Study Of Formation And Electromagnetic Properties Of Bulk Amorphous Alloy Cofebsinb Series

Multi-component CoFeBSiNb bulk amorphous alloys in a cylindrical form with adiameter of 2ram were prepared by means of copper-mold vacuum suction casting. Theglass forming ability (GFA), the thermal stability, the soft magnetic properties and themagneto-impedance effect of these alloys were investigated by differential scanningcalorimeter (DSC), X-ray diffraction (XRD), vibrating sample magnetometer (VSM)and IM6 chemic station. The main results obtained are summarized as follows:(Co_xFe_1-x)₇₂B_19.2Si_4.8Nb₄(x=0.50,0.55,0.60,0.70,0.7443)bulk amorphousalloys in a cylindrical form with a diameter of 2ram were prepared by means of coppermold vacuum suction casting. As the content of cobalt element increases, the GFA of[(Co_xFe_1-x)_0.75B_0.20 Si_0.05]₉₆Nb₄ alloy will decrease. When the ratio of cobalt to iron(Co/Fe) increases from 5:5 to 7:3, theΔT_x drops from 65℃to 18℃, and someamount of crystal phase will appear in the alloy with a diameter of 2mm. The glasstransition temperature (T_g), the onset temperature of crystallization (T_x), thesupercooled liquid region (ΔT_x) and the crystallization peak temperature(T_p) for(Co_0.5Fe_0.5)₇₂B_19.2Si_4.8Nb₄ bulk amorphous alloy are 562℃, 627℃, 65℃and 641℃,respectively.ΔT_x for x=0.55, x=0.60, x=0.70 and x=0.7443 is 42℃, 20℃and18℃, respectively.CoFeBSiNb type bulk amorphous alloys show excellent magnetic properties, i.e.,high magnetic permeability, very low coercive force. The saturation magnetization (Ms)of (Co_0.50Fe_0.50)₇₂B_19.2Si_4.8Nb₄ bulk amorphous alloys with a diameter of 2mm were133.2emu/g. When the ratio of Co/Fe increases from 5:5 to 6:4, the saturationmagnetization, Ms, drops from 133.2emu/g to 122.5emu/g. After annealing heattreatment at 510℃for 0.5hour,1.0 hour,1.5 hour and 2.0 hour, Ms was 109.8emu/g,103.1emu/g, 109.5emu/g and 116.4emu/g, respectively.Co-based amorphous alloys have low impedance. The value of impedanceincreases slightly firstly with the increase of the AC driving current frequency and afterfrequency is above 1.3MHz, it increases rapidly .then decreases. Their peak values appear at the same frequency value, 1.6MHz; after the same frequency value, the valueof impedance decreases sharply. The saturation H_ex to reach the maximum of magneto-impedance effect in the soft magnetic amorphous CoFeBSiNb type bulk amorphousalloys increases with the increase of the AC driving current frequency. After annealingheat treatment at 510℃for 1.0h, the increased maximum MI ratio are obtained in theannealed samples.