Investigation On The Addition Of P Or Mo To Fe₇₆Si_13B8Nb₂Cu₁ Alloy With High Bs

With the development tendency of electronic components towards miniaturization,high frequency and energy saving,Fe-based nanocrystalline alloys require excellent high frequency characteristics under the condition of higher B_s.On the other hand,it is necessary to explore the industrial application of Fe-based nanocrystalline materials soft magnetic materials prepared by industrial raw materia.In this paper,select the high B_s Fe₇₆Si₁₃B₈Nb₂Cu₁ nanocrystalline alloy prepared with high purity raw materials as research object,explores the effect of preparation with industrial raw materials on the magnetic properties of this alloy.In order to improve the high frequency performance,the addition high purity P or Mo to Fe₇₆Si₁₃B₈Nb₂Cu₁nanocrystalline alloy is carried out and the high frequency characteristics of the alloy are studied.Finally,the evolution of the microstructure of the alloy added high purity Mo with the annealing temperature is studied.The main conclusions are summarized as follows:Firstly,the effects of preparation with industrial raw materials and industrial process on thermal properties,amorphous formation ability（AFA）,process and magnetic properties of Fe₇₆Si₁₃B₈Nb₂Cu₁ nanocrystalline alloys were studied.It was found that the Fe₇₆Si₁₃B₈Nb₂Cu₁ribbons with high surface quality and ductility were successful prepared with IRMs.The surface crystallization stimulated by impurity has negligible effect on crystallization behavior determined with DSC,but has a negative effect on annealing process windows.Relatively good magnetic properties attractive for applications were obtained,including low H_c of 3.5 A/m,highμ_e of28.8×10³ at 1 kHz,high B_s over 1.39 T,P_1T,1kHzT,1kHz of 0.91 W/kg and P_0.5T,10kHzof 5.3 W/kg.Compared with Finemet alloy（B_s=1.24 T）,B_s has a significant improvement.Secondly,in order to optimize the soft magnetic properties,especially improve the high frequency performance,the addition of high purity P or Mo element was carried out in the laboratory,and the AFA and thermal properties of the alloy were also studied.It was found that the addition of P or Mo does not reduce the AFA of the alloy,which still has a wide heat treatment temperature range.At the same time,alloy addition with high purity P or Mo element has better soft magnetic properties,including Bs>1.38 T,H_c from 1.9 A/m reduced to 0.6-0.7 A/m,100 kHz under the high frequency magnetic conductivity increased from 0.9x10⁴ to 1.5x10⁴..Finally,from the view of microstructure evolution,this paper explains the reasons why high B_s FeSiBNbCu alloy with addition of high purity P or Mo element has excellent soft magnetic properties and high frequency characteristics.It is found that the quenching sample contain completely amorphous structure,and exist irregular domain,the soft magnetic performance is poor.Once the annealing temperature（T_A）comes up to the beginning of crystallization temperature,theα-Fe grain began to precipitate,and the number ofα-Fe grain increase with the T_A increase.When T_A=580 ^oC,the small and evenlyα-Fe grain（about 12-13 nm）uniform distribute on amorphous matrix,and a wide and straight 180°stripe domain appears,which corresponding to better soft magnetic properties.As T_A continues to increase,hard magnetic phase appears and serving as a pinning site for magnetic domain,which would deteriorate magnetic properties.The study of the dynamic magnetization process of this alloy shows that the change of magnetic conductivity with applied field could be explained from the change of magnetic domain with the field.