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  • 學位論文

外加磁場對直接鑄造FePCBSi合金之微觀結構與軟磁特性的影響

The Effect of External Magnetic Field on Microstructure and Magnetic Properties of Directly Cast FePCBSi Alloys

指導教授 : 張文成
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摘要


本實驗以Fe76-xP8.7C7.0B5Si3.3Mx (M=B、C及Si;x=0-5)為起點,研究此成分改變對塊材之非晶形成能力及磁特性的影響。由實驗結果可發現,Si微量添加至x=1時,可以有效增加合金之非晶形成能力。而從B、C添加的實驗結果發現沒有再持續提升合金非晶形成能力的效果。其中以Fe75P8.7C7.0B5Si4.3合金擁有最佳非晶形成能力,其過冷液相區間ΔTx=24 K、約化玻璃轉換溫度Trg=0.62。在磁特性方面,最大非晶圓柱狀棒材3 mm之矯頑磁力Hc=180 A/m。接著以Fe75P8.7C7.0B5Si4.3合金為基底,在鑄造板狀合金時外加一固定磁場,觀察磁場對微觀結構與磁特性的影響。隨著外加磁場的增加晶粒有明顯細化現象,厚度為2 mm之板狀塊材樣品晶粒大小為10-20 nm,而當外加磁場為3 kOe時,晶粒大小降低至2-4 nm。推測外加磁場改變了自由能,使結晶成核之臨界尺寸下降,導致形成非晶能力的提高。其磁特性在未加磁場時,矯頑磁力Hc=682 A/m,而當外加磁場為2 kOe時,其矯頑磁力降低至Hc=159 A/m。隨著磁場的增加,有效的抑制晶粒的成長使得矯頑力隨之降低。當外加磁場增強至3 kOe時,其效力幾乎與外加磁場為2 kOe時相當,顯示磁場對晶粒細化的效力有其極限。將不同外加磁場下鑄造之2 mm薄板,分別量測其電阻率,結果發現隨著外加磁場從0上升至2 kOe,電阻率從175上升至350 Ω-cm,顯示樣品之非晶性確實隨著鑄造磁場增加而上升。本研究中透過成分及製程上的改善,能將Fe75P8.7C7.0B5Si4.3合金製作成最大長14 mm、寬4 mm及厚度為3 mm之非晶板狀塊材。

並列摘要


The effect of the composition on the glass forming ability (GFA) and magnetic properties of the Fe76-xP8.7C7.0B5Si3.3Mx (M = B, C and Si; x = 0-5) bulk metallic glass has been studied. By adding 1% Si to the alloy, the GFA was increased. On the other hand, the GFA and magnetic properties were not enhanced with the addition of the B and C elements. Among the studied alloys, Fe75P8.7C7.0B5Si3.3Si4.3 sample shows the best GFA due to its widely supercooled liquid region ΔTx = 24 K and relatively high reduced glass transition temperature Trg = 0.62. In addition, bulk metallic glass (BMG) with cylindrical shape as large as 3 mm in diameter can be obtained in Fe75P8.7C7.0B5Si4.3 alloy. Furthermore, the effect of external magnetic field on the microstructure and magnetic properties of directly cast FePCBSi alloys were also studied. For bulk sample with 2 mm in thickness, the grain size was refined from 10-20 nm to 2-4 nm with increasing the applied magnetic field from 0 kOe to 3 kOe. It implied that the effect of external magnetic field could change the free energy of the critical nucleus size, leading to the improved GFA. On the other hand, the Hc of the samples without and with 2 kOe applied magnetic field is 682 A/m and 159 A/m, respectively. The enhancement of Hc also verifies the grain size refinement by an additional magnetic field. However, when the external magnetic field increased up to 3 kOe, the enhancemant of Hc is almost identical to that with 2 kOe. It shows that the effect of magnetic field on grain refinement size has a limit at 2 kOe. Meanwhile, the resistivity increased from 175 to 350 Ω-cm as the external magnetic field increasing from 0 to 2 kOe. This phenomenon is also arisen from the field-induced grain refinement.

參考文獻


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