Research And Application Of Fe-based Amorphous And Nanocrystalline Alloys With High Saturation Magnetization

Under the environment of energy saving,environmental protection and sustainable development in modern world,soft magnetic materials are developing towards energy saving,integration and miniaturization,which require materials to have high saturated magnetization M_s,low permeability H_c,high permeability and high resistivity.As a new generation of soft magnetic materials,Fe-based amorphous and nanocrystalline alloys exhibit more excellent properties than traditional soft magnetic materials,which are due to the low average magnetic anisotropy caused by the interaction betweenα-Fe nanocrystalline phases and amorphous phases in the alloy.At present,Fe-Si-B-Nb-Cu nanocrystal alloy（FINEMET）has been applied industrially as a magnetic core material.However,its saturated magnetization is only1.24 T and is not suitable for the miniaturization of equipment.The saturated magnetization M_sof commercial Fe Si B 1K101 amorphous alloy is about 1.5～1.6 T,which is lower than that of traditional silicon steel.In recent years,M_sof Fe-Si-B-Cu,Fe-B-Cu and other nanocrystalline alloy systems developed have reached 1.75 T,but there is still great room for improvement in their coercivity,thermal stability,amorphous forming ability and other properties.Therefore,in this dissertation,We researched the effects of element addition,preparation process and annealing process on amorphous forming ability,as-quenched structure,thermal stability,crystallized structure,magnetic properties and resistivity of Fe-Si-B-P,Fe-Si-B-P-Cu,and Fe-Si-B-Cu-Ca amorphous nanocrystalline alloys.Finally,a new type of magnetic source was designed and fabricated with commercial 1K101 amorphous alloy ribbons,and the magnetic filed property was investigated.The conclusions are as follows:（1）The amorphous forming ability of Fe_85-xSi₃B₁₂P_x（x=0,1,2,3,4,5）was continuously improved with the addition of element P,and for x=4 and x=5,the alloys are of amorphous strcture.Coercivity H_cof the alloys showed a decreasing trend with the addition of P element,and for x=5,the as-quenched coercivity H_cwas only 3.46 A/m.With the increase of Fe content replaced by P,the saturated magnetization M_sdecreased continuously,from 1.71 T for x=0 to 1.58 T for x=5,and the value showed a decrease of7%.However,for x=4,the as-quenched saturated magnetization of the amorphous alloy is1.64 T,which is better than 1.56 T of the commercial 1K101 Fe Si B alloy.（2）Fe₈₅Si₂B_12-xP_xCu₁（x=0～4）had a coercivity of 54.53 to 122 A/m,which decreased with the increasing of P content.For the content of P was x=4,the coercivity was 54.53 A/m,which decreased by 54%compared with 118.7 A/m of the alloy content without P addition.In addition,the addition of P also made the supercooled liquid regionΔT_xincrease,from119℃at x=0 to 153℃at x=4,which increased by 28.6%.（3）Fe₈₄Si₂B₈P₅Cu₁and Fe_83.5Si_2.5B₈P₅Cu₁showed a coervitity H_cof 24.4 A/m and 18.35A/m after heat treatment at 440℃and 420℃,respectively,and the corresponding saturated magnetization M_swas 1.79 T and 1.67 T respectively.The soft magnetic properties of A/m,and M_s=1.86 T,H_c=22.71 A/m after heat treatment at 440℃.Compared with the Fe₈₄Si₂B₈P₅Cu₁alloy with the same Fe content,the soft magnetic property was better.（4）For Fe₈₄Si_xB_10.5-xP₅Cu_0.5（x = 0⁵.5）,we can get a completely amorphous state ribbon when Si content was x=5.5,and the supercooled liquid regionΔT_xwas 133℃,showing that the alloy have a good amorphous forming ability and thermal stability.After 10minutes of heat treatment at 440℃,the soft magnetic property was M_s=1.85 T and H_c=12.96 A/m.As the heat treatment temperature increased from 450℃to 480℃,the coercivity of Fe₈₄Si_5.5B₅P₅Cu_0.5alloy increased continuously,and the coercivity was 26.53 A/m when the temperature was 480℃.As the heat treatment time increased from 20 minutes to 60 minutes,coercivity increased from 18.17 A/m to 60.71 A/m.（5）the addition of a small amount of Ca element had an effect on the amorphous forming ability of(Fe₈₂Si₃B₁₄Cu₁)_100-xCa_xalloys.When the Ca content was x=0.18 and 0.24,the fully amorphous ribbons can be obtained in the as-quenched state.For x=0.18～0.48,the nanocrystalline alloys contained only a singleα-Fe phase after annealing.The resisitivity of resistivity was 137.6μΩ.cm and for x=0.48～0.72,the resistivity was higher than 228.8μΩ.cm.The resistivity after heat treatment was lower than as-quenched state.In addition,high Ca content can promote the formation of high resistivity Fe₃B nanocrystals phase in the alloy both before and after annealing.and the resisitivity of annealed(Fe₈₂Si₃B₁₄Cu₁)_100-xCa_xincreased with the addition of Ca,for x=0.72 the resistivity reaches 171.3μΩ.cm,much higher than 116.2μΩ.cm for x=0.（6）A new type of magnetic source was fabricated with commercial 1K101 amorphous alloy and DT4 pure iron.And when the current intensity was 5 A,a maximum of space magnetic induction intensity B could reach 173.5 m T in the protruding end of the iron bar,which was much higher than the biggest magnetic induction intensity of the flat end and coreless added magnetic source.The result showed that the protruding structure can significantly improve the ability to convergence magnetic force line.