高熵合金由於多元添加的關係，在鑄造過程中易產生偏析，導致成份不均勻，影響其鑄造態之性質。為改善此缺點，文獻研發了共晶型高熵合金 AlCoCrFeNi2.1，將高熵合金結合共晶具備流動性佳與均勻性好的優點，在鑄造態即兼具強度與韌性。此外，透過降低合金製備熔點，更有助於降低製程之熱耗成本，也使得高熵合金發展更具潛力。
本研究藉由相模擬預測及元素變量，發現藉由控制 Al、Cr、Fe 含量能抑制 spinodal decomposition 生成，進而於 AlCoCrFeNi 系統中開發新型共晶合金。本研究設計增加鐵之比例，以降低製造成本之共晶高熵合金，針對該成份進行微結構分析與相成份鑑定，透過 Al變量，探討共晶的初析對於機械性質上之影響。
熱性質與制振性質為高熵合金較少被探討之領域，本研究在此進行初步研究。最後，針對本研究開發之成份與 AlCoCrFeNi2.1，比較各方面之性質，以利未來後續之研究。

The compositional inhomogeneity in high-entropy alloys (HEAs) due to containing multiple elements usually results in segregation, which may worsen the mechanical properties of the casting alloys. In recent research, the eutectic high-entropy alloy (EHEA), AlCoCrFeNi2.1, was proposed to deal with the difficulty. By the advantages of eutectic structure, AlCoCrFeNi2.1 shows the great liquidity and castability. Most importantly, the as-cast EHEA displays the prime mechanical strength and ductility at the same time.
In this research, elements modulation and the prediction by simulation software were used to discover a new kind of EHEA in AlCoCrFeNi system. By modifying the concentration of Al, Cr and Fe, we can suppress the existence of spinodal decomposition, and further create a new EHEA with high cost-efficiency by increasing the amount of Fe. The phase identification and microstructure evolution were studied in this research, as well as the mechanical properties. Moreover, the thermal and dynamic properties, which were rarely studied in HEAs, are also studied in this research. Finally, the new EHEA was thoroughly compared with the AlCoCrFeNi2.1 in many aspects, displaying the high potential of EHEAs for application.

致謝 III
摘要 VII
Abstract VIII
目錄 X
圖目錄 XIV
表目錄 XXII
壹、 前言 1
貳、 文獻回顧 3
2-1 共晶系統 3
2-2 高熵合金 5
2-2.1 高熵合金的定義 5
2-2.2 高熵合金的四大核心效應 6
2-2.3 AlCoCrFeNi 合金系統 13
2-3 共晶型高熵合金 17
2-3.1 AlCoCrFeNi2.1 微結構 19
2-3.2 AlCoCrFeNi2.1 機械性質 22
2-4 Spinodal decomposition 25
2-4.1 基本定義 25
2-4.2 高熵合金中之spinodal decomposition 28
2-5 制振材料之性質 31
2-5.1 材料之制振機制 32
2-5.2 阻尼性質表示種類 32
2-5.3 制振合金之阻尼機制 37
2-5.4 AlxCoCrFeNi 合金制振表現 42
參、 研究方法 46
3-1 實驗流程圖 46
3-2 實驗試片製備 47
3-2.1 合金原料配製與真空電弧熔煉 47
3-2.2 室溫冷滾軋加工 48
3-3 微結構與晶體繞射分析 49
3-3.1 X光繞射分析 (XRD) 49
3-3.2 掃描式電子顯微鏡 (SEM) 49
3-3.3 穿隧式電子顯微鏡 (TEM) 50
3-4 機械性質分析 51
3-4.1 硬度試驗 51
3-4.2 壓縮試驗 51
3-4.3 室溫拉伸試驗 51
3-5 其他性質分析 53
3-5.1 相模擬分析 (Thermo-Calc Software) 53
3-5.2 合金物性模擬 53
3-5.3 制振性質分析 (DMA) 55
3-5.4 熱性質分析 56
肆、 結果與討論 57
4-1 AlCoCrFeNi2.1 合金成份之變量討論 57
4-1.1 AlCoCrFeNi2.1 合金之熱模擬平衡相圖 57
4-1.2 不同元素變量對 AlCoCrFeNi2.1 成份之影響 59
4-2 AlCoCrFeNi 高熵合金系統之變量探討 70
4-2.1 合金設計與相模擬計算 72
4-2.2 雙相高熵合金之微結構與機械性質 76
4-2.3 spinodal decomposition 對共晶結構之影響 85
4-2.4 抑制 spinodal decomposition 之形成 90
4-3 共晶型高熵合晶之成份設計 95
4-3.1 鎳變量對共晶微結構與機械性質之影響 96
4-3.2 鋁變量對共晶微結構與機械性質之影響 103
4-3.3 共晶高熵合金相 TEM 微結構觀察 113
4-3.4 共晶型高熵合金之機械性質 116
4-4 共晶型高熵合金之其他性質研究 125
4-4.1 共晶高熵合金之熱性質分析 125
4-4.2 共晶高熵合金之制振性質分析 139
4-4.3 共晶高熵合金綜合比較 143
伍、 結論 149
陸、 本研究之貢獻 151
柒、 未來研究方向 151
捌、 參考文獻 152

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