鐵-25鉻-6鎳-2.5銅合金相變化

Phase Transformations of the Fe-25Cr-6Ni-2.5Cu Alloys

10.6346/NPUST.2009.00277

林鳳耀

沃斯田鐵 ； 肥粒鐵 ； ε相 ； M23C6 ； austenite ； ferrite ； εphase ； MC carbide ； M23C6 carbide

屏東科技大學機械工程系所學位論文

2009年

碩士

趙志燁

繁體中文

摘要 學號: N9632003 論文題目：鐵–25鉻–6鎳–2.5銅合金相變化 總頁數：54 頁 學校名稱：國立屏東科技大學 系 (所) 別：機械工程系 畢業年月：2010年1月 學位別：碩士學位 研究生：林鳳耀 指導教授：趙志燁 博士 論文摘要內容： 本文主要探討鐵–25%鉻–6%鎳2.5％銅合金鑄件相變化，研究結果顯示：合金鑄件經1050℃/1小時高溫處理後，其顯微組織為沃斯田鐵（γ）與肥粒鐵（α）雙相結構，其中γ相晶格常數a=3.61Å，α相晶格常數a=2.86Å。另外，γ相可觀察到具有兩種方向關係的退火雙晶，分別為：[011]//[011]，(111)//(111)，以及[011]//[014]，(200)//(221)。合金鑄件經1050℃/1小時後，以及400~750℃短時間(8小時內)時效處理後，並無析出物被觀察到。延長時效時間12小時以上，於400~550℃時，於γ相或在α/γ邊界，可發現細微ε相與 M23C6相析出，其相變化為γ→γ+ε+M23C6，其中ε相晶格常數為a＝3.65Å，M23C6相晶格常數為a=10.65Å。而於600~750℃時，則觀察到γ→γ+ MC + M23C6相變態，其中，MC相晶格常數a=4.30Å。由於，晶粒邊界碳化物的析出，而導致合金鑄件硬度上升與延性下降。 關鍵詞：沃斯田鐵、肥粒鐵、ε相、M23C6

Abstract Student ID: N9632003 Title of Thesis: Phase Transformations of the Fe-25Cr-6Ni-2.5Cu Alloys Total Pages: 54 Name of Institute: National Pingtung University of Science and Technology Name of Department: Department of Mechanical Engineering Date of Graduation: .January, 2010 Degree Conferred: Master Name of Student: Feng-Yao Lin Adviser: Dr. Chih-Yeh Chao The Contents of Abstract in this Thesis: The main purposes of the present studies are to analyze the phase transformations of the Fe-25Cr-6Ni-2.5Cu cast alloy. Based on the present studies, some results are described as following. Being solution treatment 1050℃ for 1 hour, the microstructure of the alloy are a mixture of austenite and ferrite duplex phase. The lattice parameter of austenite and ferrite phase are a=3.65Å and a=2.86Å, respectively. In addition, some annealing twin is observed within austenite matrix. The orientation relationship of these twin are found as [011]//[011], (111)//(111), or [011]//[014], (200)//(221). After being solution treatment at 1050℃ for 1 hour then aged at in the range of the 400 and 750℃ for a short time( below 8 hours), no precipitates are found neither the grain boundary or within the matrix. Increasing the aged time to 12 hours or above, a phase transition,γ→γ + ε + M23C6, is found within the γ matrix or on the were α/γ grain boundary when aged at temperature in the range between 400 and 550℃. The lattice parameter ofεand M23C6 phase are a=3.65Å and a=2.86Å, respectively. Moreover, when aged at 600~750℃,a phase transition,γ→γ + MC + M23C6, is found. The lattice parameter of MC phase is a=4.30Å. Due to the precipitation on the grain boundary, the hardness of the ally cast increases and of ductile decreased. Keyword: austenite, ferrite,εphase, MC carbide, M23C6 carbide

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