中文摘要：

通过表面机械研磨处理（SMAT）在低活化铁素体钢的表面形成了一层纳米晶．TEM和XRD结果显示，SMAT后的表层组织为纳米晶．550℃的回火实验结果显示，SMAT后的纳米晶具有良好的热稳定性；回火120min后的晶粒异常长大，回火240min后的晶粒比较均匀（约250nm）．SMAT后试样表层碳化物的衍射峰变宽变弱，表明SMAT过程中碳化物被细化，HRTEM观察显示SMAT后的表层组织中存在细小的MC类型碳化物；根据XRD结果，计算了M23C6和MC碳化物的晶格常数分别为1．0631和0．4306nm．由于测试机理和测量深度不同以及纳米组织的尺寸随着深度变化，利用XRD和TEM检测的晶粒尺寸不同，而TEM照片能更准确地反应晶粒的实际尺寸．

英文摘要：

Nanocrystalline grains in the surface of reduced activation ferrite/martensite （RAFM） steel were produced by means of surface mechanical attrition treatment （SMAT）. Analysis results of XRD and TEM showed that grains after SMAT were nanocrystalline. Experiment results after annealing at 550 ℃ showed that the nanocrystallines were stable. Abnormal grain growth was observed from the TEM images after tempered for 120 rain, and the grain sizes became uniform after tempered for 240 rain （about 250 nm）. The XRD diffraction peaks of carbides became weaker and boarder indicated that carbides in the surface layer became smaller after SMAT, and smaller MC type carbides were found from HRTEM images after SMAT. The lattice parameters of M23C6 and MC were 1.0631 and 0.4306 nm calculated from the XRD results. The differences of grain sizes obtained by XRD and TEM could be attributed to the different testing mechanism, different measuring depths and the depth-dependent nanocrystalline microstructure, and results obtained by TEM were more accurate to reveal the real grain size.