摘要
利用带蒸汽发生器的同步热分析仪对Fe22Cr5Al3Mo-xY(x = 0、0.15,质量分数,%)合金分别进行1000和1200℃下恒温2 h的高温蒸汽氧化实验.采用XRD、FIB、EDS和TEM观察分析氧化前后样品的显微组织、晶体结构和成分.结果表明,添加0.15%Y使FeCrAl合金在1000℃下的氧化增重速率增大,但可降低FeCrAl合金在1200℃下的氧化增重速率,同时还可以抑制氧化膜表面脊状形貌的形成,并提高了合金氧化膜的厚度均匀性以及界面平整度;2种合金在1000和1200℃的高温蒸汽下恒温2 h后形成的氧化物膜均为α-Al2O3,在Al2O3 膜中平行于氧化膜/基体(O/M)界面的Fe、Cr富集区为hcp-(Cr,Fe)2O3;Fe22Cr5Al3Mo-0.15Y合金在1200℃下恒温2 h后氧化膜中朝向基体一侧生长的富Y氧化物中存在AlYO3、Y2O3和Fe(Cr,Al)2O4尖晶石氧化物.从Y影响氧化膜显微组织演化的角度探讨了Y对不同温度下FeCrAl合金氧化行为的影响机制.
Abstract
An increased temperature causes the breakaway oxidation of zirconium alloys and the loss of structural integrity under the loss of coolant accident(LOCA).Thus,to enhance the inherent safe-ty of nuclear reactors,the idea of developing accident-tolerant fuel(ATF)is proposed.One of the promis-ing candidate materials for ATF cladding is FeCrAl alloy.The theoretical basis and guidance for FeCrAl al-loy's composition optimization can be obtained by investigating the effects of alloying elements on the oxi-dation behavior and mechanism.Thus,the effect of Y on the oxidation behavior of Fe22Cr5Al3Mo alloy in 1000 and 1200℃ high-temperature steam was investigated in this study.Two types of Fe22Cr5Al3Mo-xY(x = 0,0.15,mass fraction,%)alloys,denoted as 0Y and 0.15Y,respectively,were fabricated and oxi-dized in 1000 and 1200℃ high-temperature steam for 2 h,employing a simultaneous thermal analyzer.The microstructure,crystal structure,and composition of the samples before and after oxidation were an-alyzed using XRD,FIB,EDS,and TEM.The findings indicate that adding 0.15%Y increases the weight gain rate of FeCrAl alloy in 1000℃ high-temperature steam,but decreases the weight gain rate of FeCrAl alloy in 1200℃ high-temperature steam.Furthermore,adding 0.15%Y can inhibite the formation of ridge morphology on the surface of oxide film and improve the thickness uniformity and interface flatness of ox-ide film.The oxide films formed on the 0Y and 0.15Y alloys are both α-Al2O3 under the condition of 1000 and 1200℃ high-temperature steam for 2 h.In the Al2O3 oxide film,there is hcp-(Cr,Fe)2O3 paralleled to the oxide/metal(O/M)interface.AlYO3,Y2O3,and Fe(Cr,Al)2O4 are present in the Y-rich oxides growing to-ward the matrix in 0.15Y alloy oxidized in 1200℃ steam.The effect of Y on the oxidation behavior of Fe-CrAl alloy at various temperatures was discussed from the viewpoint of the influence of Y on the micro-structure evolution of oxide film.
维普
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