Effect Of Mn/Cr Microalloying On The Amorphous Forming Ability And Soft Magnetic Properties Of Fe-based Amorphous Alloys

Fe-based amorphous strip has excellent soft magnetic properties due to its unique structure.The amorphous stator can increase the efficiency of the motor by 3-15%,reduce the iron loss by 85-90%,and the market scale can reach hundreds of billions of yuan.However,the magnetic properties of amorphous alloys with high Fe content(above 80 at.%)are greatly affected by changes in the local structure,and the local structure changes are complicated by the doping of metalloid elements and metal element microalloying.Therefore,the formulation of amorphous alloy with high saturated magnetic induction(Bs)and the control of melt purity need to be solved urgently.In this paper,the effects of Mn and Cr microalloying on the amorphous formation ability and magnetism were studied XRD(Mo-target)experiment and Mossbauer measurements are used to study the influence of local atomic structure changes on Bs by distribution function and coordination number analysis,and the structure-activity relationship of composition,structure and property was established;A new type of high-Bs Fe-based amorphous alloy is designed,and the element content is controlled by appropriate purifying agent ratio,melting temperature,melting time,etc.,to provide theoretical support for the industrialization of high-Bs Fe-based amorphous alloyFirstly,the influence of Mn,a common impurity element in industrial production,on the amorphous forming ability and soft magnetic properties of Fe80Si9-xB11Mnx(x=0.1-0.5,1 at.%)system was studied.The experimental results show that the addition of a small amount of Mn(0.3 at.%)can enhance the AFA of the amorphous alloy,and improve the thermal stability and the Curie temperature(Tc)of the amorphous alloy.At the same time,when 0.2 at.%or 0.3 at.%Mn is added,the amorphous alloy exhibits higher Bs and lower coercivity(Hc),and has better soft magnetic properties.By studying the average hyperfine field obtained by the Mossbauer measurements and the change of the lattice parameter of ?-Fe in the annealled ribbons,the improvement of Bs by Mn doping is explained from the variation of the microstructure parameters.And by analyzing the cluster size and atomic coordination,the relationship between structure and performance is established,which provides guidance for controlling the impurity element Mn in the industrial production of Fe-based amorphous alloysSecondly,the effect of Cr element on the properties of Fe-Si-B amorphous alloys with different Fe content was studied.The study found that in the Fe80Si9-xB11Crx system,0.4 at.%Cr improves the thermodynamic stability and Tc of the alloy system,and the crystallization mode changes,which corresponds to the best result of the amorphous forming ability;in terms of soft magnetic properties,with the trace doping of Cr,0.3 at.%and 0.4 at.%Cr make the amorphous alloy show good soft magnetic properties:lower Hc and higher Bs.In the Fe82Si7-xB11Crx system,when 0.4-0.6 at.%Cr is doped,the sample has better amorphous forming ability,which is a completely amorphous amorphous structure;at the same time,the addition of 0.5 at.%Cr increases the Tc of the alloy system,and also increases the Bs of the alloy to 1.627 T.Based on the study of Mn/Cr microalloying with different Fe content,a change rule of local clusters with the addition of trace elements is summarized,and according to the theoretical coordination number CN formula,a calculation model of the trace element addition amount to achieve the best Bs is proposed,and the structure-activity relationship between composition,structure and property was established,which provide a reference for microalloying to improve the soft magnetic properties of Fe-based amorphous alloysThirdly,the preparation of Fe-based amorphous alloys with high Fe content and high Bs is achieved by Mn/Cr microalloying.The optimal Mn/Cr doping amount of Fe84Si6B10 system with high Fe content was calculated by using the theoretical coordination number,and the differences of the amorphous forming ability and soft magnetic properties of three different doping(Fe84Si5.4B10Mn0.6,Fe84Si5.3B10Cr0.7 and Fe84Si5.4B10Mn0.3Cr0.3)were compared and studied,this article uses the difference in electronegativity to explain the strength of the three amorphous formation capabilities:Fe84Si5.3B10Cr0.7,Fe84Si5.4B10Mn0.3Cr0.3>Fe84Si6B10,Fe84Si5.4B10Mn0.6.At the same time,the addition of a single Mn or Cr does not significantly improve of Bs,which is related to the aggregation of a single antiferromagnetic element Mn or Cr,while the Bs of Fe84Si5.4B10Mn0.3Cr0.3 amorphous alloy increases to 1.65 T,which provides a new idea for the improvement of the soft magnetic properties of Fe-based amorphous alloy with high Fe content.Finally,the slag removal behavior and the change of Mn content of the ternary purification agent B2O3:CaO:MgO=3:0.8:0.2 on the Fe84B8Si4P3C1 master alloy under different purification times were studied.After 30 minutes of purification,the surface of the alloy ingot is bright,and the slag removal performance is good;at the same time,the curve of Mn content change with time during the purification process is fitted,which provides guidance for the control of impurity Mn during the industrial purification process significance.After the purification reaction stabilizes,the amorphous forming ability of Fe84B8Si4P3C-alloy is improved,the coercivity Hc is reduced to 5.48 A/m,Bs is increased to 1.654 T,and the comprehensive soft magnetic properties of the amorphous alloy Fe84B8Si4P3C1 are improved.