Preparation And Characteristic Magnetic Properties Of Fe-based Bulk Metal Glass

Bulk metallic glass (BMG) is a kind of metallic-like material with amorphous structure, and Fe-based amorphous material is one of the most promising commercial BMGs due to its good soft magnetic properties, such as high saturation magnetization, low coercivity, high permeability, and so on. However it is difficult to fabricate a completely amorphous structure by conventional copper mold casting because a very high cooling rate (above10-5K/s) is required for forming amorphous. Besides, most of Fe-base amorphous can not obtained unless using high purity raw materials, which raises the cost and limits its practical applications. In this thesis, we try to fabricate the Fe-based amorphous using industrial raw materials with relatively low purity and cost by means of copper mold casting and melt spinning. The glass forming ability (GFA), thermal stability and magnetic properties of the Fe-based BMGs were investigated.A series of (Fe48Cr15Mo14C15B6Y2)100-xNix (x=0,6,7,8,9) rod-like alloys were prepared by copper mold casting with a critical diameter of6mm. XRD and Raman results indicated that all samples are amorphous except for that of x=9. The super-cooled liquid regions Δ Ts measured by DTA for the samples with x=0,6,7and8are35,24,23and18K respectively, indicating that the GFA decreases with the increase of Ni content. All samples display paramagnetic behaviors.A series of FeCPSiBMo amorphous with high Fe content (above70at%) were investigated. Fe79.4-xCxSi3.5B5.1P8.9Mo3Mn0.1(x=4.2、5.2、7.0) alloys were prepared using raw materials with industrial purity by copper mold casting. It should be mentioned here that the Mn content comes from the impurity of the raw materials, does not a special doped element. It is revealed that the sample with x=5.2shows the highest GFA with a critical diameter up to4mm, and a large super-cooled liquid region of43K. All the samples exhibit good soft magnetic properties with low coercivity less than204A/m and high saturation magnetization over1T.Fe74.2C5.2Si3.5B5.1P8.9Mo3Mn0.1alloys were produced by melt spinning under different rotating speeds, and then annealed in vacuum at different temperatures (below glass transition temperature (Tg), between Tg and crystallization temperature (Tx), higher than Tx) for different time (10,20,30, and40min). The results showed that the optimum annealing temperatures are between Tg and Tx, and the optimum annealing time is10min.