FeSiB非晶软磁复合材料的制备及性能研究

Fabrication and Magnetic Properties of FeSiB-based Soft Magnetic Composites

将FeSiB非晶带材通过粉末冶金的方法制备成软磁复合材料。研究了钝化剂溶剂、质量分数及退火温度对材料形貌及性能的影响。采用乙醇作为磷酸钝化液的溶剂,并与水及丙酮溶剂对比。结果表明,水为溶剂时磁粉易被氧化;丙酮沸点低挥发快导致磷酸与磁粉反应不充分;乙醇为溶剂时能够形成均匀致密的磷酸盐包覆层,有利于降低复合材料的损耗。对于采用乙醇作为溶剂时磷酸质量分数(0.2%~0.8%)影响的研究表明,当磷酸质量分数为0.6%时,可获得最低损耗187 mW/cm^3(50 kHz,50 mT)。去应力退火温度低于400℃时,复合材料内应力不能充分释放,导致磁导率低且损耗高。退火温度高于425℃时,在保温过程中α-Fe相析出产生晶化。Fe Si B软磁复合材料在400℃/1 h退火后可获得最佳磁性能。

FeSiB soft magnetic composites （SMCs） were prepared via powder metallurgy with FeSiB ribbons as starting material. Influences of passivator solvent, content of the passivator as well as annealing temperature on the morphology and properties of the samples were investigated. Alcohol was used to dissolve phosphoric acid as the surface passivator and its effect was compared with that of water and acetone. Results show that the magnetic powders are prone to oxidation with water, while acetone hinders the complete surface passivation as a result of limited reaction time caused by low boiling point and strong volatility of the acetone. A uniform insulating coating can be achieved using alcohol as the passivator solvent and it decreases core loss of the composites. With the content of orthophosphoric acid varying between 0.2-0.8 wt% in alcohol, lowest core loss （187 mW/cm^3 measured at 50 kHz, 50 mT） can be obtained with 0.6 wt% of orthophosphoric acid. Stress relaxation is insufficient when the annealing temperature is below 400 ℃ for the SMCs, resulting in low permeability and high core loss, while precipitation and crystallization of the a-Fe phase occur with annealing temperatures higher than 425 ℃. Optimum properties of the FeSiB SMCs can be achieved by annealing at 400 ℃ for 1 h.