Study On Preparation And Properties Of Fe-Nb-B-(Cu,Ni,Co) Multi-component Fe-based Amorphous Alloys

Fe-based metallic glasses have been widely used in electronic power fields due to their excellent mechanical properties and soft magnetic properties.Thus,it is of important theoretical and practical application value to prepare new type of Fe-based metallic glasses with both large glass forming ability?GFA?and excellent soft magnetic properties.In present thesis,a series of Fe-Nb-B-Cu and Fe-?Co,Ni?-Nb-B-Cu multi-component Fe-based metallic glasses were successfully fabricated by melt-spinning method.Structure characterization,thermal properties,magnetic properties and electrical resistivity of these alloys were investigated by X-ray diffraction?XRD?,differential scanning calorimetry?DSC?,vibrating sample magnetometer?VSM?and a four probe tester.The relationship between properties and composition in the Fe-based metallic glasses was explored.Additionally,the crystallization kinetics in the Fe_76.5Nb₃B₂₀Cu_0.5 metallic glasses was investigated,and the nucleation and growth mechanism was explored.The main conclusions can be drawn as follows:The Fe_67-xNb₅B₂₈Cu_x?x=0.0,0.5,1.0,2.0?metallic glasses exhibit high thermal stability with T_x1?913 K.However,their GFA increases firstly and then decreases with the increase of Cu content.The M_s and H_c of these alloys reaches 86⁹0 emu·g^-1 and 0.02⁰.86 Oe,respectively.As the Cu content increases,the electrical resistivity of the alloys increases firstly and then decreases.The Fe_66.5Nb₅B₂₈Cu_0.5 alloys exhibit the optimum GFA and electrical resistivity with?T_x=45 K,T_rg=0.585,and?=138??cm.Differential scanning calorimetry?DSC?was used to investigate the non-isothermal crystallization kinetics of the Fe_76.5Nb₃B₂₀Cu_0.5 metallic glasses.The activation energies of E_x and E_p calculated by Kissinger method are equal to 558±7 and 693±2 kJ mol^-1,respectively,and 543±9 and 680±2 kJ mol^-1 estimated by Ozawa method,respectively.The results indicate that the E_x values calculated by two methods are all smaller than that of E_p,suggesting that the nucleation process is easier than the grain growth process.The Avrami exponent n?x?varies with the crystallized volume fraction x,incidating that there are different crystallization mechanisms in the crystallization process.The n?x?ranging from 1.0 to 1.2 for 0.05<x<0.2represents the growth of particles of appreciable initial volume.The 0.5<n?x?<1.0 for x ranging from 0.2 to 0.8 stands for the growth of a large number of the pre-existing nuclei.The Fe_80-xNb₅B₁₄Cu₁Co_x?x=1,2,3,4?metallic glasses were prepared by partial substitution of Co for Fe,and the effects of Co element on thermal stability,GFA,soft magnetic properties and electrical resistivity were studied.Both thermal stability and GFA of these alloys increases firstly and then decreases with increasing Co content.The alloys with x=3exhibits the best GFA and high thermal stability with T_x1 and T_rg being of 747 K and 0.544,respectively.As Co content increase,their saturation magnetization?M_s?firstly increases and then decreases,and the M_s reaches the maximum value of 105 emu·g^-1 for alloys with x=2.The electrical resistivity of the alloys ranges from 128??cm to 150??cm,and it increases firstly and then decreases with the increase of Co content.By substituting Fe with Co and Ni,the Fe_80-x-yNb₅B₁₄Cu₁Co_xNi_y?x=2,y=2;x=2,y=3;x=3,y=2;x=3,y=2;x=3,y=3?metallic glasses were prepared.The effects of Co and Ni contents on thermal stability,GFA,soft magnetic properties and resistivity were investigated.The results show that both thermal stability and GFA increase with increasing Co and Ni.And the alloys with x=3 and y=3 exhibits high thermal stability and GFA with T_x1=754 K and T_rg=0.550.The saturation magnetization M_s and coercivity H_c in the Fe_80-x-y0-x-y Nb₅B₁₄Cu₁Co_xNi_y alloys are equal to 93¹01 emu·g^-11 and 0.04².37 Oe,respectively.Their electrical resistivity increases from121??cm to 163??cm.