臺灣博碩士論文加值系統

本研究以NdFeB MQU-F磁粉自製成MQ2磁石，再將其熱變形成MQ3磁石，探討不同熱壓及熱變形製程對MQ3磁石微觀組織及磁性之影響。第一部分探討熱變形壓縮率、溫度及應變速率的效應影響。利用掃描式電子顯微鏡(SEM)以及X光繞射儀(XRD)觀察晶粒微觀結構和(00L)配向度，並解釋磁特性、配向度以及晶粒形貌三者間之關係。結果顯示由MQU-F所製之MQ3磁石，其最佳製程條件為壓縮率為70 %，且在溫度780 oC下壓製240 s (應變速率為5*10-3 s-1)，磁石磁特性可達Br = 13.4 kG、iHc = 15.5 kOe、(BH)max = 45.1MGOe、iHc+(BH)max = 60.6。第二部分探討MQ3磁石上到下之整體均勻性，將磁石分為未研磨拋光及上下各研磨拋光12.5%厚度後觀察磁特性差異。結果顯示研磨前後磁特性差異最小的MQ3磁石為壓縮率70 %、溫度780 oC下壓製240 s (strain rate為5*10-3 s-1) ，並藉由晶粒形貌的變化和磁石整體配向度的變化來證實MQ3磁石整體均勻性與壓製時間的長短有關係。第三部分探討不同密度之MQ2磁石其均勻性以及晶粒大小及其對最終製成MQ3磁石磁性之影響。發現MQ2磁石密度越大，晶粒越小整體均勻性也越好。其中以密度7.58cm3/g之MQ2磁石晶粒最小(70 nm) 。利用密度7.58cm3/g之MQ2磁石所壓製的MQ3磁石在任何製程下皆比密度7.5cm3/g之MQ2磁石所壓製的MQ3磁石有更好的磁特性，也有更優越的磁晶配向度。該MQ3磁石上下表面各經研磨約12.5%厚度後之磁性可達本研究之最佳值，其Br = 14.4 kG、iHc = 15.8 kOe、(BH)max = 51.5 MGOe，而iHc+(BH)max = 67.3。

In this study, commercial isotropic NdFeB powders, MQU-F, were adopted to make isotropic MQ2 magnets followed by hot deformation process to prepare anisotropic MQ3 magnets. Firstly, the effects of height reduction, deformation temperature and strain rate on the microstructure and magnetic properties of hot-deformed MQ3 magnets were discussed. The intensity ratio of I(006)/I(105) was evaluated from XRD analysis and the grain morphologies were observed by SEM to correlate with the magnetic performance of the MQ3 magnets. Among all samples, the optimal magnetic properties of Br = 13.4 kG、iHc = 15.5 kOe、(BH)max = 45.1MGOe、iHc+(BH)max = 60.6 was obtained in the magnet for 70 % height reduction and hot pressing at 780 oC for 240 s (strain rate 5*10-3 s-1). Secondly, the results show that with the decrease of strain rate, the uniformity of magnetic properties of the magnets was improved. Thirdly, with increasing the density of MQ2 magnets, the grain size could be decreased. The smallest grain size of ~70 nm was obtained for MQ2 magnet with the density of 7.58 g/cm3. In addition, the (00L) texture and magnetic properties of MQ3 magnet, which made from above high density MQ2, were enhanced effectively. The optimal magnetic properties of Br = 14.4 kG, iHc = 15.8 kOe, (BH)max = 51.5 MGOe, and iHc+(BH)max = 67.3 was obtained (70 % reduction, hot pressing at 780 oC for 120 s (strain rate 9.9*10-3 s-1)), if 12.5% thickness in both sides of the magnet was polished.

摘要 I
Abstract II
目錄 III
圖目錄 VII
表目錄 XII
第一章 緒論 1
1-1 前言 1
1-2 磁性材料的分類與簡介 2
1-3 稀土永久磁石簡介 6
1-3-1 永久磁石發展歷史 6
1-3-2 第一代稀土永久磁石-RCo5 7
1-3-3 第二代稀土永久磁石-R2TM17 10
1-3-4 第三代稀土永久磁石-RFeB 11
1-4 R2Fe14B化合物晶體結構之簡介 14
1-5 熱變形NdFeB磁石簡介 16
1-5-1 合金融煉與鑄錠 17
1-5-2 快淬薄帶 17
1-5-3 合金製粉 18
1-5-4 MQ1、MQ2、MQ3製程 20
1-5-5 機械加工與後續處理 23
1-6 熱變形釹鐵硼磁石文獻回顧 24
1-7 研究動機與目的 29
第二章 理論基礎 31
2-1 磁性來源 31
2-2磁滯曲線 33
2-3物質的磁性分類 35
2-4 磁異向性(Magnetic anisotropy) 39
2-5 稀土永磁的矯頑機制 41
2-5-1 反向磁區孕核成長型 42
2-5-2 磁區壁栓固型機制 43
2-5-3 單磁區/微晶型機制 44
2-6 晶粒大小對本質矯頑磁力的影響 45
2-7磁粒子大小對磁性的影響 47
2-8熱變形NdFeB之織構成形機制[54] 49
2-8-1 變形機制 49
2-8-2 流變應力 51
2-8-3 翻轉機制 52
第三章 實驗方法 54
3-1 實驗流程 54
3-2 MQ3磁石製程參數 55
3-3 真空熱壓機 58
3-4 分析與量測 59
3-4-1 切割與研磨 59
3-4-2 B-H tracer 磁性量測 59
3-4-3 XRD-結構鑑定 60
3-4-4 SEM-微觀組織觀察 61
3-5-5 金相觀察 62
第四章 實驗結果與討論 63
4-1 各製程參數對MQ3磁石之磁特性影響 63
4-1-1 壓縮率對熱變形之影響 63
4-1-2 溫度對熱變形之影響 69
4-1-3 壓縮速率對熱變形之影響 75
4-2 探討MQ3磁石均勻度與磁特性之關係 81
4-2-1 微觀結構之均勻性分析 82
4-2-2 由XRD結構分析配向度之均勻性 85
4-2-3 以磁特性變化探討MQ3磁石之均勻性 87
4-3 不同密度之MQ2磁石分析 89
4-3-1 分層分析MQ2磁石之密度 89
4-3-2 MQ2磁石密度與微觀結構之關係 91
4-3-3 以鐵損值解釋MQ2密度與晶粒之關係 93
4-4 以密度最佳MQ2磁石製作MQ3磁石 95
4-4-1 不同MQ2密度熱變形之MQ3磁石 95
4-4-2 溫度對熱變形之影響 101
4-4-3 壓縮速率對熱變形之影響 105
第五章 結論 113
參考文獻 115

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