本研究為探討Fe-12.3 wt% Mn-4.13 wt% Al-0.5C合金的亞共析型的相變化情形。合金經過1050℃前處理後，再分別進行900至500℃之時效處理。
經800、700和650℃時效的合金，其沃斯田體的晶界處出現應為初析肥粒體的晶粒。經600及550℃時效之試片，則發現有大量似波來體的組織生成於沃斯田體的晶粒內。於600℃處理之試片中，觀察到初析肥粒體的存在；以及肥粒體與M23C6碳化物往沃斯田體晶粒成長之情形，此為沃斯田體分解為肥粒體加M23C6碳化物的共析反應的證據，故可知本合金於600℃的相變化的形式為：γ → α + M23C6碳化物的亞共析型反應。此似波來體的析出組織所佔的體積分率於550℃時效的試片是最多的。故本合金的恆溫變態曲線的鼻部區域，應於550℃附近。
似波來體組織內的M23C6碳化物，是具面心立方的晶格，其晶格常數為a = 1.057 nm。此M23C6碳化物應是以沃斯田體晶粒(或是少部份的過飽和之BCC麻田散體相)分解為肥粒體加M23C6碳化物的共析反應形式出現。此M23C6碳化物在鐵錳鋁碳合金以共析反應形式出現，是首次被觀察到。而M23C6碳化物與肥粒體間具有以下之特定之方位關係：(011)B//(111)C，[011]B及[112]C之兩軸近似平行，(200)B平面近似平行於(220)C平面。其中下標B為肥粒體，及C為M23C6，而此關係是近似於N-W方位關係。

In this research, we proposed a hypoeutectoid transformation of a Fe-12.3wt%Mn-4.13wt%Al-0.5wt%C alloy aged at low temperatures, ranging from 900 to 500℃. Before the aging processes, the alloy was with a solution-heat-treatment at 1050℃ for an hour.
The grain boundaries were covered with a proeutectoid ferrite for the alloy aged at temperatures below 800℃. For the specimen aged at 900℃, the microstructure of the alloy was similar to that with the solution-heat-treatment. There were pearlite-like structure for the alloy aged below 650℃. The volume fraction of the pearlite-like structure reaches the maximum value for the specimen aged at 550℃. Thus, the nose of the TTT curve of the alloy is around 550℃.
The pearlite-like phase consists of ferrite and carbide. The carbide is not cementite, Fe3C. The carbide is Mn23C6 carbide having FCC crystal structure. The lattice constant of the Mn23C6 carbide is a = 1.057 nm. There is an orientation relationship between ferrite and M23C6 of the type (011)B//(111)C, [011]B near [112]C and (200)B near (220)C, where B and C stand for ferrite and M23C6, respectively. The M23C6 carbide existing in Fe-Mn-Al-C alloys is the first time observation in the form of pearlite-like structure.

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