臺灣博碩士論文加值系統

高熵合金通常由五元或五元以上的元素，以5 at.%到35 at.%近等莫耳比的方式形成具有單一固溶相的多元合金。因為結構簡單，所以易於分析、加工、合成、應用，同時擁有優異的物理化學以及機械性質。在高溫時，高熵合金的機械性質可與超合金比擬，有耐熱、耐磨的特性，可用於核工業、交通工具和能源工業等等的所需材料，此外，其生產不需要任何特殊技術，並且可以容易地使用現有設備和技術進行大規模製造，以上原因使其在許多研究領域變得更具吸引力，為開發高性能合金提供新的策略。為了快速開發高熵合金，利用CALPHAD (Calculation of Phase Diagram) 方法搭配高通量計算可算是其中最有效率的做法。本研究利用Pandat軟體並採用PanHEA資料庫，首先計算出17個在可能在Al、Co、Fe、Ni、Ti五元系統中形成高熵合金的點，並從中挑選出六個組成進行實驗，希望形成以FCC固溶相為主的高熵合金。本研究皆使用純度為99.9 wt.%的金屬，再利用電弧熔煉爐來製備合金，之後分別在1000°C下進行72小時的熱處理。最後，分別用場發掃描式電子顯微鏡 (FE-SEM) 及能量分散能譜儀 (EDS) 、X射線繞射儀 (XRD)、穿透式電子顯微鏡 (TEM) 分析其顯微結構及組成。
從各項結果分析可以得知，本研究中六個合金都是以FCC相為主，並同時含有少量的、一至三種其他結構，實驗得到的結果與計算預測相當吻合。本研究還更進一步的做了合金密度、硬度、腐蝕的實驗分析，並以不鏽鋼304以及其他九種合金做為對照組。本研究製作的合金硬度偏高，且擁有比許多常見合金還要低的密度，但較易腐蝕。

High-entropy alloys are defined by alloys those containing five or more random principal major elements with each element atomic concentration is about 5% and less than 35% mixed in equiatomic or near-equiatomic composition. Because of its simple structure, high-entropy alloys are easy to analyze, process, synthesize, and apply. They have excellent physical and chemical properties, especially electrical and magnetic properties, and are also heat-resistant and wear-resistant. At high temperatures, the mechanical properties of high-entropy alloys are comparable to those of superalloys. They can be used in the nuclear industry, materials required for transportation and energy industries. In addition, their production does not require any special technology, and can be easily fabricated on a large scale using existing equipment and technology, which makes it more attractive in many research fields. In order to rapidly develop high-entropy alloys, using CALPHAD method with high-throughput computational method is one of the most efficient practices. The Pandat software with the PanHEA database was used for simulation. First, 17 points which may form a high-entropy alloy in this systems were calculated, and six of them were selected for experiments. It is hoped that a high-entropy alloy mainly composed of FCC structure is formed. In this study, metals having a purity of 99.9 wt.% were used, and the alloys were prepared by an arc melting furnace, followed by heat treatment at 1000°C for 72 hours. Finally, the microstructure and composition of them were analyzed by the field-emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD) and transmission electron microscope (TEM). The experimental result indicated that the six alloys were mainly composed of FCC structure. However, some other structures such as FCC_L12, B2_BCC and H_L21 structures were also formed. The calculation result was mostly consistent with experimental results. Meanwhile, all alloys prepared in this study all had relatively high hardness. Compare to various common alloys, they also had lower densities, but were less susceptible to corrosion.

摘要 I
Abstract II
致謝 III
圖目錄 X
表目錄 XIII
第一章 簡介 1
第二章 文獻回顧 3
2.1 高熵合金 3
2.1.1高熵合金發展 3
2.1.2 高熵合金 4
2.1.3 高熵合金的四大核心效應 6
2.1.3-1 高熵效應 6
2.1.3-2 嚴重晶格扭曲效應 8
2.1.3-3 遲緩擴散效應 9
2.1.3-4 雞尾酒效應 9
2.1.4 高熵合金中的各項參數 10
2.1.5 固溶相之熵與焓 16
2.2 相圖計算軟體 18
2.2.1 CALPHAD方法 (CALculation of PHAse Diagram method) 18
2.2.2 Pandat軟體 20
2.2.3 高通量計算 (High-Throughput Computational Method) 22
2.3 高熵合金的電化學性質 23
2.3.1 腐蝕型態 23
2.3.2 電化學測試 23
2.3.3 極化與鈍化 25
第三章 實驗方法 27
3.1 實驗流程 27
3.2 使用Pandat軟體進行高通量計算 28
3.3 合金組成 30
3.4 合金製備 32
3.5 熱處理 33
3.6 X-ray繞射分析 33
3.7 掃描式電子顯微鏡 34
3.8 合金密度 34
3.6 硬度分析 35
3.9 腐蝕電化學 36
3.10 浸泡試驗 37
第四章 結果與討論 38
4.1 計算結果 38
4.1.1 高通量計算結果─元素組成趨勢 38
4.1.2 高通量計算結果─合金篩選 42
4.1.3 所得高熵合金之各項參數 43
4.2 合金組成及微結構 44
4.2.1 合金1之組成及微結構 (Al11Co26Fe28Ni29Ti6) 44
4.2.2 合金2之組成及微結構 (Al6Co31Fe33Ni24Ti6) 47
4.2.3 合金3之組成及微結構 (Al11Co11Fe33Ni34Ti11) 50
4.2.4 合金4之組成及微結構 (Al6Co31Fe23Ni34Ti6) 53
4.2.5 合金5之組成及微結構 (Al11Co31Fe18Ni34Ti6) 57
4.2.6 合金6之組成及微結構 (Al11Co31Fe33Ni19Ti6) 62
4.3 合金密度分析 65
4.4 合金硬度分析 68
4.5 合金腐蝕性質分析 70
4.5.1 電化學分析 70
4.5.2 經極化試驗後之合金表面分析(SEI) 72
4.5.3 經極化試驗後之合金微結構分析(BEI) 76
4.5.4 浸泡試驗分析 78
第五章 結論 80
Reference 81
附件 87
高通量計算結果列表 87
高通量計算結果之篩選（一） 120
高通量計算結果之篩選（二） 142

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