2023-08-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/652440本研究旨在利用合金設計控制TiZrHfNiCu(Co)高熵形狀記憶合金之相平衡與顯微結構，並建立合金成分比例與相變態溫度、超彈性以及形狀記憶效應間之關聯。在本研究中，將採取兩策略以降低TiZrHfNiCu高熵形狀記憶合金中脆性共析反應(Matrix→(Zr, Hf)7Cu10 + Ti2Cu)之比例。策略一為提高Hf/Zr比以降低源自Zr－Cu間板應之共析反應，並同時掌握Zr取代Ti以及Hf取代Ti對於五元TiZrHfNiCu高熵形狀記憶合金之影響。策略二為以第六元合金元素Co分別取代Ni以及Cu元素，以降低Zr－Cu間之反應(Zr－Co之作用力較強)或稀釋Cu之比例以降低共析反應比例。同時亦可掌握Co取代Ni/Cu元素對六元TiZrHfNiCuCo高熵形狀記憶合金性能之影響。本研究中所設計之合金皆將經過充分之熱處理以觀察並研究其相平衡，以確認合金元素設計對於相生成之影響及效果，並與ThermoCalc之熱力學計算結果比對，以做為新合金之顯微結構設計參考。透過本研究，可建立並掌握五元及六元TiZrHfNiCu(Co)高熵形狀記憶合金之組成－相變態溫度－顯微結構－記憶性能四者間之重要關聯，並用於開發具高強度(> 1.6 GPa)與高回復應變(> 5 %)之高性能高熵形狀記憶合金。 This study aims to utilize the high-entropy alloy design concept to control the microstructure and phase formation of TiZrHfNiCu(Co) high-entropy shape memory alloys (HESMAs). The relations between alloy composition, martensitic transformation temperature, superelasticity, and shape memory effect will also be established. In this research project, two strategies will be introduced to reduce the fraction of brittle eutectoid transformation (Matrix→(Zr, Hf)7Cu10 + Ti2Cu) in TiZrHfNiCu SMAs. Strategy 1 is to increase the Hf/Zr ratio of the HESMA to reduce the interaction between Zr and Cu atoms, which is the origin of the eutectoid reaction. At the same time, the influences of the Zr substitute for Ti and the Hf substitute for Ti on the properties of TiZrHfNiCu will be established. Strategy 2 is introducing Co as the sixth alloying element to substitute Ni or Cu atoms, which are expected to reduce the fraction of eutectoid reaction by decreasing the interaction between Zr－Cu (interaction between Zr－Co is stronger) and reducing the Cu content, respectively. Besides, the substitutional effects of Co for Ni and Cu on the properties of the TiZrHfNiCuCo HESMAs can also be developed. All the HESMAs designed in this project will be subjected to heat treatments to analyze their phase equilibrium/formation, and the influences of alloying elements on the microstructure of TiZrHfNiCu(Co) HESMAs will be revealed. Additionally, the microstructures will be compared with the ones calculated by the ThermoCalc software, which will be utilized for designing microstructures of new HESMAs. This research project will develop the relationship between composition－transformation temperature－microstructure－shape memory performance of the TiZrHfNiCu(Co) HESMAs, which will be analyzed and applied to design novel HESMAs with high strength (> 1.6 GPa) and more considerable recoverable strain (> 5 %).形狀記憶合金; 麻田散體相變態; 高熵合金; 相平衡; 顯微結構; 形狀記憶效應; 超彈性;shape memory alloy; martensitic transformation; high-entropy alloy; phase equilibrium; microstructure; shape memory effect; superelasticity