錳鋁合金鋼具有優良的耐蝕與抗氧化性質，有取代鎳鉻系不銹鋼的潛力，而相變化研究可提供發展錳鋁不銹鋼的基礎。本論文研究二種不同鋁含量的錳鋁鋼相變化情形，其成份分別為鐵-24錳-8.5鋁-0.8碳的合金A與鐵-24錳-4.5鋁-0.9碳的合金B。實驗方法為經1100℃固溶處理與後續低溫恆溫處理。兩合金鋼經1100℃高溫冷卻後，皆發生spinodal相分離與有序化反應：於冷卻過程的高溫區間，高溫沃斯田體相(γ)經spinodal相分離而分解成為兩個貧碳與富碳沃斯田體相(γ’與γ”)，反應式為γ → γ’ + γ”；而富碳沃斯田體相於後續的冷卻過程經由有序化反應而相轉變為L12。我們於經固溶處理的沃斯田體基地發現週期性分佈的L12核，其晶格尺寸約為0.46 nm，所以確認以上的相變化機構。於合金A發現L12之析出上限溫度是介於700℃至650℃之間，而合金B的L12相的析出上限溫度是於300℃附近。所以，鋁含量較低的合金B於較低溫時析出L12相，故推判合金B因低鋁含量之因素，使spinodal相分離與有序化反應發生的溫度降低。

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-24 Mn-8.5Al-0.8C (wt%) and Fe-24 Mn-4.5Al-0.9 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.γ → γ’ + γ” where  is the high temperature austenite, and γ’ and γ” are low temperature austenite phases. The carbon contents of both phases are different. γ’ is low in carbon, and γ” 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. γ” → 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 and κ-carbide.

1. D.A. Porter, K.E. Easterling, Phase Transformations in Metals and Alloys, Nelson Thornes (2008).
2. W.F. Smith, “Structure and Properties of Engineering Alloys”, (1993).
3. W.C. Cheng, H.Y. Lin, Mater. Sci. Eng. A, 323, 462 (2002).
4. S.K. Chen, K.W. Chour, W.B. Lee, C.M. Wan, J.G. Byrne, Mater. Res. Bull., 25, 1115 (1990).
5. K.H. Hwang, C.M. Wan, J.G. Byrne, Mater. Sci. Eng. A, 132, 161 (1991).
6. W.C. Cheng, H.Y. Lin, C.F. Liu, Mater. Sci. Eng. A, 335, 82 (2002).
7. C.J. Wang, Y.C. Chang, Mater. Chem. Phys., 76, 151 (2002).
8. J.W. Lee, C.C. Wu, T.F. Liu, Scripta Mater., 50, 1389 (2004).
9. C.M. Liu, H.C. Cheng, C.Y. Chao, K.L. Ou, J. All. Comp., 488, 52 (2009).
10. T.F. Liu, C.C. Wu, Scripta Meatll., 23, 1087 (1989).
11. T.F. Liu, C.M. Wan, Scripta Metall., 19, 727 (1985).
12. T.F. Liu, J.C. Tasy, Scripta Metall., 21, 1213 (1987).
13. Y.L. Lin, C.P. Chou, Scripta Metall., 27, 67 (1992).
14. D.S. Zhou, G.J. Shiflet, Scripta Metall., 27, 1215 (1992).
15. C.R. Hutchinson, G.J. Shiflet, Scripta Mater., 50, 1 (2004).
16. H. Huang, D. Gan, P.W. Kao, Scripta Metall., 30, 499 (1994).
17. M.C. Li, H. Chang, P.W. Kao, D. Gan, Mater. Chem. Phys., 59, 96 (1999).
18. 陳崧豪，“鐵-20錳-2鋁-0.5碳合金鋼之相變化研究”，國立台灣科技大學機械工程研究所，碩士論文(2008)。
19. 張育仁，“鐵-30錳-1.7鋁-1碳合金鋼之時效相變化研究”，國立台灣科技大學機械工程研究所，碩士論文(2009)。
20. 薛凱云，“鐵-12錳-4鋁-0.5碳合金鋼之亞共析型反應研究”，國立台灣科技大學機械工程研究所，碩士論文(2007)。
21. 吳旻紘，“鐵-31錳-1.5鋁-0.6碳合金鋼之時效相變化研究”，國立台灣科技大學機械工程研究所，碩士論文(2009)。
22. K.H. Han, J.C. Yoon, W.K. Choo, Scripta Metall., 20 , 33 (1986).
23. Y.G. Kim, Y.S. Park, J.K. Han, Metall. Trans. A, 16, 1689 (1985).
24. Y.G. Kim, J.K. Han, E.W. Lee, Metall. Trans. A, 17, 2097 (1986).
25. C.S. Han, W.H. Tian, M. Nemoto, Intermetallics, 1, 209 (1993).
26. N. Boonyachut, The Cellular Transformation in Copper-titanium Age-hardening Alloys, ProQuest LLC (2007).
27. R.C. Ecob, J. V. Bee, B. Ralph, Metall. trans. A, 11, 1407 (1980).
28. R.E. Reed-Hill, “Physical Metallurgy Principle”, (1992).
29. 黃振賢，“金屬熱處理”，文京出版社，第18版(2000)。
30. C.S. Smith, Trans. Am. Soc. Metals, 45, 533 (1953).
31. M.X. Zhang, P.M. Kelly, Meter. Char., 60, 545 (2009).
32. K.H. Kuo, C.L. JIA, Acta Metall., 33 (6), 991 (1985).
33. J. Janovec, M. Svoboda, A. Vyrostkova, A. Kroupa, Mater. Sci. Eng., A, 402, pp. 288-293 (2005).
34. W.K. Choo, J.H. Kim, J.C. Yoon, Acta Mater., 45, 4877 (1997).
35. 劉柏言，“錳鋁鋼層狀組織的-碳化物旁沃斯田體雙晶層之研究”，國立台灣科技大學機械工程研究所，碩士論文(2012)。
36. 林東一，“鐵-21錳-0.5碳合金之麻田散體相變化研究”，國立台灣 科技大學機械工程研究所，碩士論文(2007)。
37. H.J. Kestenbach, Metallography, 10, pp. 189-199 (1977).
38. G.B. Olson, M. Cohen, L.-C. Met., 28, pp. 107-118 (1972).
39. J. Janovec, M. Svoboda, A. Vyrostkova, A. Kroupa, Mater. Sci. Eng., A, 402, 288 (2005).
40. D.N. Shackleton, P.M. Kelly, Acta Metall., 15, 979 (1967).
41. M.X. Zhang, P.M. Kelly, Meter. Char., 60, 545 (2009).
42. J.W. Cahn, Acta Metall., 9, 795 (1961).
43. W.C. Cheng, C.Y. Cheng, C.W. Hsu, D.E. Laughlin, Mater. Sci. Eng. A, 642, 128 (2015).
44. D.E. Laughlin, Acta Metall., 23, 329 (1975).
45. W.A. Soffa, D.E. Laughlin, Prog. Mater. Sci., 49, 347 (2004).
46. W.A. Soffa, D.E. Laughlin, Acta Metall., 37, 3019 (1989)..
47. R. Oshima, C.M. Wayman, Metall. Trans., 3, 2163 (1972).
48. K. Sato, K. Tagawaand, Y. Inoue, Scripta Metall.,22 , 899 (1988).
49. K. Sato, K. Tagawaand, Y. Inoue, Mater. Sci. Eng. A, 111, 45 (1989).
50. K. Sato, K. Tagawaand, Y. Inoue, Metall. Trans. A, 21, 5 (1990).
51. K.H. Han, Mater. Sci. Eng. A, 197, 223 (1995).
52. C.S. Wang, C.N. Hwang, C.G. Chao, T.F. Liu, Scripta Mater., 57, 809 (2007).