Preparation And Properties Of Co-based Amorphous Alloy

In recent years, a series of ferromagnetic amorphous alloys with largesupercooled liquid region and good soft magnetic properties have beenfound. Co-based amorphous alloy, not only has the characteristic of highmagnetic permeability, low coercivity, high standard of electricalresistivity and close to zero on magnetostriction coefficient, and also hashuge value of research and a wide financial foreground because of itsexcellent properties of hardness and wearability. As to this research, theglass forming ability (GFA), thermal stability, microhardness and softmagnetic properties have been investigated by means of X-ray diffraction(XRD), scanning electron microscope (SEM), differential scanningcalorimetory (DSC), microhardness and B-H loop analysis, etc. Also, byresearching the characteristic of glass forming ability (GFA),thermostability, mechanics and magnetics of as-quenched glassy ribbons.We are going to provide some certain proof for discovering and preparingCo-based amorphous alloy. Finally, we get the following conclusions:1) Co₄₅Fe_25-xZr_xNb₁₀B₂₀(X=0,2,3,4,5,6)glassy ribbons have been preparedby single roller melt-spinnig technique. The effect of wheel speed onthe glass forming ability have been reviewed. The higher the wheelspeed is, means the higher cooling rate is, the easier the glassy alloyforms.2) The effect of Zr on microstructure, GFA and thermostability ofCo-Fe-Zr-Nb-B alloy has been studied. As-quenched glassy ribboncontaining 4 at.% Zr shows the most homogeneous microstructure,the best GFA and the highest thermal stability. And it has beendiscussed by the mechanism of melt microstructure competing.3) Addition of Y can improve GFA and thermostability ofCo-Fe-Zr-Nb-B alloy greatly. There are two main reasons, on onehand, The reaction between yttrium and oxygen is thermodynamicallyfavored compared to the reaction between oxygen and the otherelements in the system. Therefore, the stability of the remainingliquid could be enhanced by the alleviation of the harmful effect ofoxygen, and the GFA of Co-based alloys can be improved; on the other hand large atomic size difference could enhance the packingdensity of the undercooled liquid, increase viscosity of alloy, restrainatomic diffusivity, thereby retard crystal nucleus formation andgrowth.4) Thermal stability of(Co₄₅Fe₂₁Zr₄Nb₁₀B₂₀)₉₆Y₄ was examined by DSCat various heating rates of 10, 20, 30 and 40K/min with Kissinger andOzawa equations as follows: The values of crystallization activationenergyΔE_x1 andΔE_p1 are 988 kJ/mol, 955 kJ/mol, respectively.5) Analyzed the microhardness of glassy ribbon under different state andwhich prepared at different wheel speed. The microhardness reduceswith the increasing of the wheel speed. It can be explained accordingto the free volume and the defect concentration model.6) Compacting the powder by grinding the glassy ribbon undercrystallization temperature. Glassy ring has been got with largesupercooled liquid region and good soft magneric properties.