| Fe78Si9B13 metallic glasses have vast application prospects in transformer and sensors production due to their excellent soft magnetic properties,good glass-forming ability and low cost.Before using it,workers will utilize field annealing to optimize magnetic properties and introduce magnetic anisotropy.However,the magnetic anisotropy in metallic glasses still remains a puzzle,and needs further investigations.Thus,we want to study the magnetic anisotropy and the structure in Fe-based amorphous alloy.We chose the Fe7sSi9B,3 alloys as studying object,and set the heredity phenomenon as entry point.We researched the magnetic and structural anisotropy in amorphous materials and explained the origin of anisotropy.And we further found the structural relationships between crystalline ingots and amorphous ribbons.In the second part,we treated the amorphous ribbons with directional pressure annealing.Then,we investigated how the crystallization behavior,magnetic property and crystallization behavior changed with different directional treatments.And finally,the orders’ role in determining properties of amorphous alloys have been discussed.By using X-Ray Diffraction(XRD),Transmission Electron Microscope(TEM),Scanning Electron Microscope(SEM)and Electron Backscattered Diffraction(EBSD),we found that in the ingot samples,both the<100>α-Fe and<001>Fe2B axes are aligned parallel with the radial direction(RD)of the original cylindrical ingot,i.e.the maximum temperature gradient direction,and their other orthogonal axes have several preferred directions in the plane vertical to RD.Thus,the hard axis of the ingot is parallel to RD,which is due to the large magnetocrystalline anisotropy energy difference between<001>and {001} of Fe2B phase.This was verified by Vibrating Sample Magnetometer(VSM).For the amorphous ribbons,there is an in-plane magnetic anisotropy:the easy or hard axis of magnetization is aligned on the plane of the ribbon,and parallel to or at an angle of about 60° to its width direction,respectively.Magnetic domain’s structure was investigated by Magneto-Optic Kerr Effect(MOKE),the surface part was closure domain and the bulk part was stripe domain.By implementing Ferromagnetic Resonance(FMR),Fe-Si and Fe-B clusters were found.These clusters have in-plane magnetic anisotropy and the angles between easy axis and hard axis of Fe-Si and Fe-B are same with their crystalline counterparts.Based on structural heredity between the melts and glasses/crystals during solidification,we deduce that the magnetic anisotropy in the ribbon plane can be ascribed to the orientation alignment of Fe-Si and Fe-B clusters,i.e.a hidden order beyond short-range order,in Fe78Si9B13 amorphous ribbons.Under the Ar atmosphere,the amorphous ribbons were treated by directional pressure(along with axial direction and width direction)by using hot pressing furnace.Then,the treated samples were characterized by Differential Scanning Calorimetry(DSC),XRD,VSM.We found that annealing made the sample precipitate a-Fe,while the pressure annealing hindered the crystallization,and made the magnetic property better than the annealed sample.The mechanism is that the pressure minimize free volume,and decrease the diffusion ability.Especially,when the pressure was along with width direction,the crystallized degree was smaller than other samples.This is due to the fact that the pressure along width forms more clusters which have different structures with crystalline phase,and decrease more free volume.There were two crystallization reaction when implemented DSC measurements.All the samples have similar crystallization mechanism,they start with the JMA model,and then follow the NGG model.For the first crystallization,growth activation energy(Egrowfth)of pressure annealing sample is larger,this is because it’s a diffusion controlled growth.The decrease of diffusion ability caused by pressure has an obvious effect on it.However,for second crystallization,there is no difference of Egrowth between different samples when crystallization volume fraction is larger than 0.1.This is because it’s a interface controlled growth.The decrease of diffusion ability caused by pressure has no effect on it. |
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