中文摘要：

控制钢中第二相粒子（包括非金属夹杂物和碳氮化物）的形貌对降低非金属夹杂物的危害、提高钢材力学性能等具有重要作用。本工作通过引入Jackson α指数建立了钢中第二相粒子形貌的预测理论模型，指出钢中第二相粒子形貌由其熔化熵、生长方向和温度（过冷度）决定。通过非水溶液电解的方法和室温有机溶液包埋（RTO）技术，结合SEM分析了4个钢种各类夹杂物的三维形貌以及其内部特征，实测的第二相粒子形貌与理论预测一致。理论和实验观察结果均证明，当第二相粒子Jackson α指数大于3时，其形貌为小面状；Jackson α指数小于2时，呈非小面状。

英文摘要：

It is significant to reduce the negative effects of non-metallic inclusion on steel and to improve steel mechanical properties through controlling the morphology of the secondary phase particle including non-metallic inclusion, nitride and carbide. Compared with particles with irregular shape, globular second phase particle could reduce the stress concentration during rolling and heat treatment process obviously and lower its harmfulness to steel toughness. A theoretical model to predict the morphology of the secondary phase particle in steel has been established by introducing a dimensionless Jackson a factor, and the morphology of the secondary phase particle is determined by its dissolved entropy, growth direction and temperature or undercooling. Non-aqueous solution electrolysis extraction and room temperature organic （RTO） technique were applied to detect the 3D morphology of the secondary phase particle and its inner morphology combining with SEM. The morphologies of particles observed in four different types of steels are in good agreement with the theoretical predictions. Theoretical predictions and experimental observation were both confirmed that the secondary phase particle is faceted in morphology when its Jackson a factor is more than 3 and non-faceted when its Jackson a factor less than 2.