鐵-30錳-8.5鋁-5鈦-1碳合金相變化

Abstract

在本研究中，我們利用掃描式電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM)以及X光能量散佈分析儀(EDS)探討Fe-8.5Al-30Mn-5Ti-1.5C合金之相變化。在淬火狀態下，合金其顯微結構為沃斯田鐵和肥粒鐵之雙相，在沃斯田鐵基地內有大量立方狀的TiC碳化物，此TiC碳化物和沃斯田鐵基地存在著(100)TiC//(100)γ及(110)TiC//(110)γ立方對立方的方向關係；而在肥粒鐵基地內有極細微的D03顆粒和針狀的析出物，此針狀析出物從未在鐵鋁錳合金系統中被發現過，故暫時取名為X-相。因此在淬火狀態下，其存在的相為(γ+TiC)+(α+ D03+X)相。 在550 0C作時效熱處理後，肥粒鐵基地內針狀析出物會逐漸消失，同時具有L´12結構之κ´-(Fe,Mn)3AlC碳化物開始於肥粒鐵基地內析出，且D03顆粒也會逐漸生長粗大。當時效溫度升高到850 0C後，肥粒鐵基地內針狀析出物消失速度更快，且κ´-(Fe,Mn)3AlC碳化物於晶粒內的量會持續增加，而在沃斯田鐵基地內的TiC量也大量增加，且外觀也由立方狀變成圓球狀；並有κ-(Fe,Mn)3AlC碳化物於晶界上生成。最後，當時效溫度升高到950 0C後，在沃斯田鐵基地內TiC量增多外，在肥粒鐵基地內之針狀析出物已完全消失，而在晶粒內之κ´-(Fe,Mn)3AlC碳化物及在晶界上之κ-(Fe,Mn)3AlC碳化物皆有增加的趨勢。 以上這些相變化在Fe-Al-Mn-C合金系統中尚未被其他學者所發現。

Phase transformation in Fe-8.5wt%Al-30wt%Mn-5 wt%Ti-1.5 wt%C alloy have been investigated by means of transmission electron microscopy. In the as-quenched condition, the microstructure of the alloy were dual phase which ferrite phase containing fine D03 particles and needle-like precipitation(X-phase),austenite phase containing cuboid TiC carbides: The orientation relationship between the TiC carbide and the austenite phase was determined to be (100)TiC//(100)γ和(110)TiC//(110)γ, which corresponds to the cubic to cubic orientation relationship. It is noted that in the present study, the coexistence of the fine D03 particles and need-like precipitation(X-phase) in the as-quenched condition have never been found by other workers in the Fe-Al-Mn-Ti-C alloy before.