| Summary: | 碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 98 === The effects of Ta addition on glass forming ability and soft magnetic properties of Fe-Nb-B metallic glass were investigated. The (Fe72Nb4B24)100-xTax (x = 0,1,2,3,4,5 and 6 at.%) ingots were arc-melted under argon atmosphere. A single roller melt-spinning method was employed to produce the alloy ribbons, and the copper mold injection casting was used to prepare 2mm alloy rods. The microstructures of alloy ribbons were shown to be amorphous when Ta additions ranged 0 and 4 at.%. Their ΔTx (= Tx-Tg) increased from 54.5 K (x = 0 at.%) to 70.7 K (x = 3 at.%) and subsequently decreased to 55.9 K (x = 5 at.%). Therefore, the values of ΔTx (= Tx-Tg), Trg (= Tg/Tm or Tg/Tl), γ, Rc, Zc, and Dmax was optimal with 3 at.% of Ta addition. The large ΔTx indicated that the Fe-Nb-B-Ta metallic glass had high glass forming ability and good thermal stability. The saturation magnetization (Ms) of Fe-Nb-B-Ta alloy ribbons decreased from 1.14 T to 0.64 T with increasing Ta from 0 at.% to 6 at.%, and the coercive force (Hc) decreased from 62.5 A/m to 13.2 A/m (x = 1 at.%) and then increased to 65.6 A/m (x=6 at.%). For alloy rods, the Ms decreased from 1.3 T to 0.9 T. Hc decreased from 3118 A/m to 2677 A/m (x = 1 at.%) and then increased to 5962 A/m (x = 6 at.%). Among the alloys investigated, (Fe72Nb4B24)99Ta1 demonstrated a combination of good glass forming ability and optimal soft magnetic properties in either ribbon or rod forms.
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