鐵鋁錳矽碳和鐵鋁鎳碳合金相變化

Abstract

摘 要 我們利用光學顯微鏡(OM)、穿透式電子顯微鏡(TEM)以及X-光起量散佈儀(EDS)研究鐵-8.0鋁-3.0錳1.5矽-1.5碳，鐵-8.0鋁-10.0鎳-2.0碳和鐵-8.0鋁8.0鎳-2.0碳合金之相變化。 本論文所得結論如下: (一) 鐵-8.0鋁-30.0錳-1.5矽-1.5碳合金在固溶淬火處理後，其顯微結構為沃斯田鐵相與細小的(Fe,Mn)3AlC碳化物。其中細小的 (Fe,Mn)3AlC碳化物是在淬火過程中藉由史賓諾多相分解反應產生。當此合在550℃至1000℃時效處理後隨著溫度增加，其相分解過程依序為(Fe,Mn)3AlC碳化物+D03®(Fe,Mn)3AlC碳化物+B2® (Fe,Mn)3AlC碳化物+α®γ。 (二) 鐵-8鋁-10鎳-2碳合金在淬火狀態下之顯微結構為(γ-κ´-碳化物)。其中細小的κ´-碳化物是在淬火過程中藉由史賓諾多相分解反應產生。當此合金在550℃至1100℃範圍內時效處理後淬火，其相變態過程依序為(κ-碳化物+B2) ® (γ+B2) ®γ+α®γ。 (三) 鐵-8鋁-8鎳-2碳合金在淬火狀態下之顯微結構為沃斯田鐵相與細小的κ´-碳化物。其中細小的κ´-碳化物是在淬火過程中藉由史賓諾多相分解反應產生。此合金在550℃之穩定結構為(α+B2+κ-碳化物)增加時效溫度至850℃，在本合金中可發現粗大B2與細小B2的共存。當時效溫度增加至950℃，粗大κ-碳化物與細小κ´-碳化物在沃斯田鐵相中形成，而且在肥粒鐵相中可以發現淬火過程中產生的α®B2連續規律化相變化反應。此合金在1050℃或更高溫度的顯微結構為單一的沃斯田鐵相。

ABSTRACT The phase transformations in the Fe-8Al-30Mn-1.5Si-1.5C alloy, Fe-8Al-10Ni-2C alloy and Fe-8Al-8Ni-2C alloy have been examined by means of OM, STEM and EDS. As a result the following conclusions have been presented. (1) When the Fe-8Al-30Mn-1.5Si-1.5C alloy was solution heat-treated and quenched, the microstructure was austenite phase containing fine (Fe,Mn)3AlC carbide. The fine(Fe,Mn)3AlC carbide were formed by spinodal decomposition during quenching. After being aged at temperatures ranging from 550℃ to 1000℃ as the aging temperature increased, the phase transition sequence were found to be (Fe,Mn)3AlC carbide + D03 à (Fe,Mn)3AlC carbide + B2 à (Fe,Mn)3AlC carbide + α à γ. (2) In the as-quenched condition, the microstructure of Fe-8Al-10Ni-2C alloy was (γ+ κ'-carbides). The fine κ'-carbides were formed by spinodal decomposition during quenching. When the alloy was alloy was aged at temperatures ranging from 550℃ to 1100℃ for a longer time and then quenched, the phase transition sequence as the aging temperature increased was found to be κ-carbides +B2 à γ+B2 à γ+ α à γ. (3) In the as-quenched condition, the microstructure of the alloy was austenite phase containing κ'-carbides formed by spinodal decomposition during quenching. When the alloy was aged at 550℃, the stable microstructure was (α+B2+κ'-carbides). Increasing the aging temperature to 850℃, the coexistence of the large and fine B2 particles could be observed in the present alloy. As the aging temperature was increased to 950℃, both coarse κ-carbides and fine κ'-carbides could be formed within the austenite matrix, and a αàB2 continuous ordering transition could be detected within the ferrite phase during quenching from 950℃. When the alloy was aged at 1050℃, the stable microstructure was (γ+ α). The single austenite phase could be observed in the alloy aged at 1150℃ or above.