- 學位論文
鐵-9鋁-30錳-1.2碳-5鈦合金相變化
Phase Transformations of the Fe-9Al-30Mn-1.2C-5Ti Alloy
摘要
本文主要係利用掃描式電子顯微鏡(SEM)與穿透式電子顯微鏡(TEM)等技術，針對析出物在α相、γ區，以及α/γ和γ/γ晶界的析出情況進行分析。主要研究結果，如下所示： 1. 鐵–9鋁–30錳–1.2碳-5鈦合金經1150℃固溶處理後，其顯微組織為(沃斯田鐵+肥粒鐵+TiCx)混合相。γ相可觀察到雙晶及差排的存在，其晶格常數a=3.68Å。α相中之D03相變化為α→B2→D03，D03晶格常數a=5.68Å。TiCx呈長方體，晶格常數a=4.32Å。 2. 合金經450℃~550℃短時效處理後，α/γ晶界存在L'12κ相碳化物析出，而在γ/γ晶界則可觀察到B2相析出。另外，沃斯田鐵基地發現TiCx以四方體析出。延長時效處理時間後，細微L'12 相在沃斯田鐵基地析出；在肥粒鐵相(B2)區域中，則有TiCx碳化物析出。此溫度範圍觀察到B2相結構，較一般鐵鋁錳碳合金溫度低，顯示鈦元素降低了B2→D03轉換溫度。 3. 合金經650~750℃時效處理後，在肥粒鐵相中之D03相變化為α→B2→D03。 4. 合金經650℃~750℃時效處理後，晶界存在L12 κ相碳化物析出，並無肥粒鐵相(D03)析出物被觀察到。 5. 合金在850℃以上時效處理，除TiCx碳化物外，並無析出物被觀察到。
並列摘要
The purposes of the present studies are to investigate the precipitation on the grain boundaries for the Fe-9Al-30Mn-1.2C-5Ti alloy by use of the SEM and TEM. Some main results are described as following: 1. The microstructure of the as-quenched alloy is a mixture of (γ+α+TiCx) phase. Annealing twins and dislocations are found within γ matrix, and aα→B2→D03 transition found within α region. The lattice parameter of the γ, α, and TiCx phase are a=3.68Å,a=5.68Å,and a=4.32Å, respectively. 2. During 450℃~550℃ aged for short time, the L'12 κ-phase carbides are formed on the α/γ grain boundaries, and the B2 phase precipitates found on the γ/γ grain boundaries. TiCx carbides are observed within the γ matrix. Increasing the aging time, some fine κ-phase carbides precipitate within the γ matrix, and TiCx carbides also precipitate within α region. It is noted that the B2→D03 transition temperature is lower than that observation of the Fe-Al-Mn-C alloy system, revealing that the Ti alloy element would play an important role on the B2→D03 transition. 3. Being aged at 650℃~750℃, a α→B2→D03 transition is found within the ferrite region. 4. Being aged at 650℃~750℃, some κ-phase carbides belonging to L12 structure precipitate on the grain boundaries, revealing that carbon element would be random distribution within the κ-phase carbides. 5. Besides the TiCx carbides, no precipitates observed when the specimen aged at temperature above 850℃.