商用型18% Ni麻時效鋼經由固溶熱處理後，不論冷卻速率快慢皆會轉變成富有極大量差排的麻田散鐵組織。而後進行時效熱處理，從麻田散鐵基地相中析出分布均勻且極小的金屬間化合物，進而阻礙差排滑移來達到強化材料機械性質之目的。
　　本研究目的為將高熵效應應用於麻時效鋼，期望將麻時效剛之工作溫度提高，突破麻時效鋼之工作環境溫度使用之限制。從析出物 η-Ni3(Ti,Mo,Al) 成分以及結合焓的角度，額外添加Hf,Nb,Ta,V,Y,Zr等元素。額外添加 Y ( Yttrium )之系統，因與Ni之結合焓過負，亦即容易結合，導致均質化態即有 Ni-rich 相產生，使 Ms 溫度下降不易產生麻田散鐵相，後續之時效熱處理無法有效的達到析出硬化的效果。Hf與Zr對Fe之固溶度極低，使Laves phase 在鑄造態時則析出於晶界上，對強度沒有太大幫助，但卻對延展性與韌性有可預期的潛在危害。在僅有額外添加 Nb,Ta,V 之合金系統，有較強之固溶強化效果，可減少達到Peak hardness 之時間，但析出強化而增加之硬度值並無顯著增加。
　　從基地相去做改良，結果發現C25 合金於480 oC時效熱處理48小時其 Peak Hardness 可達 677 Hv，C42 合金於480 oC時效熱處理 400小時，其硬度已達747 Hv且尚未過時效，已超越商用 Grade 250 與 Grade 350 之硬度 ( 555 Hv 與 717 Hv )，此兩合金具有高強度結構材料之應用潛力。

18-Ni commercial maraging steel with addition of Hf,Nb,Ta,V,Y,Zr and C-series modified from 18-Ni 250 grade maraging steel were prepared by vacuum arc melting (VAM) and further investigation was carried out on microstructure and mechanical behavior as a function of aging condition. Owning to the negative value of mixing enthalpy between Ni and Y, Ni-rich phase, which would lower the Ms and As value thus causing reversion of austenite and affected the precipitation behavior, existed since homogenization state. Laves phase precipitating at grainboundary deteriorated the mechanical properties for Hf and Zr has little solubility in Fe. With addition of Nb,Ta and V, obvious solid solution strengthening effect was observed and less time was needed to reach the peak hardness. C25 reached the peak hardness of Hv 677 which was higher than 250 garde maraging steel when aging at 480 oC for 48h and C42 reached Hv 747 without any sign of over-aging after 400 hours of aging at 480 oC. C25M10 achieved the hardness of Hv 825 when aging at 480 oC for 24h, which has exceeded the hardness of 350 grade maraging steel.

致謝
Abstract
摘要 I
目錄 III
圖目錄 IX
表目錄 XVII
壹 前言 1
貳 文獻回顧 2
2.1 高熵合金之發展 2
2.2 高熵合金之特色 4
2.2.1 晶體結構 4
2.2.2 擴散速率 4
2.2.3 熱力學 5
2.2.4 強化機制 5
2.2.5 高溫強度 5
2.3 麻時效鋼 6
2.3.1 麻時效鋼之發展演進 7
2.3.2 不同元素對於麻時效鋼之影響與特性 8
2.4 麻時效鋼之材料特性與製程 19
2.4.1 Fe-Ni二元介穩態相圖 21
2.4.2 時效熱處理 ( Aging heat treatment ) 22
參 合金製備與實驗流程 25
3.1 真空電弧熔煉 25
3.2 均質化熱處理 ( Homogenization ) 25
3.3 固溶熱處理 ( Solution treatment ) 25
3.4 時效處理 ( Aging ) 26
3.5 硬度量測 26
3.6 X-ray 繞射分析 26
3.7 微結構 26
3.8 拉伸試驗 27
肆 結果與討論 28
4.1 合金命名與成分設計 28
4.2 Grade250之性質 34
4.2.1 Grade250均質化態之結構與硬度 34
4.2.2 Grade250固溶熱處理態之結構與硬度 36
4.2.3 Grade250時效處理態之結構與硬度 37
4.3 Grade250m之性質 40
4.3.1 Grade250m均質化態之結構與硬度 40
4.3.2 Grade250m固溶熱處理態之結構與硬度 41
4.3.3 Grade250m時效處理態之結構與硬度 42
4.4 Grade350之性質 44
4.4.1 Grade350均質化態之結構與硬度 44
4.4.2 Grade350固溶熱處理態之結構與硬度 46
4.4.3 Grade350時效處理態之結構與硬度 47
4.5 Grade350m之性質 49
4.5.1 Grade350m均質化態之結構與硬度 49
4.5.2 Grade350m固溶熱處理態之結構與硬度 50
4.5.3 Grade350m時效處理態之結構與硬度 52
4.6 Grade350 T4M3之性質 54
4.6.1 Grade350 T4M3均質化態之結構與硬度 54
4.6.2 Grade350 T4M3固溶熱處理態之結構與硬度 57
4.6.3 Grade350 T4M3時效熱處理態之結構與硬度 58
4.7 Grade350 HNTVZ3之性質 60
4.7.1 Grade350 HNYVZ3均質化態之結構與硬度 60
4.7.2 Grade350 HNTVZ3固溶熱處理態之結構與硬度 62
4.7.3 Grade350 HNTVZ3時效熱處理態之結構與硬度 63
4.8 Grade350 HNTVZ2之性質 66
4.8.1 Grade350 HNTVZ2均質化態之結構與硬度 66
4.8.2 Grade350 HNTVZ2固溶熱處理態之結構與硬度 68
4.8.3 Grade350 HNTVZ2時效熱處理態之結構與硬度 69
4.9 Grade350 NTV2之性質 71
4.9.1 Grade350 NTV2均質化態與固溶熱處理之結構與硬度…………….. 71
4.9.2 Grade350 NTV2時效熱處理態之結構與硬度 72
4.10 Grade250 NTV2之性質 74
4.10.1 Grade250 NTV2均質化態與固溶熱處理態之結構與硬度…………………………………………………….…….74
4.10.2 Grade250 NTV2固溶熱處理態之結構與硬度 75
4.10.3 Grade250 NTV2時效熱處理態之結構與硬度 77
4.11 Ni 20之性質 79
4.11.1 Ni 20 均質化態與固溶熱處理態之結構與硬度 79
4.11.2 Ni 20 時效熱處理態之結構與硬度 82
4.12 Ni 22之性質 84
4.12.1 Ni 22 均質化態與固溶熱處理態之結構與硬度 84
4.12.2 Ni 22 時效熱處理態之結構與硬度 86
4.13 Co 4.3 與 Ni 4.3之性質 88
4.13.1 Co 4.3之性質 88
4.13.2 Ni 4.3之性質 90
4.14 C25 之性質 92
4.14.1 C25 固溶熱處理態之結構與硬度 92
4.14.2 C25 時效處理態之結構與硬度 94
4.15 C25M10 之性質 97
4.15.1 C25M10 固溶熱處理態之結構與硬度 97
4.15.2 C25M10 時效處理態之結構與硬度 100
4.16 C42 之性質 103
4.16.1 C42 固溶熱處理態之結構與硬度 103
4.16.2 C42 時效處理態之結構與硬度 104
4.17 C42T 之性質 107
4.17.1 C42T 固溶熱處理態之結構與硬度 107
4.17.2 C42T 時效處理態之結構與硬度 108
4.18 C60 之性質 110
4.18.1 C60 固溶熱處理態之結構與硬度 110
4.18.2 C60 時效處理態之結構與硬度 111
4.19 C77 之性質 112
4.19.1 C77 固溶熱處理態之結構與硬度 112
4.19.2 C77 時效處理態之結構與硬度 114
伍 結論 115
陸 本研究之貢獻 118
柒 建議未來研究工作 119
捌 參考資料 120

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