等温淬火球墨铸铁精细结构分析  

Fine Structure Analysis of Austempered Ductile Iron

作　　者：韩非 徐锦锋[1] 闫启栋 王迎战 HAN Fei;XU Jin-feng;YAN Qi-dong;WANG Ying-zhan(School of Materials Science and Engineering,Xi'an University of Technology,Xi'an 710048,Shaanxi,China;Yuzhou Henglilai Alloy Co.,Ltd.,Yuzhou 461600,Henan,China)

机构地区：[1]西安理工大学材料科学与工程学院,陕西西安710048 [2]禹州市恒利来合金有限责任公司,河南禹州461600

出　　处：《铸造》2020年第8期808-815,共8页Foundry

摘　　要：借助SEM和TEM探索了不同等温淬火温度下等温淬火球墨铸铁(ADI)基体组织的精细结构特征。结果表明,当等温淬火温度为280℃、330℃和380℃时,对应的ADI基体组织分别由奥铁体、奥铁体+条状奥氏体、奥铁体+条状奥氏体+块状奥氏体组成。随着等温淬火温度的升高,奥铁体组织发生粗化,块状高碳奥氏体数量增多,且在奥氏体化温度为920℃时,铁素体针随着奥氏体化保温时间的延长而增长。同时,在普通光镜下观察到的奥铁体组织实则由位向大体平行或位向角约呈20°~25°的高碳奥氏体片和铁素体片交错组成,且在较低温度下等温转变得到的ADI基体中存在有一簇簇由位向大体平行的纳米级高碳奥氏体薄片和纳米级铁素体薄片相互交错组成的极细奥铁体组织,其数量随着等温转变温度的降低而增多,在纳米级高碳奥氏体薄片/针状铁素体薄片晶界处未有碳化物的生成,并且在相邻两簇极细奥铁体之间又夹含有位向角约呈20°~25°的奥铁体组织。此外,在ADI基体组织中的铁素体薄片两侧的奥氏体中碳含量较高,且在沿垂直于铁素体针生长方向上,奥氏体中碳含量随离开铁素体/奥氏体晶界距离的增大逐渐减小,而在块状奥氏体内部,碳含量则呈“U”型分布。The fine structure characteristics of ADI matrix at different austempering temperatures were investigated by means of SEM and TEM. The results show that when the austempering temperature is 280 ℃, 330 ℃ and 380 ℃, the ADI matrix is composed of ausferrite, ausferrite + strip austenite and ausferrite + striped austenite + bulk austenite, respectively, and the ausferritic structure in the matrix is coarsened and the number of bulk high-carbon austenite increases with an increase in austempering temperature. Furthermore, when the austenitization temperature is 920 ℃, the ferritic needle increases with the extension of the austenitization holding time. At the same time, the bundle of ausferritic structure observed under ordinary light microscope is actually composed of high-carbon austenitic slices and ferrite’s slices interleaved, which are roughly parallel to each other in position or with a position angle of about 20°-25°. There are clusters of superfine ausferritic structure with about 1 μm thickness in the matrix of ADI under the isothermal transformation at lower temperature, which is composed of nano-sized high-carbon austenitic slices and nano-sized ferrite’s slices interleaved that are roughly parallel in orientation. The number of superfine ausferritic structure increases with decreasing isothermal transition temperature. No carbides were generated at the grain boundary of nanosized high-carbon austenitic slices/ferrite’s slices. Between the two adjacent clusters of superfine ausferritic structures, there is an inclusion of ausferritic structure with a direction angle of about 20°-25°. In addition, the carbon content of austenite on both sides of ferrite sheet in ADI matrix is higher. And along the direction of vertical ferrite needle growth, the carbon content in the austenite gradually decreases as the distance from ferrite/austenite grain boundary increases. Whereas in the bulk austenite, the carbon content is in the "U" type distribution.

关 键 词：等温淬火球墨铸铁 等温淬火温度 奥铁体 铁素体薄片 奥氏体薄片 

分 类 号：TG250[金属学及工艺—铸造]