Microstructure And Soft Magnetic Properties Of Rare Earth-modified Iron-based Nanocrystalline Materials

Iron-based nanocrystalline alloys have excellent soft magnetic properties such as high initial permeability,low coercivity and low core loss,as well as environmental friendly and low cost,which are widely used in common mode inductors,switching power supplies,motor stator/rotor materials,and other devices.Finemet alloy is a typical representative of iron-based nanocrystalline alloys,although it has excellent soft magnetic properties,it also has disadvantages of low saturation magnetic induction intensity and low magnetic permeability under high temperature and high frequency.In order to expand the application field of iron-based nanocrystalline alloys and reduce production costs,it is great significance for element substitution modification.In this paper,the effects of rare earth elements on the microstructure and soft magnetic properties of Fe-based nanocrystalline alloys were studied by adding rare earth Y/Gd elements to partially replace Nb or Fe in the alloys,and some devices were applied in practical applications.The specific research results are as follows:（1）Partially replace Nb with Y,when Y≤0.5%,the as-cast alloys were amorphous,and when Y≥1.0%,a crystalline phase appears in the as-cast alloys.When Y partially replaced Fe,the as-cast alloys were amorphous if Y≤1.5%.With the increase of Y content,the crystallization peak of the alloy moves to the high temperature region.Y can assist Nb to further refine the grains size.（2）Fe_73.5Cu₁Nb_2.5Si_13.5B₉Y_0.5 alloy with excellent comprehensive soft magnetic properties was developed.Theμm value reaches 813.1k,which is 36.45%higher than that of Finemet,and the Hc value is 0.56A/m;at 1k Hz,with the ambient temperature was 30～150°C,theμe value only reduced by 8.8%;at 150°C,theμe value reaches128.02k,which is 15.74%higher than that of Finemet.（3）Fe₇₃Cu₁Nb₃Si_13.5B₉Y_0.5 alloy with excellent comprehensive soft magnetic properties was developed.Theμi andμm values are 149.93k and 925.63k,which are22.19%and 9.67%higher than that of Finemet,respectively.At ambient temperature of 120°C and 150°C,at 1k Hz,theμe values are 156.86k and 145.71k,which are42.21%and 40.95%higher than that of Finemet.（4）Fe₇₃Cu₁Nb₃Si_13.5B₉Gd_0.5 alloy with excellent comprehensive soft magnetic properties was developed.The soft magnetic properties are as follows:theμi value is148.43k,and the Hc value is 0.36A/m.At 1k Hz and ambient temperature of 90°C and150°C,theμe values are 162.34k and 142.42k,which are 24.71%and 29.52%higher than Finemet,respectively.（5）After constant tension annealing,the dynamic soft magnetic properties of Fe_72.5Cu₁Nb₃Si_13.5B₉Gd₁ alloy were further improved.In the frequency range of1k Hz-1MHz,theμe value is 20～30%higher than that of Finemet.Moreover,theμe value of the alloy can be kept stable in a wider frequency range and has better frequency stability,so that it can be applied to fields with various magnetic permeability requirements,and has broad market application.（6）The preliminary application of several typical alloys shows:in the PC power filter,Fe_73.5Cu₁Nb_2.5Si_13.5B₉Y_0.5 alloy can realize single-stage filtering instead of two-stage filtering,which meets the requirements of device miniaturization;Fe₇₃Cu₁Nb₃Si_13.5B₉Y_0.5 alloy has excellent high temperature stability,which can meet the requirements of vehicle air conditioning filter system;the Fe_72.5Cu₁Nb₃Si_13.5B₉Gd₁ alloy can be applied in the smart meter measurement system,which can improve the metering accuracy.