臺灣博碩士論文加值系統

本實驗主要以商用MQU-F磁粉並參雜2 wt.%不同稀土合金粉，以熱壓熱變形技術製備NdFeB磁石，探討其對磁性及顯微組織之影響。首先，探討R80Al20 (R=La、Ce、Tb、Dy)合金粉之參雜，對不同壓縮率之熱變形NdFeB磁石磁性及微結構之影響。參雜輕稀土合金R80Al20 (R=La、Ce)之磁石在壓縮率為68 %下，皆有最高矯頑磁力，分別為19.3 kOe與20.1 kOe。其中最佳磁性為參雜Ce80Al20，其磁性為Br=12.7 kG，iHc=20.0 kOe，(BH)max=39.6 MGOe。參雜重稀土合金R80Al20(R=Tb、Dy)之磁石在壓縮率為72 %下，磁石皆有最高矯頑磁力，分別為24.2 kOe與23.7 kOe。其中參雜Dy80Al20之磁石，其磁性為Br=13.6 kG，iHc=23.5 kOe，(BH)max=45.8 MGOe，iHc+(BH)max=69.3，每單位重量Dy所能提升iHc量為4.43 kOe/wt.% Dy。第三部分則用(Nd75Pr25)70Cu30合金粉比較參雜法、熱壓時擴散法與熱變形時擴散法對熱變形NdFeB磁石之影響。可發現以熱壓時擴散法後並經熱處理之MQ3磁石，有較好的磁性，Br=13.1 kG，iHc=19.5 kOe，(BH)max=42.5 MGOe。與本實驗室先前參雜(Pr71Nd9Ce20)70Cu30合金粉之磁石比較，本研究所參雜Ce80Al20合金粉之熱變形NdFeB磁石與其有相同矯頑磁力(20.1 kOe)，以經濟考量上則具有成本競爭優勢。另，本實驗參雜Dy80Al20合金粉之熱變形NdFeB磁石iHc (23.7 kOe)較過去含Dy70Cu30(19.4 kOe)與Dy80Ga20(17.7 kOe)之熱變形磁石高，且效益高達4.54 kOe/wt.% Dy。
關鍵字:熱壓熱變形磁石

In this work, magnetic properties and microstructure of hot-deformed NdFeB magnets made by commercial NdFeB MQU-F powders doped with 2 wt.% low-melting rare-earth-containing alloys are studied. At first, the doping effect of R80Al20(R=La、Ce、Tb、Dy) powders is discussed. The enhanced coercivity of 19.3 kOe and 20.1 kOe are found, respectively, for the magnet doped with R80Al20 (R = La, Ce) at reduction ratio of 68 %. The magnets with Ce80Al20 exhibit higher magnetic properties of Br = 12.7 kG, iHc = 20.0 kOe, (BH)max = 39.6 MGOe. The further enhanced coercivity of 24.2 kOe and 23.7 kOe are attained for for the magnet doped with R80Al20 (R = Dy, Tb) at reduction ratio of 72 %, respectively. The magnets with doping Dy80Al20 exhibit the optimal magnetic properties of Br = 13.6 kG, iHc = 23.5 kOe, (BH)max = 45.8 MGOe, iHc + (BH)max = 69.3, the highest iHc enhancement per unit weight percentage of Dy usage could reach 4.43 kOe/wt.% Dy. Besides, (Nd75Pr25)70Cu30 alloy powder was used to compare the coercivity enhancement for the magnets prepared by 3 processes, including above doping, diffusion processes during hot-pressing and hot-deforming. MQ3 magnets after diffusion during hot-pressing exhibit better magnetic properties, Br = 13.1 kG， iHc = 19.5 kOe，(BH)max = 42.5 MGOe. Finally, high coercivity of 20.1 kOe found for the hot-deformed NdFeB magnets doped with Ce80Al20 alloy in this study is comparable to that doped with (Pr71Nd9Ce20)70Cu30 alloy, reported by previous literatures, but it has cost-effective in improving coercivity for economic consideration. Besides, the magnets doped with Dy80Al20 alloy powders exhibit superior coercivity (23.7 kOe) to those with Dy70Cu30 (19.4 kOe) and Dy80Ga20 (17.7 kOe), as previously reported, and most importantly, high efficiency of coercivity enhancemnet of 4.54 kOe/wt. % Dy is attained.
Key word : Hot-deformed magnets

目錄
摘要 I
Abstract IV
目錄 V
圖目錄 IX
表目錄 XIV
第一章 緒論 1
1-1 前言 1
1-2 磁性材料分類與簡介 2
1-3 稀土永久磁石發展與簡介 6
1-3-1 R2Fe14B稀土永磁簡介 7
1-3-2 R2Fe14B化合物晶體結構之簡介 9
1-4 熱變形NdFeB磁石簡介 11
1-5 熱變形磁石之文獻回顧 16
1-6 研究動機與目的 33
第二章 理論基礎 35
2-1 磁性來源 35
2-2 物質的磁性分類 37
2-3 磁異向性(Magnetic anisotropy) 41
2-4 磁滯曲線 43
2-5 稀土永磁的矯頑機制 45
2-5-1 反向磁區孕核成長型 46
2-5-2 磁區壁栓固型機制 47
2-5-3 單磁區/微晶型機制 47
2-6 晶粒大小對本質矯頑磁力的影響 48
2-7 磁粒子大小對磁性的影響 50
2-8 熱變形NdFeB之織構成形機制[49] 52
2-8-1 變形機制 52
2-8-2 流變應力 54
2-8-3 翻轉機制 56
第三章 實驗方法 58
3-1 實驗流程 58
3-2 合金粉製備 61
3-2-1 合金配置 61
3-2-2 電弧熔煉 61
3-2-3 熔融旋焠 62
3-3 MQ3磁石製程參數 63
3-4真空熱壓機 66
3-5 高溫管狀爐熱處理 67
3-6 分析與量測 69
3-6-1 切割與研磨 69
3-6-2 B-H tracer 磁性量測 69
3-6-3 XRD-結構鑑定 70
3-6-4 SEM-微觀組織觀察 71
3-6-5 TEM顯微結構與EDS成分分析 72
第四章 實驗結果與討論 74
4-1 R80Al20(R=La、Ce、Tb、Dy)合金粉參雜效應對熱變形NdFeB磁石磁性及微結構之影響 75
4-1-1 Ce80Al20合金粉參雜效應對熱變形NdFeB磁石磁性及微觀結構之影響 78
4-1-2 La80Al20合金粉參雜效應對熱變形NdFeB磁石磁性及微觀結構之影響 89
4-1-3 Dy80Al20合金粉參雜效應對熱變形NdFeB磁石磁性及微觀結構之影響 98
4-1-4 Tb80Al20合金粉參雜效應對熱變形NdFeB磁石磁性及微觀結構之影響 108
4-1-5 TEM顯微結構分析與EDS成分分析 116
4-2 Ce80Cu20-xZnx（x=0、4、8、12）合金粉參雜效應對熱變形NdFeB磁石磁性及微觀結構之影響 120
4-2-1 合金成分與分析 122
4-2-2 磁特性分析 123
4-2-3 XRD結構分析 127
4-2-4 SEM顯微結構分析 130
4-2-5 TEM顯微結構分析與EDS成分分析 133
4-3 (Nd75Pr25)70Cu30參雜與晶界擴散效應對熱變形NdFeB磁石磁性及結構之影響 135
4-3-1 參雜法對熱變形NdFeB磁石磁性及結構之影響 137
4-3-2 熱壓時擴散法之熱變形NdFeB磁石磁性及結構之影響 141
4-3-3 熱變形時擴散法之熱變形NdFeB磁石磁性及結構之影響 144
4-3-4 綜合比較 147
4-4 綜合比較 150
4-4-1 參雜R80Al20(R= Ce、La、Dy、Tb)合金粉之MQ3磁石綜合比較 150
4-4-2 Ce80Al20與Ce80Cu20-xZnx(x=0、4、8、12)合金粉之MQ3磁石綜合比較 154
4-4-3 R70Cu30與Ce80Al20合金粉之MQ3磁石綜合比較 157
4-4-4 DyR(R=Al、Cu、Ga)合金粉之MQ3磁石綜合比較 158
4-4-5 綜合比較圖 160
第五章 結論 161
第六章 參考資料 163

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