Preparation Of FeSiBPCu Amorphous Nanocrystals And Study Of Their Crystallization And Soft Magnetic Properties

Fe-based amorphous/nanocrystalline alloys have broad application prospects in power systems and energy fields due to their excellent soft magnetic properties,simple preparation process and low raw material cost.However,in the commercialized Fe-based amorphous/nanocrystalline alloy system,the saturation magnetic induction intensity is still much lower than that of silicon steel(about 2.0 T).The amorphous forming ability of the alloy system with high Fe content is weak and its application scope is limited by the lack of strip thickness and width.In this paper,the single-roll quenching method was used to prepare the Fe-Si-B-P-Cu amorphous/nanocrystalline alloy thin strip,and XRD,SEM,TEM,DSC,VSM,electrochemical workstation and other characterization methods were used to conduct phase structure analysis,surface morphology analysis,thermodynamic parameter test,hysteresis loop test,corrosion resistance test,etc.The influence of composition change on amorphous formation ability,saturation magnetization,thermodynamic stability and corrosion resistance was studied.The effects of temperature and time on the crystallization precipitates and saturation magnetization intensity of alloy ribbons were analyzed.The non-isothermal crystallization kinetics of Fe₈₀Si₆B₁₀P₃Cu₁ amorphous thin strips under five heating rates of5,10,20,30 and 40 K/min were analyzed.The main results are as follows:(1)Using the method of element substitution,element B is added to the Fe_94-xSi₂B_xP₃Cu₁(x=6,8,10,12,14 at.%)alloy thin strip,and the alloy crystallization peak gradually decreases with the increase of the addition of B.Fe₈₀Si₂B₁₄P₃Cu₁ and Fe₈₂Si₂B₁₂P₃Cu₁ show complete amorphous structure,which indicates that the addition of B is beneficial to improve the amorphous formation ability of the alloy.The corrosion resistance of the alloy with higher B content is better.With the addition of B content,the saturation magnetization of the alloy is basically unchanged.?-Fe precipitates in all the annealed strips.(2)The Fe₈₀Si_2+XB_14-XP₃Cu₁(x=0,1,2,3,4)amorphous alloy thin strip was successfully prepared.With the replacement of Si element,the initial crystallization temperature T_x1 of the alloy moved to the lower temperature zone,the temperature range between the initial crystallization and the secondary crystallization increased,and the saturation magnetization decreased slightly.The isothermal crystallization annealing of Fe₈₀Si₆B₁₀P₃Cu₁ alloy was carried out at different temperatures and different times.The maximum saturation magnetization of Fe₈₀Si₆B₁₀P₃Cu₁ alloy was 179 emu/g when the temperature was 730 K and the maximum saturation magnetization was 10min when the temperature was 700K?810 K.At the annealing temperature of 730 K,when the holding time increases from 20min to 60 min,the optimum saturation magnetization is 189emu/g at the holding time of 60min.(3)The calculation results of non-isothermal crystallization of Fe₈₀Si₆B₁₀P₃Cu₁amorphous alloy show that the difference of global activation energy of crystallization obtained by the two methods is only about 5 k J/mol.The local crystallization activation energy calculated by FWO method increases first and then decreases with the crystal fraction.The change of Avrami exponent n during the crystallization process was calculated by JMA equation.The nucleation rate of the first crystallization decreased with the increase of temperature,which was mainly the diffusion controlled three-dimensional growth.The nucleation rate of the second crystallization also decreases with the increase of temperature,but the rate of decrease is faster than that of the second crystallization,and the growth mode is changed from interfacial control to diffusion control.