Phase transformations in an Fe-12.0Al-30.0Mn-1.2C alloy

• Main Authors: Chen, shih-hsin, 陳世欣
• Other Authors: Liu Tzeng-Feng
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/32207250917754813186

碩士 === 國立交通大學 === 材料科學與工程研究所 === 85 === Phase transformations in the Fe-12.0Al-30.0Mn-1.2C 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 alloy was austenite phase containing extremely fine (Fe,Mn)3AlC (κ*-carbides) . The κ*-carbides having an L*12-type structure were formed within the austenite matrix during quenching by spinodal decomposition . When the alloy was aged at temperatures ranging from 550℃ to 750℃ , fine κ*-carbides existing in the as-quenched specimen grew preferentially along <100> directions . The κ*-carbides have also an L*12-type structure . However , when the aging temperature was increased to 850℃-950℃ , the well-grown κ*- carbides within the austenite matrix have an L12-type structure . The microstructure of the alloy aged at 1050℃ or above is a single-phase austenite . When the alloy was aged at 550℃ , a γ*D03+κ-carbide transition occurred on the austenite grain boundaries . The κ-carbide is also (Fe,Mn)3AlC carbide . For convience , the κ* and κ-carbides represent the (Fe,Mn)3AlC carbide formed within the austenite matrix and on the grain boundary , respectively . It is noted here that the γ*D03+κ- carbide transition has never before been observed by other workers in the Fe-Al-Mn-C quarternary alloy . With increasing the aging temperature to 750℃ , a γ *B2+κ-carbide transition occurred on the grain boundaries . When the specimen was aged at 850℃ or above , a γ*α+κ-carbide transition occurred on the grain boundaries . It is worthy to note that the κ-carbide has an L*12-type structure at 750℃ or below and an L12-type structure at 850℃ or above .