鐵錳鋁碳合金被視為能代替鉻鎳系不鏽鋼之經濟鋼種，有「窮人的不鏽鋼」之美譽。本論文研究Fe-30 Mn-9 Al-0.12 C (合金A)與Fe-15 Mn-9 Al-0.15C (合金B)，以1300℃與1200℃進行持溫30分鐘的高溫處理。當溫度於1300℃的時候，合金為單相肥粒體，而溫度於1200℃的時候，則為雙相結構，並可在晶界析出物(GBAs)上觀察到具雙晶的沃斯田體晶粒。以空冷方式降溫，兩合金皆可觀察到魏德曼組織(Wid.)自GBAs生成，且合金B的Wid.少於合金A；而以水淬冷卻的試片則都可見針狀麻田散體。其後對空冷試片進行穿透式電子顯微鏡分析，於Wid.中，僅於合金B可觀察到L12相析出物，並可於面掃描成分分析觀察到鋁與碳都有相互吸引的叢聚現象，推測在序化生成L12相之前有spinodal相分離發生；另可於合金A與B的肥粒體基地中觀察到D03相析出物，以面掃描成分分析，也可觀察到鋁元素有相互吸引的叢聚現象，亦可推測有spinodal相分離發生於序化生成D03相之前。故可得於Wid.中的相變化式：Wid. (γ) → Wid. (γ′ + γ′′) → Wid. (γ′ + L12)，以及於肥粒體基地中的相變化：α → α′ + α′′ → α′ + D03。

Fe-Mn-Al-C alloy was regarded as an economical steel that can replace Cr-Ni stainless steel, and has the reputation of "the poor man's stainless steel". The thesis studies Fe-30 Mn-9 Al-0.12 C (alloy A) and Fe-15 Mn-9 Al-0.15C (alloy B). The high temperature treatment was carried out at 1300℃ and 1200℃ for 30 minutes. When the temperature is 1300℃, the alloy is a single-phase ferrite, and when the temperature is 1200℃, it has a dual-phase structure, and twin-crystal austenitic crystals can be observed on the grain boundary allotriomorphic (GBAs). The Widmanstätten structure (Wid.) formed from GBAs can be observed in both alloys by air cooling, and the Wid. of alloy B is less than that of alloy A; while the specimens cooled by water quenching can be observed acicular martensite. Then analysis the AC samples by TEM. For both of them, the precipitation of D03 phase could be observed in the BCC matrix, and the precipitation of L12 phase in alloy B could only be observed in the Wid.. Used STEM for mapping analysis, the clustering of aluminum could be observed in the surface scanning in BCC matrix, and the clustering of aluminum and carbon could be observed in Wid.. Thus, it could be speculated that the spinodal decomposition occurred before the ordering reaction, and known that the phase transformation formula is: Wid. (γ) → Wid. (γ′ + γ′′) → Wid. (γ′ + L12) and α → α′ + α′′ → α′ + D03.

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