鐵錳鋁合金鋼具有優良的耐蝕與抗氧化性質，可能有取代鎳鉻系不銹鋼的潛力，而錳鋁合金鋼相變化的研究則是提供發展鐵錳鋁不銹鋼的重要基礎。本論文為研究鐵-28.5-錳-8.8鋁-0.09碳合金鋼之相變化情形。實驗方法為將錳鋁鋼加熱至1100℃、1050℃與1000℃的高溫後以水淬或空冷方式冷卻至室溫。經由穿透式電子顯微鏡(Transmission Electron Microscope, TEM)的分析，確認本錳鋁鋼於1100℃至1000℃的高溫時是為肥粒體與沃斯田體的雙相組織，而沃斯田體的相組成比例是隨溫度的下降而增加。經分析發現於經高溫冷卻後肥粒體與沃斯田體雙相皆發生了spinodal相分離，且肥粒體相更接續產生有序化相變化。由成份分析顯示，沃斯田體晶粒內存在奈米級的零碳與富碳區域，推判其應發生spinodal相分離現象：高溫沃斯田體(γ)經冷卻後，於較低溫時經spinodal相分離而分離成低溫無碳沃斯田體(γ’)與低溫富碳沃斯田體(γ”)，其反應式如下：γ → γ’ + γ”。而於肥粒體晶粒內觀察到奈米級的D03顆粒均勻地散佈於基地內；且成分分析亦發現奈米級的零碳與富碳區域，故推論於冷卻過程中高溫肥粒體(α)分離為低溫零碳肥粒體(α’)與富碳肥粒體(α”)，且富碳肥粒體α”於低溫時發生有序化相變化而形成D03，其反應式如下：α → α’ + α” → α’ + D03。

Fe-Mn-Al steels with excellent corrosion and oxidation resistance have the potential to replace some of the Ni-Cr stainless steel. The phase transformations of the Mn-Al steels play an important role to provide the basic requirement for the development of Mn-Al stainless steels. In this paper, the phase transformations of an Fe-28.5Mn-8.8 Al-0.09 C (wt%) alloy have been studied. The methodology of the experimental procedures includes heating the alloy to temperatures ranging from 1100℃ to 1000℃ and following quenching and/or air cooling to room temperature. The steel is composed of dual phases of ferrite and austenite. The volume fraction of austenite increases as the temperature decreases. We have found the austenite (γ) has undergone spinodal decomposition and decomposes into carbon-lean austenite (γ’) and carbon-enriched austenite (γ”) through the study by the transmission electron microscopy. The spinodal decomposition is as follows. γ → γ’ + γ”. We are the first to report the spinodal decomposition occurs in the alloys. We have also discovered that D03 particles precipitate homogeneously in the ferrite grains. The overall reaction is as follows. α → α’ + D03. We find carbon-lean and carbon-enriched areas in the ferrite grains. We speculate that the ferrite has undergone the spinodal decomposition and transforms into carbon-lean ferrite (α’) and carbon-enriched (α”) at the early stage of the cooling, i.e. α → α’ + α”. Upon further cooling to lower temperature, the carbon-enriched ferrite has undergone the ordering reaction and transforms into D03 phase. The reaction is as follows. α” → D03.

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