鐵-18 at.%鋁-10 at.%鈦合金之相變化

Abstract

我們利用光學顯微鏡(OM)、穿透式電子顯微鏡(TEM)和X光能量散佈分析儀(EDS)，研究Fe-18at.%Al-10at.%Ti合金的相變化。 Fe-18at.%Al-10at.%Ti合金在淬火狀態下的顯微結構為(A2+D03)相的混合。其中D03相是經由A2 → B2 → (A2+D03)之連續規律化的過程而產生。當我們將此合金在700℃至1100℃的溫度範圍內施以不同時間的時效處理後發現，此合金隨著溫度的增加其一系列相變化過程為A2+D03→A2+D03+C14→B2+C14→A2+C14→A2；值得ㄧ提的是，這一實驗結果從未被其他學者觀察過。此外，當此合金在800℃作1小時的時效處理後，經過擇區繞射圖我們觀察到基底的(A2+D03)相和C14相會有以下的方向關係(0001)C14//(-1-12)m , (-1100)C14//(-110)m , (11-20)C14//(111)m，這一實驗結果在Fe-Al-Ti合金中也從未被發現過。

Phase transformations in an Fe-20at.%Al-8at.%Ti alloy have been examined by means of optical microscopy (OM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometer (EDS). In the as-quenched condition, the microstructure of the Fe - 18at.%Al - 10at.%Ti alloy was a mixture of (A2+D03) phases and the D03 phase was formed by an A2 → B2 → (A2+D03) continuous ordering transition during quenching. When the as-quenched alloy was aged at temperatures ranging from 700℃ to 1100℃, the phase transition sequence as the aging temperature increased was found to be A2+D03→A2+D03+C14→B2+C14→A2+C14→A2. It is noted here that this phase transition has never been observed by other workers in the Fe-Al-Ti alloys before. In addition, when the present alloy was aged at 850℃, the orientation relationship between the C14 precipitate and (A2+D03) matrix was determined to be (0001)C14//(-1-12)m , (-1100)C14//(-110)m , (11-20)C14//(111)m analysed by the above diffraction patterns. This orientation relationship between the C14 precipitate and A2, D03 or B2 matrix has never been reported by other workers in the Fe-Al-Ti alloy systems before.