本論文針對鐵-20鎳-4.5鋁-1.0碳(wt.%)合金鋼經不同熱處理後產生不同組成與其對應的相變化作分析研究。熱處理分為：高溫1100℃持溫1小時後淬火至室溫水的固溶處理、固溶處理再經淬入液態氮的深冷處理、與固溶處理再於500C至1000C的溫度區間進行恆溫處理。固溶處理後的鎳鋁鋼為單一FCC沃斯田體相(γ)；經深冷處理的金相組織轉變成在沃斯田體基地內出現板狀晶粒的BCT麻田散體；所以，於本鎳鋁鋼形成麻田散體的起始溫度(Ms)是介於零下176℃至室溫間，且於板狀麻田散體晶粒內分佈著細小的BCT麻田散體的機械雙晶晶粒。本鎳鋁鋼於1000℃至750℃的溫度區間，在沃斯田體晶界與晶粒內同時發生析出型相變化，析出顆粒狀分佈的有序B2晶粒，其為含富鎳與富鋁的相。當恆溫處理溫度低於750℃，微細的(Fe,Ni)3AlCxκ碳化物會在沃斯田體基地中析出。在鄰近κ碳化物附近的沃斯田體基地的鎳和碳擴散至碳化物而被吸收，造成臨近沃斯田體基地的鎳與碳含量之濃度下降，而有鎳與碳濃度梯度的產生，使其麻田散體轉換溫度(Ms)升高，並在冷卻後出現麻田散體。

Phase transformations and microstructure changes of an Fe-20 Ni-4.5 Al-1.0 C (wt.%) alloy have been studied through different heat treatments. The heat treatment conditions were divided into: solid solution for 1100℃ for 1 hour then water quenching to room temperature followed by quenching to liquid nitrogen and constant temperature treatment in the range from 500℃ to 1000℃. The results showed that the alloy exhibits two kinds of microstructure; a single FCC structure austenite phase after solution treatment and a plate-like of BCT martensite structure which appeared in austenite matrix after cooling with liquid nitrogen. It was found that, the starting temperature (Ms) of the formation of plate-like of BCT martensite is between minus 176°C and room temperature, and there are smaller mechanical double grains distributed in grains. In the temperature range of 1000℃ to 750℃, a large number of nickel-aluminum rich of B2 precipitates along the grain boundaries and in the grains of the austenite matrix. At temperature is lower than 750°C, it was observed that fine (Fe,Ni)3AlCx carbides precipitates grew in the austenite (γ), This was found to be attributed to nickel and carbon elements in austenite matrix being absorbed by the κ-carbide,, resulting in decreasing the concentration of nickel and carbon near the austenite matrix, finally, the transition temperature (Ms) increased, and the martensite appears after water quenching.

參考文獻
[1] Mulyawan, A., et al. "Interpretation of Fe-rich part of Fe–Al phase diagram
from magnetic properties of A2-, B2-, and D03-phases." Journal of Alloys and Compounds, (2020) 8(34): 155-140.

[2] Walnsch, A., et al. "Thermodynamics of martensite formation in Fe–Mn–
Al–Ni shape memory alloys." Scripta Materialia, (2021) 9(22): 6-31.

[3] Odqvist, J., et al. "On the transition to massive growth during the γ→α
Transformation in Fe–Ni alloys." Scripta Materialia, (2005) 7(2): 193-197.

[4] Kopeček, J., et al. "Ordering in the sublattices of Fe3Al during the phase
transformation B2↔D03." Intermetallics, (1999) 7(12): 1367-1372.

[5] Xiao-hui, Z., et al. "Effects of aging and irradiation on Fe-Ni-Al alloy."
Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms, (2021) 5(9): 55-59.

[6] Sanders, W., et al. "Deformation behaviour of perovskite-type phases in the system Fe-Ni-Al-C. I: Strength and ductility of Ni3AlCx and Fe3AlCx alloys with various microstructures." Intermetallics, (1997) 5(5): 361-375.

[7] Liu, T. F., et al. "Phase transformations in an Fe-8Al-10Ni-2C alloy." Scripta Materialia, (2001) 44(2): 257-262.

[8] Eleno, L., et al. "Assessment of the Fe–Ni–Al system." Intermetallics, (2006) 14(10): 1276-1290.

[9] Chen, H. T., et al. "Rapidly solidified Fe-Ni-Al-C alloys: Metastable phase
formation." Materials Science and Engineering, (1988) 38(4): 277-285.

[10] Porter, D. A., et al. "Phase Transformations in Metals and Alloys." (2008).

[11] Cheng, W. C., et al. "Phase transformation of the L12 phase to kappa-
carbide after spinodal decomposition and ordering in an Fe–C–Mn–Al austenitic steel." Materials Science and Engineering, (2015) 642(26): 128-135.

[12] Couzinié, J. P., et al. "High-temperature deformation mechanisms in a BCC+B2 refractory complex concentrated alloy." Acta Materialia, (2022) 23(8): 155-160.

[13] Lee, J. S., et al. "The microstructure of discontinuously precipitated lamellae in an austenitic Fe-42.4 Ni-4.15 Al-0.45 C alloy." Metallurgical and Materials Transactions A, (1993) 24(4): 1039-1047.

[14] Inoue, A., et al. "Formation of ductile Ni3Al type compound in Fe-(Ni,Mn)
-Al-C system by splat quenching." Transactions of the Japan Institute of Metals, (1979) 20(3): 468-471.

[15] Soffa, W. A., et al. "Decomposition and ordering processes Involving thermodynamically first-order→disorder transformations." Acta Metallurgica, (1989) 11(7): 68-79.

[16] Aaronson, H. I., et al. "Mechanisms of diffusional phase transformations in metals and alloys." CRC Press, (2016) 18(5): 555-568.

[17] Sinning, H. R., et al. "Cyclic deformation of spinodally decomposed Cu-4 at.%Ti single crystals and polycrystals." Materials Science and Engineering, (1982) 55(2): 247-256.

[18] Lee, J. S., et al. "The microstructure of discontinuously precipitated lamellae in an austenitic Fe-42.4 Wt Pct Ni- 4.15 Wt Pct Al-0.45 Wt Pct C alloy." Metallurgical Transactions, (1993) 24(5): 1039-1047.