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Preparation and structure of rapid quenching 1:7 SmCo permanent magnet materials and magnetic energy

Author: ZhangGuangTeng
Tutor: YiJianHong
School: Central South University
Course: Materials Science
Keywords: Melt-spun SmCo7 carbonide Ti coercivity
CLC: TM273
Type: Master's thesis
Year: 2009
Downloads: 25
Quote: 0
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Abstract


SmCo7 phase with TbCu7 structure is a non-equilibrium phase intervenient SmCo5 and Sm2Co17 phases. It has an excellent application prospect since it combines large magnetocrystalline anisotropy, high magnetic saturation and high Curie temperature. SmCo7 is a metastable phase, so it decomposes to SmCo5 and Sm2Co17 at high temperature. It used to be fabricated by melt-spinning and dope with Ti, Zr, B, Hf etc for phase stability. This dissertation mainly investigated the effects of carbonides on magnetic properties and structures of SmCo7-type permanent magnetic material. SmCo7-type material with grain size of nanometer scale and relative high coercivity had been attained through suitable design of alloy compositions and processing parameter. Phase structure and microstructure had been investigated using transmission electron microscopy (TEM), scaning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD).Research results demonstrated that WC, Cr3C2, VC were helpful in grain size refining of SmCo7 ribbons, and the refining effect of Cr3C2 is better than the others. TEM analysis showed that the main phase of (Sm0.12Co0.88)93(Cr3C2)7 ribbon (melt-spun at 20m/s) is～80nm of grain size, and a non-magnetic precipitated phase with a grain size of about 20nm containing C, Cr, Co had also been investigated. This non-magnetic phase and precipitated Sm2Co7 phase played a key role in domain wall pinning, which induced coercivity improving. (Sm0.12Co0.88)93(Cr3C2)7 ribbon melt-spun at 40m/s was amorphous, and it demonstrated good magnetic properties with iHc=635.4kA/m, Br=0.58T after annealing at 650℃for 6min. Annealing of (Sm0.12Co0.87Cu0.01)97(VC)3 had demonstrated that the coercivity increased largely while grain size changing is little. The reason of coercivity improving is that the intergranular phase transition inducing intensifying of domain wall pinning.The effect of Ti on structure and magnetic properties of SmCo7 ribbon had been study. SmCo6.7Ti0.3(Cr3C2)0.1 and SmCo6.7Ti0.3(Cr3C2)0.15 ribbons formatted uniformed structure even though in high melt-spun speed. SmCo6.7Ti0.3(Cr3C2)0.1 ribbon attained a high coercivity of 1993kA/m, while the SmCo6.7Ti0.3(Cr3C2)0.15 melt-spun at 50m/s demonstrated fine comprehensive properties with iHc=1153 kA/m, Mr=0.46T. SmCo6.7Ti0.3(Cr3C2)0.1 and SmCo6.7Ti0.3(Cr3C2)0.15 ribbons both precipitated a SmCo2 phase which is paramagnetism at room temperature. The strong domain wall pinning of SmCo2 is the reason of coercivity improving.

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CLC: > Industrial Technology > Electrotechnical > Electrical materials > Magnetic materials,ferrite > Permanent magnet materials, permanent magnet
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