Sm12Co60Fe10-xZr5Nb5CuxB8（x=2, 4, 6） fabricated by melt-spinning at 40m/s. When Fe addition decreases and Cu addition increases, the comprehensive magnetic properties of ribbons improved. The ribbons with x=6 have the best comprehensive magnetic properties of Hci=17.8kOe, Mr=28.9emu/g and Mr/Ms=0.906.