Study On Sm-Co Nanocomposite Permanent Magnets

Recently, Sm(Co, M)7 phase exhibits excellent high temperature magnetic properties such as high Curie temperature (Tc=850℃), high anisotropy field(HA=10～18 T) and low coefficient of coercivity (β=-0.11%), etc, so rare-earth permanent magnet composed of main phase of Sm(Co, M)7 has a better potential application prospect as high-temperature permanent magnet. According to nanocomposite theories, nanocomposite magnetic matrial consisted of Sm(Co, M)7 andα-Fe could possess excellent comprehensive magnetic properties through exchange coupling effect between magnetically hard phase and soft phase. Moreover, such composite magnet with relative low rare-earth content and low price is hopeful to use as new generation practical permanent magnet.In this paper, Sm(Co, M)₇/α-Fe(M=Cu, Fe ,Zr ,B) nanocomposite permanent magnetic material with high performance has been prepared by crystallizing as-spun ribbons. X-ray diffractometer, Scanning Electronic Microscope, Transmission Electronic Microscope, Vibrating Sample Magnetometer and Thermogravimetric Analysis/Differential Scanning Calorimeters are empolyed to analyze the influence of melt-spun speed, crystallization process parameters, and cotent of B or Fe on microstructure and magnetic properties of Sm(Co, M)₇/α-Fe(M=Cu, Fe ,Zr ,B) melt-spun ribbons. The results show that the addition of Fe or B and melt-spun speed have little influence on phase compositions of as-spun ribbons, namely, all melt-spun ribbons mainly consisit of Sm(Co, M)7 andα-Fe. And crystallization process makes Sm(Co, M)7 phases decompose into 2:17R, 1:5 andα-Fe. There exist varying degrees of exchange coupling effects between magnetically hard phases and soft phases in melt-spun ribbons.Furthermore, as-spun Sm₁₂Co₆₀Cu₆Fe₁₉Zr₃ ribbons melt-spun at different speed mainly consist of non-preferred orientation equiaxed crystal area, preferred orientation columnar crystal area and dentritic crystal area. Sm₁₂Co₆₀Cu₆Fe₁₉Zr₃ ribbons as-spun at optimum speed of 20 m/s, have the best comprehensive magnetic properties with Hci=1301.9 Oe, Mr=39.27 emu/g, Mr/Ms=0.52 and the value of I(002)/I(111) achieves 3.81. Increasing addition of Fe will increase theα-Fe content in as-spun and as-annealed Sm₁₂Co_60-xCu₆Fe_19+xZr₃ (x=1-10) ribbons, and will simultaneously change coercivity mechanism of the as-annealed ribbons. In addition, Sm₁₂Co₅₇Cu₆Fe₂₂Zr₃ ribbons annealed at 900℃for 10min have the best comprehensive magnetic properties with Hci=2131.4 Oe,Mr=30.06 emu/g and Mr/Ms=0.43. With increasing addition of B, amorphous forming ability of Sm₁₂Co_60-xCu6Fe₁₉Zr₃Bx(x=0-5) alloys will improve, and the stability of Sm(Co, M)7 phases will become bad. Sm₁₂Co₅₅Cu₆Fe₁₉Zr₃B₅ ribbons melt-spun at speed of 20 m/s are almost composed of amorphous. But when annealed at 600℃for 10min, the ribbons have the best Mr=75.34 emu/g and Ms=118.97 emu/g.