Research On The Magnetic Properties And Preparation Of Fe-B-P Amorphous Alloy

Fe-based amorphous alloys have been widely attracted great interests of researchers due to unique properties in applications.Researchers are pursuing the excellent magnetic properties on the basis of continuous attempts to improve Fe concentration in the iron-based amorphous alloy.However,the ability of amorphous formation ability,coercivity and other properties deteriorate dramatically with increasing of the Fe concentration.In order to solve the above problems,research on the magnetic properties and preparation of Fe-B-P amorphous alloy were studied.The alloy composition was designed through Near-Free Electron Concentration Theory and the alloy strip was prepared by rapid solidification method.The composition of the alloy was measured by XRD,thermodynamic properties was determined by DSC,and magnetic properties was measured by VSM.The main content and conclusions in this thesis are divided into the following parts:Based on the Near-Free Electron Concentration,it is found that the e/a of(Fe3P0.18B0.82)25 and(Fe3P0.37B0.63)25 alloy samples is 1.59 and 1.68,respectively,which is closer to 1.6,the electron concentration when Fe-Si-B amorphous alloy has the best glass forming ability(GFA).It can be seen that the(Fe3P0.18B0.82)25 and(Fe3P0.37B0.63)25 alloys should have high GFA.The structure,thermal stability and magnetic properties of the alloy samples prepared at different cooling rates are analyzed.The results show that(Fe3P0.37B0.63)25 alloy has higher GFA than(Fe3P0.8B0.82)25,while the(Fe3P0.18B0.82)25 alloy has higher saturation magnetic.But the crystallization phase of Fe3P0.37B0.63 is unstable and easily converted into Fe3P0.18B0.82 crystallization phase and other phases during the process of solidification and precipitation.The influence of Nb substitution for Fe on the precipitation of a-Fe,GFA and magnetic properties of the(Fe85-xB10P5Nbx)(x=0,1,3,4,5at%)alloys are investigated.Based on the XRD measurement of the melt-spun ribbons,it is found that thedominant crystal plane in a-Fe precipitates gradually changes from(200)to(110)with increasing Nb content from 0 at%to 5 at%and then only broad peaks without any appreciable crystalline peaks can be observed when Nb content is 5at%.The same phenomenon of microstructural evolution also exists in the addition of other elements M(M=Ni,Mo,Y,Cr and Si)which can be well explained based on the Bravais-Friedel law and the negative mixing enthalpy between Nb(or M)and Fe(or B).Furthermore,the strong bonding between Nb and Fe atoms results in the formation of Fe-Nb clusters and then enhances short-range-order clusters,leading to the enhance of GFA and decrease of coercive force from 13.82 A/m to 2.3 A/m with the addition of Nb content less than 4 at%.With further increasing Nb content,the coercive force becomes higher,which is contributed to the formation of Nb-B clusters and the poor solute-solute avoidance.The composition design for Fe-based amorphous alloys with high Fe content is researched based on the Nearly-Free-Electron model,which indicates that there is a favorable electron concentration(e/a)value for amorphous formation.The Fe-B-P-Sn amorphous alloys with Fe content higher than 83%have been designed based on the favorable(e/a)value.The amorphous alloy samples were prepared and tested to study the effects of the addition of Sn content to Fe-B-P alloys on its amorphous forming ability and magnetic properties.The results demonstrates that the addition of Sn under the same Fe content contributes to the increase of saturation magnetic induction intension of the Fe-based amorphous alloy.Accurate control of the metal-like alloy with an electron concentration of about 1.6 will make the Fe-based amorphous alloy have high amorphous ability and lower coercivity.