鐵錳鋁合金鋼是屬於沃斯田體系不銹鋼，其密度與原料成本是低於傳統的鎳鉻系不銹鋼，故鐵錳鋁不銹鋼是有可能取代部分傳統鎳鉻系不銹鋼而成商業化的低密度不銹鋼。只是要商業化鐵錳鋁不銹鋼是需建立許多資料庫，例如合金鋼相變化的基本資料等。本論文即研究二種鐵錳鋁合金經1300℃與1200℃的高溫熱處理後的相變化情形；以方位影像顯微學(orientation image microscopy, OIM)與穿透式電子顯微鏡(Transmission Electron Microscope, TEM)附加的ASTAR分析儀，分析此二種合金的相組成；並由Factsage軟體所繪製的鐵錳鋁三元相圖，據以探討兩種合金經高溫熱處理後之相變化情形。
合金A的成分為鐵-16.7錳-3.42鋁的三元鐵錳鋁合金，當合金經1300℃高溫淬火處理後，於沃斯田體晶粒內發現BCC麻田散體細碎晶粒，且在部分麻田散體晶粒間存有殘留沃斯田體。經過分析確定此BCC麻田散體晶粒是由原高溫沃斯田體相經由麻田散體相變而成的。此亦符合鐵錳鋁三元相圖的預期，高溫沃斯田體相於低溫時會相轉變為低溫BCC肥粒體相。
合金B成分為鐵-15.9錳-4.2鋁，其經溫度為1300℃的高溫淬火處理後，於肥粒體基地內會出現平行且長條的BCC淬火雙晶。合金B經1200℃空冷處理後，於肥粒體晶界處析出魏德曼組織，此組織原為沃斯田體相晶粒所組成，但於部份的魏德曼沃斯田體晶粒內卻發現細碎的BCC麻田散體晶粒。推論此麻田散體晶粒是於空氣冷卻時，在高溫生成的魏德曼沃斯田體，於較低溫時再次發生麻田散體相變化的結果。故此魏德曼組織是高溫肥粒體相經1200℃以上溫度空冷後，發生二次的相變化的生成物。

Fe-Mn-Al alloys belong to austenite steel system which are low desity and lower than the traditional Ni-Cr steel cost. Thus Fe-Mn-Al alloys have gained much attention as cheap substitutes for some of the conventional Fe-Ni-Cr stainless steels to become commercial stainless steel with the low density. However, to make it become commercial stainless steels require to build the data base such as phase transformation of the alloys. We mainly discuss phase transformation of two different components of Fe-Mn-Al alloys after thermal process from 1300℃ to 1200℃ in this study. We use Factsage software and orientation imaging microscopy(OIM) and transmission electron microscope (TEM)-ASTAR, to identify the phase distribution and the phase transformation differences between these two ternary alloys.
The composition of the alloy A is Fe-16.7Mn-3.42Al (wt%) and the constituent phase at upper temperature 1300℃ is ferrite and austenite phase. Between 1200℃ and 750℃ range is single austenite. Go back to dual phase at lower 750℃. We observed BCC martensite formed in the austenite grains via 1300℃quenching, we also found retain austenite in the BCC martensite. It can proof that BCC martensite is transformed by austenite.
The other composition of steel alloy B is Fe-15.9Mn-3.42Al (wt%). The alloy is single-phase ferrite at temperatures higher than 1200℃. Lower than 1200℃ is ferrite and austenite phase. After 1300℃quenching, ferrite quenching twins appear in the alloy. Twins appear to relieve of the strain energy field that arises from the thermal contraction of the ferritic alloy during quenching. As ferrite quenching twins are induced by the thermal strain energy field relief, they fall in the category of mechanical twins. We also studied alloy B after air-cooling from 1200℃ and found that Widmanstätten austenite precipitate at ferrite grain in the ferrite matrix. It is noteworthy that there are some austenite transform into small fragments of BCC martensite.

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