CoCrFeMnNi等莫耳比高熵合金，由低溫至高溫皆呈現單一FCC相，在此FCC晶格中共有五種不同原子構成五元固溶體，因此非常適合研究高熵合金差排與大量固溶原子的交互作用。為了比較元素個數的影響，本研究同時設計Ni、CoNi、CoFeNi、及CoCrFeNi一元至四元等莫耳比FCC合金進行相同實驗加以比較。
Ni至CoCrFeMnNi五個合金的均質化試片，經過50%、70%及90%的冷輥軋後，微結構觀察發現軋延加工量上升，滑移帶逐漸粗大，且隨著元素個數的增加，滑移帶由波浪狀轉變為平行狀。另外本研究使用X-ray分析法量測，發現疊差能呈下降的趨勢，Ni金屬的疊差能為108 mJ/m2而CoCrFeMnNi合金的疊差能僅6.2 mJ/m2。此一演變使交叉滑移困難，可解釋滑移帶的演變趨勢。
由室溫拉伸曲線的比較，發現降伏強度及伸長率皆隨著元素的添加而提升，顯示在多元效應下，兩項性質皆同時提升，說明高熵固溶強化的優點。此外，在-155 oC的拉伸實驗中，五元合金的強度不但為室溫的2.02倍，且延性卻增加為1.23倍，而Ni金屬的低溫延性卻略為下降，因此FCC高熵合金與傳統FCC金屬對低溫的反應顯然不一樣，本研究認為低疊差能的CoCrFeMnNi合金容易以奈米雙晶變形，且愈低溫欲發達，晶粒的奈米化不但使強度上升且延性也大幅提升。
由300-700 oC高溫拉伸曲線的比較，發現愈多元有愈明顯的鋸齒狀現象，亦即動態應變時效 (dynamic strain aging 簡稱DSA)。一元和二元合金沒有DSA現象；而三元、四元及五元合金在高溫皆有DSA現象。以五元高熵合金為例，300 oC拉伸曲線在高應變區才開始出現DSA，500 oC DSA現象最大，但650 oC下DSA消失。相較於傳統碳鋼，碳原子在300-600 oC間即具有高移動力，足以追趕移動差排而產生DSA現象；然而五元高熵合金的原子皆為置換型，以本實驗室蔡坤佑學長所量的擴散係數來計算，要得到DSA現象，溫度應高達900-1100 oC。針對此，本研究認為差排在多元原子的晶格中，滑移到任一個位置皆同時遭遇許多固溶原子的牽絆，此固溶原子並不需要如碳原子般的擴散追趕，只要當下熱振動 (in-situ)進行小於一個原子距離的移動，即可使差排能量下降，而增加差排再前進的阻力，因而使得DSA現象發生；由於三元等莫耳比合金即開始發生DSA現象，說明此一機制在三元等莫耳比合金即能運作。此外，DSA現象在更高的溫度之所以消失，可歸因於原子的熱振動太大，使現場牽絆 (in- situ pinning)機制變得不明顯。
此外，本研究首次利用中子繞射對高熵合金作分析，發現其表現行為與傳統合金不一樣。高熵合金的彈性係數比平均法則來的小，且對溫度不太敏感。原因來自於晶格扭曲導致原子不在一直線上，使得施加應力後，系統感受的力較小，且因為高溫熱振動必須先抵銷晶格應變，使得彈性係數對溫度不敏感。
最後，本研究對於高熵合金的物理性質做了探討，發現高溫電阻、高溫XRD以及熱傳導係數量測實驗中，皆發現晶格扭曲效應主導了物理性質，導致在一定的溫度區間，對溫度不敏感。

誌謝.......................................................I
摘要.....................................................III
目錄......................................................VI
圖目錄....................................................VII
表目錄....................................................XIX
一、前言....................................................1
二、文獻回顧.................................................3
2.1高熵合金的發展............................................3
2.1.1緣起..................................................3
2.1.2高熵合金的定義..........................................4
2.1.3高熵合金的特點..........................................4
2.1.4高熵合金的研究..........................................7
2.2 FCC 晶體變形系統.........................................7
2.2.1 FCC 晶體滑移系統.......................................7
2.2.2 湯木森四面體 (Thompson’s Tetrahedron)..................9
2.2.3 部分差排..............................................9
2.2.4 Lomer-Cottrell Barrier..............................11
2.3 疊差能.................................................12
2.3.1 疊差................................................12
2.3.2 疊差能...............................................13
2.3.3 疊差能量測...........................................16
2.3.4 疊差能量測方法比較.....................................21
2.4 FCC 晶體疲勞與差排結構...................................22
2.4.1 差排團...............................................22
2.4.2 脈狀組織.............................................23
2.4.3 持續滑移帶...........................................24
2.4.4 差排牆..............................................25
2.4.5 差排胞組織...........................................26
2.4.6 差排滑移取向..........................................28
2.5 低疊差能材料特徵.........................................30
2.5.1 沃斯田型不鏽鋼 310S ..................................30
2.5.2 織構................................................30
2.5.3 輥軋SEM微結構........................................31
2.5.4 輥軋TEM微結構........................................32
2.5.5 變形行為.............................................34
2.5.6 低疊差能特徵統整.......................................35
2.6 動態應變時效 (Dynamic strain aging).....................36
2.6.1 應變時效.............................................36
2.6.2 格隙型 DSA...........................................37
2.6.3 置換型DSA............................................40
2.6.4 鋸齒狀種類...........................................41
3.1 合金製備及實驗流程.......................................43
3.1.1 合金成分設計..........................................43
3.1.2 實驗流程.............................................43
3.1.3 真空電弧融煉..........................................47
3.1.4 均質化處理...........................................48
3.1.5 滾軋................................................48
3.2 X-ray繞射分析..........................................48
3.3 微結構觀察.............................................48
3.3.1 光學式顯微鏡..........................................48
3.3.2 掃描式電子顯微鏡.......................................49
3.4 硬度量測...............................................49
3.5 常溫及高溫拉伸試驗.......................................49
3.6 高溫電阻量測............................................51
3.7 XRD疊差能量測..........................................52
3.8 密度量測...............................................52
四、結果與討論..............................................53
4.1 Ni至CoCrFeMnNi系列合金XRD、SEM、EDS分析..................53
4.1.1 XRD分析.............................................53
4.1.2 金相微結構與EDS 成分分析...............................55
4.1.3 氮氧分析.............................................60
4.1.4 密度量測.............................................61
4.2 輥軋微結構.............................................62
4.2.1 變形微結構...........................................62
4.2.2 Ni至CoCrFeMnNi變形微結構統整..........................64
4.3 常溫機械性質量測........................................67
4.3.1 鑄造態及均質化態硬度試驗................................67
4.3.2 均質化態不同加工量硬度試驗..............................70
4.3.3 常溫拉伸試驗..........................................73
4.3.4 低溫拉伸試驗..........................................74
4.3.5 彈性係數量測..........................................76
4.3.6 機械性質統整..........................................78
4.4 疊差能量測.............................................79
4.4 高溫拉伸試驗............................................86
4.4.1 Ni 高溫拉伸試驗.......................................87
4.4.2 CoNi 高溫拉伸試驗.....................................88
4.4.3 CoFeNi 高溫拉伸試驗...................................89
4.4.4 CoCrFeNi 高溫拉伸試驗.................................91
4.4.5 CoCrFeMnNi 高溫拉伸試驗...............................93
4.4.6 CoCrFeMnNi 不同應變速率探討............................95
4.4.7 DSA機制探討.........................................100
4.5 中子繞射實驗...........................................108
4.5.1 中子繞射架構.........................................108
4.5.2 膨脹係數與彈性係數....................................109
4.5.3 晶格應變與繞射強度探討.................................115
4.6 物理性質量測...........................................123
4.6.1 高溫電阻............................................123
4.6.2 物理性質統整........................................ 127
五、結論..................................................130
六、建議未來研究工作........................................133
七、參考資料...............................................134

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