低碳铁素体钢中纳米富Cu相由9R向fcc结构的转变

低碳铁素体钢样品经880 ℃加热0.5 h水淬,660 ℃调质处理10 h,然后在400 ℃等温时效11000 h后,利用高分辨透射电镜(HRTEM)和能谱仪(EDS),分析低碳铁素体钢中析出的纳米富Cu相不同晶体结构的特征及联系.观察到长轴约9.5 nm,短轴约6.6 nm的短棒状9R结构的纳米富Cu相,并且均为单斜9R以及呈互为孪晶结构,说明Cu早期析出时优先转变成具有互为孪生关系的单斜9R结构,同时还观察到孪生结构的fcc结构的Cu,以及具有莫尔条纹的非孪晶fcc结构的Cu.表明9R结构除了退孪晶化转变成非孪晶fcc结构外,还可以直接转变成具有孪生关系的fcc结构的纳米富Cu相.

Structure Transformation of Nano-rich Cu Phase Precipitates from 9R to fcc in Low Carbon Ferrite Steel

Low carbon ferritic steel samples were heat treated at 880 ℃ for 0.5 h and then water quenched,tempered at 660 ℃ for 10 h,then isothermal aged at 400 ℃ for 11000 h.The characteristics and relations of different crystal structure of nano-rich Cu phase precipitated in low carbon ferrite steel were analyzed by using high resolution transmission electron microscope (HRTEM) and energy dispersive spectroscopy (EDS).The short rod of monoclinic structure of 9R nano Cu-rich phase with mutualling twin structure were observed, which the long axis is about 9.5 nm, the short axis is about 6.6 nm.It is indicate that the early precipitation of Cu is preferentially transformed into the monoclinic structure of 9R with twin relationship, At the same time, it is observed that the fcc twin structure of Cu, as well as the fcc non-twin structure of Cu with Moire fringe, It is showed that the 9R structure not only retreat into the fcc non-twin structure, also can be directly transformed into fcc structure with twin relationship.