鐵-35錳-7鋁-4鉻-0.7碳合金相變化

Phase Transformations of the Fe-35Mn-7Al-4Cr-0.7C Alloy

林岳勳(Yueh-Hsun Lin)

指導教授 ： 趙志燁

國立屏東科技大學/工學院/機械工程系所/碩士(2010年)

https://doi.org/10.6346/NPUST.2010.00235

摘要

本文探討鐵35錳-7鋁-4鉻-0.7碳合金之相變化，合金在1050℃/30分鐘固溶處理，其顯微結構為單相沃斯田鐵，其晶格常數a=0.369 nm。於450℃有γ→γ+κ+Y之相變化，其Y相為鈦、鉬及矽元素含量較高之FCC結構，晶格常數a=0.408 nm，在鐵鋁錳碳合金系統中未曾被發現過。550℃時，有γ→γ+Cr7C3→γ+Cr7C3+β-Mn相變化被發現。且沒有足夠證據顯示有α及κ相碳化物。β-Mn晶格常數a=0.610 nm；Cr7C3晶格常數a=1.392 nm，c=0.453 nm。此外，在750℃長時間，則有Cr23C6碳化鉻的析出，其晶格常數a=1.054 nm。於850℃，有Cr7C3碳化鉻與Cr23C6碳化鉻共存之現象。至950℃則只存在Cr23C6碳化鉻。Cr7C3碳化鉻、β-Mn析出物及Cr23C6碳化鉻之存在溫度範圍分別為550~850℃、550~750℃與750~950℃。合金於550℃之晶粒邊界析出現象很少被學者們談論過，其由碳化鉻先產生後，再析出β-Mn。此外，沃斯田鐵雙晶沿< >方向成長，穩定於<111>方向。

關鍵字

鐵鋁錳 ； 沃斯田鐵 ； 晶粒邊界 ； Cr7C3

並列摘要

The main studies of this paper are to analyze the phase transformation of the Fe-35Mn-7Al-4Cr-0.7C alloy. During the 1050℃/30min. solution heated, the microstructure of the present alloy is a single γ phase with lattice parameter a=0.369 nm. Aged at 450℃ for various times, a γ → (γ+κ+Al6Mn) transition can be found within matrix. The lattice parameter of the Al6Mn belonging to FCC structure is a=0.408nm. It is noted here that the observation of Al6Mn precipitate has not been reported in the Fe-Al-Mn-C alloy system. When aged at 550℃ for various times, a γ → (γ+Cr7C3) → (γ+Cr7C3+β-Mn) transition can be found. No evidence that the ferrite phase and κ-phase carbides could be found. The lattice parameters of Cr7C3 and β-Mn phase are a=1.392 nm, c=0.453 nm and a=0.610 nm, respectively. Increasing the aged temperature to 750℃, some DO3 phase particles with lattice parameter a=0.581 nm are found on the grain boundaries. Prolong the aged time, some Cr23C6 carbides with lattice parameter a=1.054 nm are found. Being heated at 850℃, both of the Cr23C6 and Cr7C3 carbides are observed. Meanwhile, the exist temperatures of the Cr7C3, β-Mn and Cr23C6 are in the range of 550-850℃, 550-750℃ and 750-850℃, respectively. Moreover, the twin of the austenite phase can grow along < > direction and stable along <111> direction.

並列關鍵字

Fe-Al-Mn Alloy ； Austenite ； Grain Boundary ； Cr7C3

參考文獻

1. Chih-Yeh, Chao, 2003, Low Density and High Ductility Alloy Steel for Golf Club. U.S. Patent No.6617050.

6. Charles, J., and Berghezan, A., 1981, “Nickel-free Austenitic for Cryogenic Applications: the Fe-23Mn-5Al-0.2C Alloys”, Cryogenic, pp.278-280.

7. Charles, J., Berghezan, A., and Dancoine, P.L., 1981, ”Phase Decomposition of Rapidly Solidified Fe-Mn-Al-C Austenitic Alloys”, Met.Prog., pp.71.

8. Kayak, G.L., 1969, “Fe-Mn-Al Precipitation-Hardening Austenitic Alloys”, Met Sci Heat Treatment.2, pp.95-97.

10. G. L. Kayak, 1959, Met. Sci. Heat., Treat.,11(2), pp.95.