- 學位論文
高熵合金相圖模擬之研究
The Calculation of Phase Diagrams in High Entropy Alloys
摘要
比傳統合金更具優異性質的高熵合金(high entropy alloys)，由於其高溫熱穩定性、耐蝕性、高強度、硬度、高抗氧化性質，為金屬材料開創一個新的領域，成為一種極具發展潛力 的新興材料。 本研究中以Cu-Co-Ni-Cr-Al-Fe多成分合金系統為主，利用商用軟體Thermal Calc.建立多元成份合金系統資料庫，選用適當的熱力學模組進行相圖的模擬。藉著改變Al成份量、Fe成份量繪 製Cu-Co-Ni-Cr-Al-Fe多元成分相圖。 同時以電弧爐熔煉所設計合金，取樣做金相、電子顯微鏡分析、X-ray分析、熱分析(高溫DSC)進行印証工作。金相觀察的結果該系統合金呈現樹枝狀、與樹枝間結構，並透過EDS分析後發現樹枝間主要是富Cu成分。另外隨著Al的增加(x=1)，樹枝部分 會轉變成網狀的節點分解結構。 接著透過熱分析量測相轉變的溫度，做持溫淬火處理，分析特定溫度下所存在的相；進而評估模擬相圖的準確性。X-ray分析結果顯示各元素間會相互熔成單一的BCC或FCC晶體結構，這與 模擬的相圖結果大致吻合。
關鍵字
高熵合金並列摘要
High entropy alloy, with excellent properties such as high temperature thermal stability, corrosion resistance, high strength, hardness, high oxidation resistance, has improved material properties compared to traditional alloy. High entropy alloy creates a brand-new field of metal materials and becomes a new potential material for development. In this study, the main focus is based on Cu-Co-Ni-Cr-Al-Fe system alloy with multi-components. Commercial software Thermal Calc. is used to set up the database of this multi-components system alloys and to select an appropriate thermodynamic module for the simulation of phase diagrams. Then, by changing the contents of Al and Fe, phase diagrams of Cu-Co-Ni-Cr-Al-Fe multi-components system alloys are plotted. At the same time, the designed alloy is synthesized by an arc-melting and casting method. These samples were observed under optical microscope and then identified by electron microscope analysis, X-ray analysis, and thermal analysis (high-temperature DSC) to verify the result of the simulation. Dendrite and inter-dendrite structures were observed in these systems of alloys. By energy dispersive spectrometry analysis, Cu enriched inter-dendrite structure IV was obtained. With more addition of aluminum (x=1), the dendrite subsequently transformed into net-like structure due to the decomposition of spinodal. The specimens are heat treated and quenched under a specific temperature determined by thermal analysis measurement and analyzed in order to assess the accuracy of the simulated phase diagram. X-ray analysis results indicated that each element would solute reciprocally in a single BCC or FCC crystal structure.Therefore, these results indicated that the experimental phase diagrams reflected roughly with the calculated phase diagrams.