The Fecunbsib, And Fesib Of Amorphous / Nanocrystalline Soft Magnetic Powder Cores Preparation And Performance Study

Metal soft magnetic powder cores are widely used in inductance component and low power transformers, and amorphous/nanocrystalline based soft magnetic powers can replace traditional Fe-Ni, MPP and sendust power cores because of its excellent soft magnetic properties. In this paper, the crystallization kinetics of Fe_78.4Cu_0.6Nb_2.5Si_9.5B₉ and Fe₇₃Si₃B₂₄ amorphous have been studied. Meanwhile, the influence of preparation procedure of powder and powder cores on the effective permeability, quility factor, DC superposition characteristic, coercivity,core loss and compressive strength have been investigated. The results are as following:(1) Compared with Fe₇₃Si₃B₂₄ amorphous, the Fe_78.4Cu_0.6Nb_2.5Si_9.5B₉ amorphous is much easier to obtain the microstructure of amorphous mixed with nanocrystllline due to the addition of Cu and Nb, which leads to the increase of the gap between the apparent activation energy of the second crystalline stage and that of the first crystalline stage.(2) Excellent soft magnetic properties can be obtained by subsequent annealing the Fe_78.4Cu_0.6Nb_2.5Si_9.5B₉ and Fe₇₃Si₃B₂₄ amorphous in 540℃and 520℃for 40 minutes,respectively.(3) Soft magnetic powders with mixed amorphous and nanocrytalline can be obtained by subsequent annealed ribbon ball milling, atomization and ball milling the atomization powders.With the decrease of atomization powder size, the amount of amorphous increase and grain size declines. During the process of ball milling atomization powders, with the elongation of ball milling time, the interplanar space, amount of amorphous and crytal strain of the powders increase and the grain size declines. After ball milled for 120 hours, the amount of amorphous of Fe_78.4Cu_0.6Nb_2.5Si_9.5B₉ and Fe₇₃Si₃B₂₄ powders close to 98% and 78%, respectively. With the elongation of ball milling time, the saturation magnetic induction of the powders is almost unchanged and the coercivity of the powders increase.(4) Powder cores produced by different process have the constant permeability between the frequency of 1KHz and 1000KHz.The soft magnetic properties and compressive strength are influenced by powder preparation procedure, powder size, kind of coating agent as well as its amount, compacting pressure and the stress relief annealing temperature. Power cores with high permeability and high compressive strength can be obtained by using large size ball milled ribbon Fe_78.4Cu_0.6Nb_2.5Si_9.5B₉ powders and power cores with excllent DC superposition characteristic, low coercivity and low core loss can be obtained by using small size ball atomization Fe_78.4Cu_0.6Nb_2.5Si_9.5B₉ powders. Organic coating agent is more helpful than inorganic coating agent in increasing the soft magnetic properties of powder cores. The decrease of permeability and rise of coercivity accompanied with the increase of coating agent. With the increase of coating agent, the DC superposition characteristic gets better and the core loss decrease firstly then increase. The powder cores made by 2wt.% organic coated ball milled ribbon powers have high strength, density, permeability and low core loss as well as low coercivity. The strength and soft magnetic properties can be significantly improved by increase the compact pressure. The soft magnetic properties of powder cores can be greatly improve by stress free annealing. The powder cores with high permeability, low coercivity and low core loss can be obtained by annealing the power core in 500℃for 1 hour.(5) By compacting 2wt.% organic coated ball milled Fe_78.4Cu_0.6Nb_2.5Si_9.5B₉ ribbon powders under the pressure of 1.6GPa, and then annealed the power core in 500℃for 1 hour, powder cores with high compressive strength, high permeability,excellent DC superposition characteristic,low coercivity and low core loss can be obtained.