Preparation And Magnetic Properties Of Fe-based Bulk Metallic Glasses

Iron-based bulk metallic glasses, which exhibit high saturation magnetization and low coercivity, are promising for the future application as a new kind of soft magnetic materials. In this work, iron-based bulk metallic glasses (BMGs) with composition of Fe72Y4Nb2B22 and (Fe71.2B24Y4.8)96Nb4 were synthesized successfully into glassy rods with diameters of 3.3mm and 4mm respectively, by using copper mould suck casting and low purity raw materials.In order to enhance the glass forming ability (GFA) and magnetic properties of the (Fe71.2B24Y4.8)96Nb4 alloy system, alloying strategy was used by partially replacing the Nb with Zr and Fe with Co respectively. As a result, the new (Fe71.2B24Y4.8)96Nb3Zr1 BMG with diameter of 5mm and [(Fe1-xCox)71.2B24Y4.8]96Nb4(x=0.1～0.4) BMGs with diameter of 3.3mm were prepared successfully by using industrial raw materials, which largely broaden the glass forming region(GFR). The detailed results shown that the GFA of the alloy system was greatly improved by the substitution of only 1at.% Zr for Nb, while deteriorated rapidly with increasing Zr content. On the other hand, the GFA of the alloy system was not affected obviously with the substitution of Co for Fe, suggesting a broad glass forming region. The thermal analysis shown that the two alloy systems had high glass transition temperature (Tg) and broad supercooled liquid region, indicating high thermal stability.In order to evaluate the improvement of magnetic properties by alloying effect, magnetic testing method was applied to systemically investigate the effect and mechanism on the magnetic properties of the (Fe71.2B24Y4.8)96Nb4 alloy system with Zr and Co substitution. Room temperature test shown that the saturation magnetization of the alloy system would be efficiently enhanced by the proper Co substitution and reached the maximum value of 98emu/g, which was 10% higher than that of the base alloy. Thermomagnetic test shown that the Curie temperature raised up successively with the increasing Co content and reached the maximum value of 575K, which was 100K higher compared with the base alloy. As a result, the thermomagnetic properties were greatly improved by the Co substitution, which would be promising for the better performance at high temperature. Besides, the effects of different critical cooling rates on the saturation magnetization (Ms) were measured. The discrepancy between the values of Ms was attributed to the ferromagnetic cluster and inhomogeneous structure formation during the glass forming.