| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系 === 88 === Phase transformations in the Fe-8Al-12Ni-2C alloy have been examined by means of optical microscopy (OM), scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectrometer (EDS).
When the Fe-8Al-12Ni-2C alloy was solution heat-treated and quenched, the microstructure of Fe-8Al-12Ni-2C alloy was a mixture of (γ＋κ'-carbides). When the alloy was aged at the temperatures from 550℃ to 750℃, transmission electron microscopy examinations revealed that the stable microstructure of (α+ B2+κ-carbide) could be preserved up to 750℃. When the alloy was aged at 850℃ and then quenched, both the coarse and the fine B2 particles could be observed within the ferrite matrix. The coarse and the fine B2 particles were formed during the aging process and the quenching process, respectively. When the alloy was aged at 950℃, both the coarse κ-carbide and the fine κ'-carbides were formed by spinodal decomposition during quenching. We also found that the fine B2 domains with a/2<111> anti-phase boundaries were formed during quenching by αàB2 ordering transition.
When the alloy was aged at 1050℃, the stable microstructure in the present alloy was austenite and ferrite phase. The microstructure of the alloy at 1150℃ or above is a single austenite phase. Other workers in the Fe-Al-Ni-C alloys before have never reported this transition.
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