本團隊研究鐵錳鋁合金相變化多年，為進一步探討鎳添加於鐵錳鋁合金中所造成的相變化差異，本論文針對成份為鐵-20鎳-15錳-3.7鋁-0.6碳(wt.%)合金之相變化進行研究。熱處理分為前處理的1100℃高溫固溶處理，以及經固溶處理後再於600℃至1000℃的溫度區間進行恆溫處理。此合金鋼經固溶處理後為FCC沃斯田體相(γ)與析出少量BCC+B2共存相，為三相組織；於1000℃至800℃溫度區間，於沃斯田體晶界與基地內同時發生析出型相變化，析出相為BCC相(α)；於700℃至600℃溫度區間，在沃斯田體晶界與基地中析出BCC相、M23C6與M3C碳化物。其中於恆溫處理析出的BCC相經TEM分析確認為BCC與B2兩相共存晶粒， BCC奈米晶粒分布於B2基地內。其成因是因於恆溫處理時γ基地先析出BCC相晶粒，並於水淬降溫過程BCC相晶粒發生自發性相分離而形成貧鎳鋁BCC相(α')與富鎳鋁BCC相(α'')，其反應式如下：α  α' + α''；其中富鎳鋁α''相再於冷卻過程經序化反應，相變化成B2相，其反應式如下：α''  B2；因此，析出α相於降溫冷卻過程的序列反應式如下：α  α' + α''  α' + B2。

Our research teams has been studying the Fe-Mn-Al alloys for many years. In order to further explore the difference in phase changes caused by the addition of Ni to Fe-Mn-Al alloys, this paper will focus on the composition of Fe-20Ni-15Mn-3.7Al-0.6C (wt.%) alloy steel after different heat treatments was analyzed and studied. The heat treatment is divided into solution treatment in which the temperature is kept at 1100°C for 1 hour and then quenched to room temperature, and solution treatment is followed by low temperature constant temperature treatment in the temperature range of 600°C to 1000°C. It is confirmed by this experiment that this alloy steel is a triple-phase with FCC(γ) and (BCC + B2) in Matrix after solution treatment; After heattreatment the precipitated phase is BCC (α) in the grain boundary and matrix at the temperature range of 1000°C to 800°C; At temperature range of 700°C to 600°C, BCC (α), M23C6 carbide and M3C carbide are precipitated in the grain boundaries and matrix. Among them, the BCC precipitated at low temperature and constant temperature treatment was confirmed to be BCC and B2 two-phase coexistence crystal grains by TEM analysis. The BCC (α) are precipitated at the γ matrix during low temperature and constant temperature treatment above 500°C, and undergo spontaneous phase separation (spinodal decomposition) during the water quenching process to the BCC phase (α') transformed into solute-lean BCC phase (α') and solute-enriched BCC phase (α''). The reaction can be written as following: α=α' + α".At cooling procese, disordered supersaturated solution transformed to ordered B2 phase after ordering reaction. The reaction can be written as follows: α"= B2. The overall reactions can be written as follows:α=α' +α"=α' + B2.

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