采用机械合金化和热等静压技术制备纳米结构14Cr-ODS铁素体钢, 利用SEM, XRD和EDS等手段分析了机械合金化过程中粉末形态和结构的变化以及合金元素的固溶情况, 通过TEM研究了14Cr-ODS铁素体钢的微观结构及其在短时高温下的稳定性. 结果表明, 元素粉末经机械合金化过程中发生反复的冷焊和断裂导致粉末尺寸先增加(0--2 h)后下降 (2-70 h), 晶粒尺寸随球磨时间的增加而减小, 同时Cr, W和Y2O3等固溶入Fe基体中. 纳米结构14Cr-ODS钢中存在3种析出相: 极高密度的、尺寸在几个纳米的富Y-Ti-O团簇, 少量Y2Ti2O7析出相和块状富Cr-Ti相. 经1250 ℃, 8 h短时高温热处理后, 纳米团簇显示出了良好的稳定性, Y2Ti2O7相的密度增加.
Nano-structured oxide dispersion strengthened (ODS) ferritic steels are the leading candidates of fuel cladding for future fast neutron feeder reactors due to their excellent radiation tolerance and high-temperature creep strength. A 14Cr-ODS steel was prepared by mechanical alloy (MA) and hot isostatic pressing (HIP) methods. The morphology and microstructure of MA powders and the microstructure of 14Cr-ODS steel were characterized by SEM, XRD, EDS and TEM. The results showed that during the MA, the size of powders increases with the increasing milling time (0-2 h), then decreases with the increasing milling time (2-70 h). The grain size decreases with the increasing milling time. The alloying elements and Y2O3 dissolve fully into Fe matrix during MA after 70 h. Three kinds of precipitates are observed in the consolidated 14Cr-ODS steel: very high number density of nanoscale Y-Ti-O-rich clusters, few pyrochlore structure Y2Ti2O7 particles and some Cr-Ti-rich particles. The clusters exhibits good high temperature stability at\linebreak 1250 ℃ for 8 h, while the density of Y2Ti2O7 precipitates increases.
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