本實驗研究Fe-6.6Mn-3Al-0.35C合金鋼，經冷軋與退火程序，探討在不同冷軋量以及相同冷軋量以單次或多重的冷軋退火製程對於顯微組織及拉伸性質的影響。實驗發現在單次冷軋50%經退火拉伸後得到最高的延伸率(72%)及強延積(73 GPa%)。經由多重冷軋退火拉伸後與單次冷軋退火得到的顯微組織與拉伸性質差異不大。

This study explores the effect of cold rolling and intercritical annealing on the microstructure and tensile properties of a medium manganese steel. The effect of different amount of cold roll reductions followed by intercritical annealing was studied. The effect of multiple combinations of cold rolling and intercritical annealing procedures was also studied. It was found that 50% cold roll reduction had the best tensile properties. Multiple combinations of cold rolling and intercritical annealing procedures gave similar tensile properties. Detailed characterization of the microstructures obtained was performed.

論文審定書 ........................................................................................................................ i
中文摘要 ........................................................................................................................... ii
英文摘要 .......................................................................................................................... iii
圖目錄 .............................................................................................................................. vi
表目錄 ............................................................................................................................. xii
一、前言 ........................................................................................................................... 1
二、文獻回顧 ................................................................................................................... 2
2-1 TRIP 鋼 ............................................................................................................... 2
2-2 逆變態沃斯田鐵 ................................................................................................ 2
2-2-1 逆變態沃斯田鐵的形成機制 ............................................................. 2
2-3 合金鋼中顯微組織與機械性質 ......................................................................... 8
2-3-1 晶粒尺寸的影響 .................................................................................. 8
2-3-2 判定逆變態中 As 及 Af 溫度 ............................................................... 9
2-3-3 冷加工時對於沃斯田鐵的形成與微結構的影響 ............................ 10
2-3-4 晶粒尺寸對於拉伸性質的影響 ........................................................ 11
2-3-5 經多重軋延退火過程產生奈米晶結構之顯微組織及機械性質 .... 14
2-3-6 退火時間對於 TRIP 鋼的影響 ......................................................... 17
2-3-7 兩相區退火錳多相鋼之拉伸行為 .................................................... 20
2-3-8 鋼中 TWIP+TRIP 塑性增強機制 ..................................................... 25
三、研究目的 ................................................................................................................. 31
四、實驗方法 ................................................................................................................. 32
4-1 實驗材料 .......................................................................................................... 32
4-2 拉伸試驗 .......................................................................................................... 32
4-3 金相製備 .......................................................................................................... 32
4-4 顯微組織觀察 .................................................................................................. 33
4-5 背向散射電子繞射 .......................................................................................... 33
4-6 成份分析 .......................................................................................................... 33
4-7 X-ray 繞射分析 ................................................................................................ 33
五、結果 ......................................................................................................................... 35
5-1 顯微組織 ........................................................................................................... 35
v
5-1-1 熱軋板經熱處理過後之顯微組織 .................................................... 35
5-1-2 冷軋退火後之顯微組織 .................................................................... 35
5-2 各不同製程階段以 X-ray 及 EBSD 量測相分率之結果 ............................... 36
5-3 晶粒尺寸 ........................................................................................................... 39
5-4 成份分析 ........................................................................................................... 39
5-5 拉伸性質 ........................................................................................................... 40
5-5-1 不同冷軋量 ........................................................................................ 40
5-5-2 相同冷軋量 ........................................................................................ 41
5-6 拉伸後顯微組織 ............................................................................................... 43
六、討論 ......................................................................................................................... 45
6-1 冷軋對顯微組織及晶粒尺寸的影響 .............................................................. 45
6-2 冷軋對相分率與成份分析的影響 .................................................................. 46
6-3 冷軋量對拉伸性質的影響 .............................................................................. 47
七、結論 ......................................................................................................................... 48
八、參考文獻 ................................................................................................................. 49

1. De Cooman, B.C., Structure–properties relationship in TRIP steels containing carbide-free bainite. Current Opinion in Solid State and Materials Science, 2004. 8: p. 285-303.
2. Jacques, P.J., Transformation-induced plasticity for high strength formable steels. Current Opinion in Solid State and Materials Science, 2004. 8: p. 259-265.
3. Misra, R.D.K.,Zhang, Z., Venkatasurya, P.K.C., Somani, M. C., Karjalainen, L. P., Martensite shear phase reversion-induced nanograined/ultrafine-grained Fe–16Cr–10Ni alloy: The effect of interstitial alloying elements and degree of austenite stability on phase reversion. Materials Science and Engineering: A, 2010. 527: p. 7779-7792.
4. Krauss, G., Fine structure of austenite produced by the reverse martensitic transformation. Acta Metallurgica, 1963. 11: p. 499-509.
5. Misra, R.D.K., Shah, J. S.,Mali, S.,Venkata Surya, P. K. C.,Somani, M. C. and Karjalainen, L. P., Phase reversion induced nanograined austenitic stainless steels: microstructure, reversion and deformation mechanisms. Materials Science and Technology, 2013. 29: p. 1185-1192.
6. Misra, R.D.K., Nayak, S.,Mali, S. A.,Shah, J. S.,Somani, M. C. and Karjalainen, L.P., On the Significance of Nature of Strain-Induced Martensite on Phase-Reversion-Induced Nanograined/Ultrafine-Grained Austenitic Stainless Steel. Metallurgical and Materials Transactions A, 2009. 41: p. 3-12.
7. Takaki, S.,Tomimura, K., Ueda, S., Effect of pre-cold-working on diffusional reversion of deformation induced martensite in metastable austenitic stainless steel. ISIJ International, 1994. 34: p. 522–527.
8. Morrison, W.B., The effect of Grain Size on the Stress-strain Relationship in Low-Carbon Steel. Trans. ASM, 1966. 59: p. 824-846.
9. Morrison, W.B., Miller, R. L., in Ultrafine-Grain Metals. 1970, Syracuse University Press. p. 183.
10. Armstrong, R.W., in Ultrafine-Grain Metals. 1970, Syracuse University Press. p. 1.
11. Porter, L. F., Dabkowski, S.D., in Ultrafine-Grain Metals. 1970, Syracuse University Press. p. 133.
12. Miller, R.L., Ultrafine-Grained Microstructures and Mechanical Properties of Alloy Steels. Metallurgical Transactions, 1972. 3: p. 905-912.
13. McLean, D., Grain Boundaries in Metals. 1957.
14. Ma, Y., Jin, J., and Lee, Y., A repetitive thermomechanical process to produce nano-crystalline in a metastable austenitic steel. Scripta Materialia, 2005. 52: p. 1311-1315.
15. Wang, Y.M. and Ma, E., Strain hardening, strain rate sensitivity, and ductility of nanostructured metals. Materials Science and Engineering: A, 2004. 375-377: p. 46-52.
16. Ma, E., Instabilities and ductility of nanocrystalline and ultrafine-grained metals. Scripta Materialia, 2003. 49: p. 663-668.
17. Han, Q., Zhang, Y., and Wang, L., Effect of Annealing Time on Microstructural Evolution and Deformation Characteristics in 10Mn1.5Al TRIP Steel. Metallurgical and Materials Transactions A, 2015. 46: p. 1917-1926.
18. De Cooman, B.C.,Gibbs, P., Lee, S., Matlock,D.K., Transmission Electron Microscopy Analysis of Yielding in Ultrafine-Grained Medium Mn Transformation-Induced Plasticity Steel. Metallurgical and Materials Transactions A, 2013. 44: p. 2563-2572.
19. Yang, H. and Bhadeshia, H., Austenite grain size and the martensite-start temperature. Scripta Materialia, 2009. 60: p. 493-495.
20. Lee, S. and De Cooman, B.C., Tensile Behavior of Intercritically Annealed 10 pct Mn Multi-phase Steel. Metallurgical and Materials Transactions A, 2013. 45: p. 709-716.
21. Lee, S. and De Cooman, B.C., Annealing Temperature Dependence of the Tensile Behavior of 10 pct Mn Multi-phase TWIP-TRIP Steel. Metallurgical and Materials Transactions A, 2014. 45: p. 6039-6052.
22. Lee, S.,Kim, J., De Cooman, B.C., Effect of nitrogen on the critical strain for dynamic strain aging in high-manganese twinning-induced plasticity steel. Scripta Materialia, 2011. 65: p. 528-531.
23. Hahn, G.T., A Model For Yielding With Special Reference to the Yield-Point Phenomena of Iron and Related BCC Metals. Acta Metallurgica, 1962. 10: p. 727-738.
24. Hu, H., Effect of solutes on lüders strain in low-carbon sheet steels. Metallurgical Transactions A, 1983. 14: p. 85-91.
25. Fujita, H., Miyazaki, S., Lüders deformation in polycrystalline iron. Acta Metallurgica, 1978. 26: p. 1273-1281.
26. Estrin, Y. , Kubin, L.P., in Continuum Models for Materials with Microstructure. 1995, Wiley. p. 365.
27. Lee, S., Estrin, Y., and De Cooman, B.C., Constitutive Modeling of the Mechanical Properties of V-added Medium Manganese TRIP Steel. Metallurgical and Materials Transactions A, 2013. 44: p. 3136-3146.
28. Allain, S.,Chateau, J.P., Modeling of mechanical twinning in a high manganese content austenitic steel. Materials Science and Engineering: A, 2004. 387-389: p. 272-276.
29. Lee, S., Lee, K., and De Cooman, B.C., Observation of the TWIP + TRIP Plasticity-Enhancement Mechanism in Al-Added 6 Wt Pct Medium Mn Steel. Metallurgical and Materials Transactions A, 2015. 46: p. 2356-2363.
30. Lee, S., De Cooman, B.C., On the Selection of the Optimal Intercritical Annealing Temperature for Medium Mn TRIP Steel. Metallurgical and Materials Transactions, 2013. 44: p. 5018-5024.
31. Lee, S., Lee, S.J., Santhosh K., Lee, S. Kyooyoung, DeCooman, B. C., , Localized Deformation in Multiphase, Ultra-Fine-Grained 6 Pct Mn Transformation-Induced Plasticity Steel. Metallurgical and Materials Transactions A, 2011. 42: p. 3638-3651.