The Effect Of Alloying And Magnetic Field Heat Treatment On High Frequency Magnetic Properties Of Fe-based Amorphous Nanocrystalline Ribbons

Soft magnetic materials are the key to efficient operation of power electronics and electrical machines.With further introduction of wide bandgap semiconductors in power electronics and motor control,there is an urgent need to improve the performance of soft magnetic materials,enabling them to operate at higher frequencies and meet power requirements,making the electronic devices more efficient,smaller and lighter.Iron-based amorphous/nanocrystalline alloys are widely used in power electronic devices because of their low magnetostriction coefficient and reduced random magnetic anisotropy to obtain excellent soft magnetic properties.Generally,the operating frequency region of iron-based amorphous/nanocrystalline alloys is in between 0.5 kHz and 150 kHz.However,as the operating frequency increases,the permeability decays more rapidly and cannot meet the design requirements of the device in a higher frequency.Therefore,the development of soft magnetic materials with excellent high-frequency magnetic properties has become a hot spot in the field of materials research.In order to improve the soft magnetic properties of Fe-Si-B-Cu-Nb type iron-based nanocrystalline soft magnetic alloys in their working frequency band,both alloying and magnetic field heat treatment approaches are taken measure in this paper.On the one hand,a series of silicon-rich Fe-Si-B-Cu-Nb-?P,Mo?amorphous alloy ribbons were prepared by single-roller quenching method.Then the effect of the addition of P and Mo on amorphous forming ability,crystallization and soft magnetic properties were investigated.The effect of the 1K107 series industrial ribbons?Fe-Si-B-Cu-Nb?were prepared by industrial single-roller quenching method,and the effect of magnetic field heat treatment on their high frequency soft magnetic properties were studied.?1?For Fe_73.5Si_15.5B_7-xCu₁Nb₃P_x?x=0,1,2,3,4,5,6?alloys,as x?3.0at.%,complete amorphous alloy ribbons can be attained.With the increase of P/B ratio,the onset primary crystallization temperature(T_x1)decreases,the onset secondary crystallization temperature(T_x2)also decreases,the interval of two onset crystallization temperatures??35?T_x?becomes smaller.For the Fe_73.5Si_15.5-xB₇Cu₁Nb₃P_x?x=0,1,2,3,4?alloys,all quenched alloys are a completely amorphous structure.With the increase of P/Si ratio,T_x1 of the amorphous alloy is slightly larger,and the T_x2 becomes smaller.For Fe_73.5-xSi_15.5B₇Cu₁Nb₃P_x?x=0,0.5,1,1.5,2?alloys,all samples also are completely amorphous structure.With the increase of P/Fe ratio,T_x1 keeps basically steady,T_x2 moves to the low temperature zone,and?35?T_x becomes narrow.?2?When Fe_73.5Si_15.5B₆Cu₁Nb₃P₁ amorphous alloy annealed at 480°C⁵60°C for 60 min,the coercivity is less than 1.8 A/m.When the annealing temperature was at 520°C,the effective magnetic permeability??_e?of the core in the 1-30 kHz is higher than that of alloy without phosphorus,?e is 120k at 1 kHz.For the Fe_73.5-xSi_15.5B₇Cu₁Nb₃P_x?x=0.5,1.0,1.5?amorphous alloys,when annealed at 520°C,the effective permeability of the cores is improved at 1 kHz,the x=1 at.%alloy is up to 87k.?3?For Fe_72.5Si₁₆B₇Cu₁Nb_3.5-xMo_x?x=0,1.5,2.0,2.5,3.0?alloys,as x=0 at.%?Mo0?and x=1.5 at.%?Mo1.5?,the alloys with a completely amorphous structure can be prepared.Then the sample begins to occur crystalline phases as the Mo content further increasing.The alloy without Mo element exhibits distinct and separated two-stage crystallization peaks corresponding to the precipitation of?-Fe?Si?and Fe-B compounds respectively.With the addition of Mo,the alloy exhibits a third crystallization peak,corresponding the formation of?Mo,Nb?₃Si compounds.?4?For Mo0 and Mo1.5 alloys,when annealed at 520°C for 60 min,the coercivity is 1.5A/m,3.3A/m,respectively,the saturation magnetizations is 142.5emu/g,152.3emu/g,respectively.When the frequency is higher than 20 kHz,the?_e of the Mo1.5 core is higher than that of Mo0 core,its?_e is 31k at 100 kHz.The addition of Mo has a positive effect on the high-frequency magnetic permeability.?5?A series of 1K107 industrial ribbons are a completely amorphous structure,and the magnetic domains are arranged irregularly and disorderly,like labyrinth.The T_x1 of all alloys is around 530°C,T_x2 is about 690°C,the?35?T_x of the 1K107B,1K107C and 1K107E alloy is162°C,158°C and 165°C,respectively.They all show relatively good thermal stability.?6?After ordinary annealing under N₂ flowing protection,the magnetic permeability of the iron-based nanocrystalline cores monotonously decreases with increasing of frequency,at first its reduction is rapid in the frequency range of 1 kHz to 40 kHz,then it becomes slow from 50 kHz to 200 kHz.The 1K107B core annealed at 550°C?60min show the optimum effective permeability,its?_e is 136k at 1kHz,and its?_e is 26k at 100kHz.When annealed at560°C for 60min,both 1K107C and 1K107E cores exhibit a high effective permeability at a range of low frequency??<20kHz?,its?_e is 162k and 143k at 1kHz,respectively.1K107C core annealed at 550°C?60min show high effective magnetic permeability at high frequency,the?_e is 27.9k at 100kHz.?7?When first annealed at 550°C for 60 min then annealed at 480°C for different holding time with transverse magnetic field,the effective magnetic permeability of the iron-based nanocrystalline core is depressed at the low frequency zone,while at the high frequency band gets improved to some degrees.Within 1 kHz to 200 kHz,the core quality factor?Q?is improved and the core loss is reduced.By comparison,the optimum holding time of transverse field annealing of 1K107B,1K107C,1K107E is 180min,240min,180min,respectively,the magnetic core can possess excellent comprehensive soft magnetic performance.?8?When first annealed at 550°C for 60 min then annealed at 360⁵20°C with transverse magnetic field for 180 min,with the increase of annealing temperature under transverse magnetic field,the effective magnetic permeability of the cores in the low frequency band gradually decrease overall,however,the effective magnetic permeability of the high frequency band rises,then a maximum point appears,and then falls again.For the 1K107B,1K107C and1K107E cores,the highest effective permeability at 100 kHz is obtained at 440°C,480°C and500°C,respectively,shows 37.7k,37.8k and 32.4k,respectively,increasing by 44%,35%,and26%compared to magnetic cores that were not transverse field annealing.For the quality factor Q of the magnetic cores,as the annealing temperature rises,the quality factor first rises and then decreases,however the total loss of the core decreases.After transverse field annealing,no new phase appears inside the alloy ribbons,and the size of nano?-Fe particle keeps almost constant.