结合数字光学显微镜、扫描电镜(SEM)、高分辨三维X射线衍射、热分析和高温液淬的方法研究共晶灰铸铁的凝固过程和组织演变规律,深入分析石墨的长大动力学及三维连通特征.结果表明:共晶灰铸铁中的石墨结晶初始形貌为球状,异质形核核心为MnS,尺寸为1～2 μm;共晶反应开始时石墨发生变异,长成细小片状石墨,并在共晶团内长大,随后相邻共晶团内的石墨通过中间的液相生长在一起,连接成更大的石墨,共晶反应结束时,大部分石墨在三维上连接在一起,连通率为88.87％;共晶灰铸铁结晶时,石墨长度与时间的关系为、L=-390.56 +555.32(1 e-1/34.52),石墨含量与时间的关系为、C=-17.24 +27.02(1-e-t/41.57).
The solidification process and microstructure evolution of eutectic gray cast iron were studied by means of digital optical microscope,scanning electron microscopy (SEM),high resolution three-dimensional X ray diffraction,thermal analysis and high temperature liquid quenching,besides growth kinetics and three-dimensional connectivity of the graphite were analyzed deeply.The results show that the initial shape of graphite in eutectic gray cast iron is spherical,and the nucleation core of the graphite is mainly MnS,which size is less than 2 μm;the spherical graphite mutates into fine flake graphite when the eutectic reaction starts,and the fine flake graphite grows up in the eutectic cells,then the graphite in the adjacent eutectic cells grows together through the liquid phase forming larger graphite,most of the graphite connects together in three dimensions at the end of eutectic reaction,the connection rate is 88.87％;when the eutectic gray cast iron crystallize,the relationship between the length of graphite and the time is、L =-390.56 + 555.32 (1-e-t/34.52),and the relationship between the content of graphite and the time is、C =-17.24 + 27.02 (1-e-t/41.57).
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