Preparation And Properties Modulation Of High B_s FeSiB(P,C)Cu Amorphous And Nanocrystalline Soft-magnetic Alloys

Fe-based amorphous and nanocrystalline alloys exhibit excellent properties such as low coercivity?H_c?,high permeability??_e?and low loss?P_c?.Which known as the energy saving and environmental protection functional device materials in the 21st century,and mainly used in transformer,servo motor,sensor and other technical fields.However,compared with the B_s of traditional silicon steel?1.9-2.1 T?,the B_s of the soft magnetic alloy is relatively lower?1.4-1.6 T?.In the context of global attention to environmental protection,the power electronic devices are in the development trend of miniaturization.Therefore,it has become an urgent problem to improve the B_s of the alloys.As the increase of B_s in the Fe-based amorphous nanocrystalline soft magnetic alloy need increaseing the Fe content,and reducing the content of amorphous forming elements and large atom-size elements,the amorphous forming ability of amorphous nanocrystalline soft magnetic alloy with high Fe content becomes poor,and the heat treatment performance is difficult to control.Neverthless,how to obtain high Fe content soft magnetic alloy with both high B_s and low H_c is a difficult problem.This paper researched the Fe-Si-B-?P,C?-Cu soft magnetic alloys,and modulated their soft magnetic properties by normal annealing,magnetic field annealing and rapid annealing.The nanocrystalline soft magnetic alloy with B_s as high as 1.79-1.87 T and H_c as low as 7.9-14.7 A/m were successfully obtained.Finally,the correlation mechanism between soft magnetic properties and microstructure was established.Summarised as follows:1.Via magnetic field annealing to modulat the soft magnetic properties of high Fe content?90-95.5 wt.%?Fe-Si-B-P-C amorphous alloys.Compared with normal annealing,magnetic field annealing can reduce H_c by more than 20%.Magnetic properties of high B_s of 1.62-1.66 T,low H_c of 0.8-2.6 A/m,high?_e of 11×10³ and low P_c of 0.052 W/kg?B_m=0.9 T and f=50 Hz?were obtained.Magnetic domain also investigated in detail,it is shown that magnetic domain structure of the amorphous alloys is closely related to the soft magnetic properties.For as-quenched alloys with good thermal stability,the branched magnetic domain structure can be obtained.After magnetic field annealing,stripe and well-distribution domain obtained.For the alloy with poor thermal stability,due to a large number of clusters contain in the as-quenched alloys,resulting in the large H_c,as well as disordered magnetic domains.After annealing,the magnetic domains are more uniform,but the size very small.This is the reason for the annealed alloys with growth of the?-Fe clusters.2.Cu was added to Fe-Si-B-P-C alloys as the nucleation of grains,to prepare high B_s nanocrystalline soft magnetic alloy.The results show that P and C could improve the amorphous forming ability?AFA?and soft magnetic properties,while soft magnetic properties will deteriorated if absence of P and C.In this paper,we successfully prepared nanocrystalline soft magnetic alloy with high B_s of 1.77-1.84 T,low H_c of 5.6-18.5A/m and high?_e of 1×10⁴.For the alloy ribbons with surface crystallized,?_e can be improve after the alloy ribbns polished 1?m.Severe oxidated of alloys deteriorated the soft magnetic properties,this is due to the transformation of Fe²⁺into Fe³⁺,i.e.,the transition from Fe₃O₄ to Fe₂O₃.3.The addition of Cu will reduce the AFA of Fe-Si-B-P-C alloys.Therefore,Cu-free nanocrystalline Fe-Si-B-P-C-Ni alloys with large?T_x,high AFA and without traditional large atomic elements were obtained.This soft magnetic alloy has extremely high B_s of 1.79-1.87 T,low H_c of 7.9-14.7 A/m and high?_e of 10000.Crystallization mechanism show that a large number of Fe atomic clusters occured in the alloys,and a small grain size of?-Fe?Si?could be obtained by rapid annealing.For the Cu-free alloys,the changes of Fe and Si elements are consistent,B and P elements be excluded from the amorphous matrix and enriched around the grains,and C elements will cover the?-Fe?Si?grains,forming a kind of spherical shell structure.The crystallization kinetics of Cu free nanocrystalline alloys shows that the large difference between nucleation activation energy and growth activation energy is the key to preparation the high performance soft magnetic alloys.