錳鋁合金鋼具有取代部分傳統鎳鉻系不銹鋼的潛力，而錳鋁鋼相變化之研究則是提供發展錳鋁不銹鋼的重要基礎。本論文是研究兩種成份分別為鐵-25.6錳-6.6鋁-0.56碳與鐵-25.5錳-6.6鋁-0.44碳的錳鋁鋼相變化情形，為發展錳鋁不銹鋼作準備。實驗方法為加熱錳鋁鋼至1100℃做固溶處理與後續低溫恆溫處理。研究顯示經1100℃高溫冷卻的錳鋁鋼內發生了spinodal相分離與有序化相變化之反應，其中高溫沃斯田體相()於冷卻過程的高溫區經相分離而生成兩個低溫沃斯田體相(’ + ”)，其中’為低碳相而”為高碳相，spinodal相分離的反應式為 ’ + ”；而高碳沃斯田體相於後續的冷卻過程再經由有序化相變化生成L12，其反應式為”  L12。於低溫恆溫處理時，於沃斯田體基地內亦發現經由層狀反應生成的層狀的沃斯田體與-碳化物晶粒，此類生成物稱為(+)層狀組織。當溫度下降至750℃至600℃時，於(+)層狀組織內亦會發現層狀-碳化物()與沃斯田體晶粒之間伴隨有沃斯田體雙晶(t)的出現而產生(++t)的層狀組織。

Mn-Al steels have the potential to substitute some of the commercial Ni-Cr stainless steels. For the development of Mn-Al stainless steels, phase transformations play an important role to support the research and development department. We have studied the phase transformations of two Fe-Mn-Al steels with the compositions of Fe-25.6 Mn-6.6 Al-0.63 C (wt%) and Fe-25.4 Mn-6.6 Al-0.38 C. The methodology of the experiments includes heating the steel at 1100℃, quenching to room temperature, and holding isothermally at low temperatures. The results show that the spinodal decomposition and ordering reaction occur in the Fe-Mn-Al steel after heating at and cooling from 1100℃. The reactions are as follows.  ’ + ” where  is the high temperature austenite, and ’ and ” are low temperature austenite phases. The carbon contents of both phases are different. ’ is low in carbon, and ” is high in carbon. The carbon-enriched austenite phase also transforms into L12 phase via ordering reaction upon further cooling to lower temperatures as follows. ”  L12. After the isothermal holding at low temperature, we have also found that κ-carbide appears in the austenite as either grain boundary or cellular precipitate. When the isothermal holding temperatures are below to 750℃, the cellular precipitates are composed of lamellar austenite, -carbide and austenite twins. The lamellar -carbide grains are always accompanying with austenite twins in austenite matrix.

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