本論文研究兩種鐵-錳-鋁合金鋼的高溫相變化及低溫時效相
變化。合金的成份如下：合金一為鐵-25.3 錳-4.4 鋁，而合金二為
鐵-24.7錳-4.6鋁-0.03碳。
合金於1350℃為單相的肥粒體相。當溫度介於1300℃至1100℃
之間，兩合金為肥粒體相加上沃斯田體相的雙相組成；而肥粒體相
的組成比例，是隨著溫度的下降而降低。而當溫度低於1100℃時，
合金為單一的沃斯田體相。故此兩合金由1350℃冷卻至室溫的相
變化過程為肥粒體相 沃斯田體相。
合金經1350℃的熱處理後，以急速冷卻方式冷卻，發現合金
內的肥粒體晶粒相轉變為沃斯田體相的方式，是以塊狀相變化的
形式轉變成沃斯田體晶粒；其特徵為合金內的低溫沃斯田體晶粒
全部為不規則形狀。此種由高溫平衡相的肥粒體晶粒經由塊狀相
變化成低溫平衡相的沃斯田體晶粒的相變化方式，是近年來才於
鐵-錳-鋁合金鋼系統中被發現。而本論文則是發現塊狀相變化於合
金內部全面性的發生。當合金於1350℃熱處理後，再以空冷方式
冷卻，於肥粒體晶粒內，發現佈滿了與母材肥粒體晶粒有方向關
係的費德曼狀的沃斯田體析出物。
當合金經1050℃熱處理後，再以淬水方式冷卻至室溫，而後
合金再經600℃以下的時效處理後，於穿透式電子顯微鏡的觀察分
析，發現沃斯田體相晶粒內有新的析出物，此析出物應為新的結
晶相，鑑定此析出物為何種結晶結構，留待未來分析。

Two alloys with wt% compositions of Fe-25.3Mn-4.4Al and
Fe-25Mn-7Al- 0.08C were studied in several heat treatments. Some slabs were
heated at 1350℃ and quenched into cold brine. Irregular massive austenite grains
were observed spread through the specimens. For those with the same heat
treatment but air-cooled, large parent ferrite grains with high density of product
austenite Widmanstätten precipitates were discovered. Full austenite grains were
observed for the slabs heated at 1100 and furnace ℃ -cooled. It was concluded that
the equilibrium phase at 1300 was a single ferrite phase and the stable phase at ℃
low temperatures was a single austenite phase. The phase transformation was a
massive transformation for fast converting the high-temperature ferrite phase to
the low-temperature austenite phase. The irregular shapes of the austenite grains
were one of the characteristics of the massive transformation for the alloy having
been experienced the high-temperature quenching. The massive austenite grains
contained many mechanical twins in various sizes.
For alloys heated at 1350℃ and quenched to room temperature water,
small amounts of the Widmanstätten precipitates appeared at the grain boundaries
of the parent ferrite phase, and all the other space was occupied by the irregular
massive austenite grains. For the two alloys being heated at 1350 and cooled on ℃
the ground, the alloys contained an almost equal amount of austenite
Widmanstätten side-plates and massive austenite grains in the parent ferrite grains.
Thus, for the formation of massive austenite grains and the formation of
Widmanstätten side-plates in the parent ferrite grains, the cooling rate played an
important role. The massive austenite phase dominated in the fast cooling rate,
while the austenite Widmanstätten precipitates preferred the slower cooling rate.
The massive transformation, from ferrite to austenite, was observed
throughout the Fe-Mn-Al alloy and not confined to the specific locations, during
the high-temperature quenching. For the first time, the massive transformation
was discovered in the ferrous alloys for fast converting ferrite to austenite during
the high-temperature quenching.

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