Synthesis And Magnetic Properties Of Fe-based Bulk Metallic Glasses

.Due to their excellent soft magnetic properties, iron-based bulk metallic glasses exhibit high saturation magnetization and low coercivity, which have a better application than traditional soft-magnetic materials. Usually, the rigorous fabrication of iron-based bulk metallic glasses,even traces of oxygen and other impurities would induce the heterogeneous nucleation and reduce the glass forming ability (GFA ) drastically. In this work, iron-based bulk metallic glasses with composition of [(Fe_0.5Co_0.5)_0.75Si_0.05B_0.2]₉₆Nb₄ and Fe₆₁Co₆Zr₈Mo₇B₁₅Al₁Y₂ were synthesized successfully with copper mould casting by using the raw materials which were in low purity.In order to enhance the glass forming ability and the magnetic properties of the Fe₆₁Co₆Zr₈Mo₇B₁₅Al₁Y₂ alloy, a part of Zr in the base system is replaced by the element of Hf. The results shown that the Fe61Co6Zr5Hf3Mo7B15Al1Y2 alloy exhibits the largest GFA and has an extremely high Tg of 928 K, which is the highest value of any Fe-based BMG systems reported to date. The wide supercooled liquid regionΔTx and a high Tg demonstrates a high thermal stability of the present Fe-based BMGs. Besides, the substitution of Hf for Zr also enhances the magnetic properties, as verified by the increase in saturation magnetization (Ms) in the alloy of Fe61Co6Zr3Hf5Mo7B15Al1Y2, whose Ms is 37.8 emu/g and can be approximately 1.5 times higher than that of the base alloy (x=0) at room temperature. To be noted that Ms for the present BMG alloys were still relatively low although the addition of an appropriate amount of Hf increase scientifically the saturated magnetization. This is inherently due to the relatively low ferromagnetic concentration (67 at. %) on the base of analysis.The previous work has shown that the minor addition or suitable substitution of element is an effective way to improve the GFA and tailor the properties of Fe-based amorphous alloys. In this dissertation, the Fe61Co6Zr3Hf5Mo7B15Al1Y2 system is chosen for further investigation. Bulk metallic glasses (BMGs) Fe64Co6Hf5Mo7B15Y3 with the diameter of 3 mm have been produced by copper mold casting technique using industrial raw materials (such as Fe-B alloy). In addition, the Fe64Co6Hf5Mo7B15Y3 alloy has an excellent soft magnetic properties with the high saturation magnetization (50.5 emu/g) and the low coercivity (only two or three Oe). It is found that the substitution of an appropriate amount of Co for Fe can extend the glass formation range of the Fe64Co6Hf5Mo7B15Y3 base alloy,as demonstrated by successfully synthesizing a series of new Fe-based bulk metallic glasses. Otherwise, the present system has an excellent soft magnetic properties, which shows in saturation magnetization (45-66 emu/g) and in low coercivity. Furthermore, they can be broaden the magnetic application of the Fe-based BMGs, such as core storage and sensor.