Investigation On Structure Evolution And Soft Magnetic Properties Of FeNi-based Amorphous And Nanocrystalline Soft Magnetic Alloy

As one of the novel soft magnetic materials,FeNi based amorphous alloy has tremendous advantages,such as low coercivity(H_c),high permeability(?)and good frequency characteristics.It has been widely used in magnetic head,precision transformer,magnetic shielding and biosensor fields.However,FeNi-based alloys still have problems such as weak amorphous forming ability,low thermal stability,and low saturation magnetization.Therefore,devoting to the development of novel high-performance FeNi-based amorphous soft magnetic alloys will become one of the urgent tasks to ensure the development of power electronic equipment technology in the direction of high efficiency,lightweight and energy saving.In this paper,the driving force,thermodynamic stability,nanocrystalline structure soft magnetic properties and other related issues are revealed through the control of alloy composition design,the crystallization kinetics mechanism under isothermal and non-isothermal conditions is clarified,and the manufacturing process of high toughness amorphous alloys ribbon is grasped,so as to develop FeNi-based amorphous nanocrystalline soft magnetic alloys with high amorphous forming ability and excellent soft magnetic properties The main research contents of this paper are summarized as follows:(1)The effect of variation Nb content in(Fe₄₀Ni₄₀B₁₉Cu₁)_100-xNb_x(x=1,3,5,7)alloy ribbons on the glass-forming ability,thermal stability and soft magnetic properties of the alloy are investigated.The results show that with the increase of Nb content,the crystallization temperature range in the alloy is significantly improved,and at the same time,the apparent activation energy is also significantly increased,which effectively improves the thermal stability.When the Nb content is 3 at.%,the coercive force is the lowest 2 A/m,and the saturation magnetization M_s=103.7 Am²/kg,which has relatively good comprehensive soft magnetic properties.(2)The analysis of isothermal crystallization kinetics shows that when the Nb content is 3at.%,the crystallization behavior of the alloy is divided into three stages,the nucleation process of(Fe,Ni)₂₃B₆phase,the growth of(Fe,Ni)₂₃B₆phase and the nucleation and growth process of the?(Fe,Ni)phase,the entire crystallization process is transformed from a one-dimensional interface-controlled growth process to a three-dimensional interface-controlled growth process,and the nucleation activation energy and the growth activation energy are respectively E_n=429.2 k J/mol,E_g=417.2 k J/mol.(3)The effects of Si/B ratio on the glass-forming ability,thermal stability and soft magnetic properties of(Fe₄₀Ni₄₀Si_xB_yCu₁)_0.97Nb_0.03(Si/B=3:1,2:1,1:1,1:2,and 1:3)alloy were investigated.The results show that the glass forming ability of Fe-Ni-Si-B-Cu-Nb alloy system can be effectively improved by reasonably adjusting Si/B ratio,the T_rgcan reach 0.509,and the alloy has good thermal stability.When Si/B ratio is 1:1 and 1:2,the coercivity H_cis 0.3 A/m and 0.25 A/m respectively.At the same time,the isothermal and non-isothermal DSC analysis shows that the alloy with different Si/B ratio has different crystallization behavior.Si element can effectively inhibit the excessive growth of?(Fe,Ni)Si grains.(4)Based on the previous'work,the effect of P replacing B on the alloy was systematically studied.The results show that the low-costing P element can not only improve the glass-forming ability of the alloy,but also enhance the competition of precipitates during crystallization.In terms of soft magnetic properties,the coercivity of all alloys is basically?1 A/m,the maximum permeability is 17100,and the pinning field H_pis about 25-30 A/m.We found that P can effectively increase the precipitation density of?-Fe(Si)phase,and then improve the saturation magnetization M_sof the alloy.When P content is 3at.%,the M_sof the alloy reaches 97.6 Am²/kg.(5)Based on the adjustment of magnetic elements,the effects of different Fe/Ni ratios on the glass-forming ability,crystallization kinetics and soft magnetic properties of the(Fe_xNi_80-xSi_9.5B_9.5Cu₁)_0.97Nb_0.03(x=36,38,40,42,44)alloys were systematically studied.The results show that with the increase of Fe/Ni ratio,the reduced glass transition temperature T_rgof the alloy increases from 0.507 to 0.527,and the GFA of the alloy is obviously improved.Through kinetic analysis,it is found that?(Fe,Ni)Si is less dependent on the heating rate than?-Fe(Si)and(Fe,Ni)B,and the activation energy required for the formation of?(Fe,Ni)Si phase is much higher than that of?-Fe(Si)and(Fe,Ni)B phase.In terms of soft magnetic properties,the minimum coercivity of alloy x=36,38,40,42 and 44 are 0.14 A/m,0.11 A/m,0.23 A/m,0.08 A/m and 0.03A/m,respectively.Meanwhile,the maximum permeability is17000146001080012700 and 16500 respectively.