耐火高熵合金具有良好機械性質及高溫穩定性。本實驗利用機械合金製程製備多種耐火金屬高熵合金。本研究分為五大部分進行探討，首先針對不同燒結方法對WMoVTi中熵合金之影響。結果顯示高真空燒結可有效降低氧化物粒子形成及顯微結構均一性。第二部分則探討釔元素對於WMoVNb中熵合金研究。添加釔元素能增強合金固溶性，強化材料機械性質。第三部分則進一步探討鈦含量對WMoVCrTi高熵合金之影響。其結果顯示氧化鈦顆粒會隨鈦含量增加而增加，進而影響材料性能。第四部分則探討燒結溫度對WMoVCrTi高熵合金之影響，提高燒結溫度，除了能夠強化高熵合金的固溶性，也可使形成單一BCC固溶相。最後一部分研究於鎢的添加對WMoVCrTi高熵合金之影響。鎢含量的改變，會影響球磨階段合金化與固溶性及最終材料的機械性質。
關鍵字:機械合金、高熵合金、耐火高熵合金

Refractory high entropy alloys (RHEAs) have excellent mechanical properties and high temperature stability. In this study, the different model refectory high entropy alloys produced by mechanical alloying were investigated. There are five main investigations included in this study. Firstly, the effect of sintering methods on WMoVTi medium entropy alloys has been studied. The results indicate that high vacuum sintering can effectively reduce the formation of oxide particles and microstructure homogeneity. Secondly, the WMoVNb medium high entropy alloys adding with a small amount of Y was studied. The addition of Y element can enhance solubility of alloy system and mechanical properties. The third part was further to understand the effect of Ti content on WMoVCrTi high entropy alloys. The results show that Ti-rich oxides increase with increasing Ti concentration, which can alter the material performance. The next part was to investigate the influence of sintering temperatures on WMoVCrTi high entropy alloys. It reveals that a higher sintering temperature can promote solubility of the model high entropy alloys and form a single BCC solid solution phase. The final part was to clarify the effect of W element on WMoVCrTi high entropy alloys. The change of W content can affect alloying processing during ball milling, solubility of alloy system and mechanical properties of final products.
Keyword: Mechanical alloy; high-entropy alloys; refractory high entropy alloys

第1章 緒論 1
1.1前言 1
1.2研究動機 2
第2章 文獻回顧 3
2.1高熵合金 3
2.1.1高熵合金發展及原理 3
2.1.2 嚴重的晶格應變 4
2.1.3 擴散速率降低 4
2.1.4雞尾酒效應 5
2.2耐火高熵合金 5
2.3散佈強化 7
2.4 機械合金 8
2.4.1 機械合金原理 8
2.4.2 機械合金製程 8
第3章 研究方法與實驗步驟 15
3-1 粉末製備 15
3-2 合金成形 15
3-3 合金分析 16
第4章 結果與討論 27
4.1不同燒結方法對WMoVTi中熵合金之影響 27
4.1.1粉體XRD分析 27
4.1.2 塊材SEM與EDS分析 28
4.1.3 塊材XRD分析 29
4.1.4維氏硬度分析 29
4.2釔對於WMoVNb 中熵合金的影響 36
4.2.1粉體XRD分析 36
4.2.2 SEM與EDS分析 37
4.2.3 塊材XRD分析 38
4.2.4維氏硬度分析 39
4.3鈦含量對WMoVCrTi高熵合金影響 47
4.3.1粉體XRD分析 47
4.3.2 SEM與EDS分析 47
4.3.3 塊材XRD分析 48
4.3.4維氏硬度分析 49
4.3.5壓縮應力分析 49
4.4燒結溫度對WMoVCrTi高熵合金影響 60
4.4.1 SEM與EDS分析 60
4.4.2 XRD分析 61
4.4.3維氏硬度分析 62
4.5鎢的添加對WMoVCrTi高熵合金影響 69
4.5.1 粉體XRD分析 69
4.5.2 塊材SEM與EDS分析 69
4.5.3 塊材XRD分析 70
4.5.4維氏硬度分析 71
第5章 結論 79
參考文獻 82

Uncategorized References
1. Murty, B.S., J.W. Yeh, and S. Ranganathan, High Entropy Alloys, in High Entropy Alloys. 2014.
2. 陳振華，陳鼎, 機械合金化與固液反應球磨，pp.52-58, pp.149-150.
3. Chen, T.-K., et al., Nanostructured nitride films of multi-element high-entropy alloys by reactive DC sputtering. Surface and Coatings Technology, 2005. 200(5-6): p. 1361-1365.
4. Yeh, J.-W., Alloy Design Strategies and Future Trends in High-Entropy Alloys. Jom, 2013. 65(12): p. 1759-1771.
5. Tsai, K.Y., M.H. Tsai, and J.W. Yeh, Sluggish diffusion in Co–Cr–Fe–Mn–Ni high-entropy alloys. Acta Materialia, 2013. 61(13): p. 4887-4897.
6. Senkov, O.N., et al., Refractory high-entropy alloys. Intermetallics, 2010. 18(9): p. 1758-1765.
7. Senkov, O.N., et al., Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys. Intermetallics, 2011. 19(5): p. 698-706.
8. Senkov, O.N., et al., Mechanical properties of low-density, refractory multi-principal element alloys of the Cr–Nb–Ti–V–Zr system. Materials Science and Engineering: A, 2013. 565: p. 51-62.
9. Wu, Y.D., et al., A refractory Hf25Nb25Ti25Zr25 high-entropy alloy with excellent structural stability and tensile properties. Materials Letters, 2014. 130: p. 277-280.
10. Pan, J., et al., Microstructure and mechanical properties of Nb25Mo25Ta25W25 and Ti8Nb23Mo23Ta23W23 high entropy alloys prepared by mechanical alloying and spark plasma sintering. Materials Science and Engineering: A, 2018. 738: p. 362-366.
11. Liu, Q., et al., Microstructure and mechanical properties of ultra-fine grained MoNbTaTiV refractory high-entropy alloy fabricated by spark plasma sintering. Journal of Materials Science & Technology, 2019. 35(11): p. 2600-2607.
12. Guo, W., et al., Microstructures and mechanical properties of ductile NbTaTiV refractory high entropy alloy prepared by powder metallurgy. Journal of Alloys and Compounds, 2019. 776: p. 428-436.
13. Yurchenko, N., et al., Structure and mechanical properties of an in situ refractory Al20Cr10Nb15Ti20V25Zr10 high entropy alloy composite. Materials Letters, 2020. 264.
14. Xu, Q., et al., NbMoTiVSi refractory high entropy alloys strengthened by forming BCC phase and silicide eutectic structure. Journal of Materials Science & Technology, 2020.
15. Senkov, O.N., et al., Oxidation behavior of a refractory NbCrMo0.5Ta0.5TiZr alloy. Journal of Materials Science, 2012. 47(18): p. 6522-6534.
16. Gwalani, B., et al., Strengthening of Al0.3CoCrFeMnNi-based ODS high entropy alloys with incremental changes in the concentration of Y2O3. Scripta Materialia, 2019. 162: p. 477-481.
17. Suryanarayana, C., Mechanical alloying and milling. Materials Science 2001.
18. Wang, S., et al., Effect of mechanical alloying on the microstructure and properties of W–Ti alloys fabricated by spark plasma sintering. Powder Technology, 2016. 302: p. 1-7.
19. Xin, S.W., et al., Ultrahard bulk nanocrystalline VNbMoTaW high-entropy alloy. Journal of Alloys and Compounds, 2018. 769: p. 597-604.
20. Kang, B., et al., Ultra-high strength WNbMoTaV high-entropy alloys with fine grain structure fabricated by powder metallurgical process. Materials Science and Engineering: A, 2018. 712: p. 616-624.
21. Chou, T.H., et al., Consideration of kinetics on intermetallics formation in solid-solution high entropy alloys. Acta Materialia, 2020. 195: p. 71-80.