Study On The Fabrication And Magnetic Properties Of Fe-based Amorphous And Nanocrystalline Alloys

Fe-based metallic glasses have been widely used in industrial fields such as iron core and transformer due to their excellent mechanical properties and magnetic properties.It also has important theoretical research value and potential engineering application background.In present article,a series of(Fe,Co)-Nb-B,Fe-Co-(Mo,Ni)-Nb-B and Fe-Nb-B-Cu multi-component Fe-based metallic glasses were successfully fabricated by melt-spinning method.By the combination use of X-ray diffraction(XRD),differential scanning calorimeter(DSC),vibrating sample magnetometer(VSM)and four probe resistivity tester,the thermodynamic properties,magnetic properties and resistivity of these metallic glasses were investigated in detail.The(Fe1-x Cox)67Nb6B27(x=0-0.5)metallic glasses were prepared using the substitution of Fe by Co element,and the influence of Co element on glass forming ability(GFA),soft magnetic properties and resistivity was studied.The effects of transition elements,i.e.,Mo and Ni,on the GFA and soft magnetic properties of(Fe0.5Co0.5)68-x Nb6B26 Mox and(Fe0.5Co0.5)64Nb6-x B30 Nix metallic glasses were also studied.In addition,Fe81-x Nb5B14Cux(x=0,0.25,0.5,0.75,1;at%)and Fe83-x Nb3.5B13.5Cux(x=0,0.5,1,1.5;at%)alloy were prepared.The mechanisms of the replacement of Fe by Cu on GFA,soft magnetic properties and resistivity were explored.The Fe Nb BCu nanocrystalline alloys were also prepared by isothermal crystallization process.The relationship between the crystallization mechanism and the soft magnetic properties was studied.The main conclusions are as follows:The Co element plays an important role on the GFA in the(Fe1-x Cox)67Nb6B27 metallic glasses.With the increase of Co content,the GFA of the alloy was significantly improved.The alloys with x=0.5 exhibit the best glass forming former with ?Tx=140 K,Tx=956 K,andTrg=0.568.The replacement Fe element by appropriate Co element was beneficial to increase their saturation magnetization.However,excessive addition of Co element would deteriorate their magnetic properties.It was mainly ascribed to the exchange coupling between Co element and Fe element which changes the average atomic magnetic moment.The alloys with x=0.15 reach the maximum saturation magnetization of 112 emu/g.The addition of Co element significantly increased the electrical resistivity of the alloy.The resistivity reaches the maximum value of 230 ?? cm for alloys with x=0.5.The(Fe1-x Cox)67Nb6B27 metallic glasses exhibit a correspondence between thermal stability and electrical resistivity.Partial replacement of Fe by Mo element enhances the GFA of(Fe0.5Co0.5)68-x Nb6B26 Mox metallic glasses,and(Fe0.5Co0.5)66Nb6B26Mo2 alloys exhibit the best glass forming ability,with?Tx=104 K and Trg=0.605.However,Mo addition deteriorates their soft magnetic properties.The saturation magnetization reduces from 81 emu/g to 59 emu/g,while the coercive force does not increase significantly.The GFA of(Fe0.5Co0.5)64Nb6-x B30 Nix metallic glasses is directly related to the alloy composition.Minor Ni addition is found to enhance their GFA,while excessive Ni addition decreases their GFA.The(Fe0.5Co0.5)64Nb5B30Ni1 alloys exhibite the best glass former with ?Tx=115 K,Trg=0.604,and ?=0.413.The saturation magnetization and coercivity of the alloy is 65~86 emu/g and 0.02 ~ 0.06 Oe,respectively.The replacement of the Fe by Cu can improve both the GFA and the soft magnetic properties.The results show that the proper amount of Cu addition can effectively inhibit the precipitation of ?-Fe(200)crystallization phase,which enhances their GFA.However,excessive addition of Cu elements will promote the precipitation of ?-Fe(110)crystallization phase,thus deteriorating their GFA.In addition,the saturation magnetization of the alloy increases significantly.Higher Cu content results in better magnetic properties of the alloys.The saturation magnetization and coercivity of Fe81-x Nb5B14 Cux alloys are 104~115 emu/g and0.05~0.18 Oe,respectively.And the saturation magnetization and coercivity of Fe83-x Nb3.5B13.5Cux alloys are 76~114 emu/g and 0.10~0.22 Oe,respectively.Isothermal annealing results indicate that the crystallization process of Fe80Nb5B14Cu1 and Fe82Nb3.5B13.5Cu1 alloys is as follows: amorphous ? amorphous+?-Fe ? ?-Fe+Fe2B+Fe3B.During the crystallization process,the Cu element is found to refine the grain.The Cu clusters provide a large number of nucleation sites during the crystallization process,which aggravate the competition between these grains.A large number of nanoscale ferromagnetic ?-Fe grains is fomed,thus improving their magnetic properties.The Fe82Nb3.5B13.5Cu1 nanocrystalline alloys are excellent soft magnetic materials with high saturation magnetization of 171 emu·g-1and low coercivity of 0.19 Oe.