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采用碳萃取复型技术和采用透射电镜TEM+EDX技术研究分析汽车用超细晶亚稳钢热轧板和两相区不同退火时间钢板中析出物的尺寸、形态、分布和成分组成。结果表明:热轧板中主要析出物为类似正方形TiN、椭圆状NbTi(CN)和细小圆球状NbC,TiN析出于浇铸过程,在轧制冷却过程中,Nb、C元素以TiN粒子为形核点析出的复杂析出相NbTi(CN),NbC析出于位错与亚晶界处;在两相区退火过程中,部分碳化物固溶于奥氏体中,未固溶的析出物相互吞并粗化,为典型的Oswald熟化机制;在两相区退火初期,有矩形TiN析出物析出,随着退火时间的延长,析出物形貌向圆形和椭圆形发展,进一步粗化,保温6 h以后,析出物为NbTi(CN)和NbC,未发现TiN析出物。
The size, morphology, distribution and composition of the precipitates in the ultra-fine grained metastable steel hot-rolled plates and the two-phase annealed steel plates were investigated by TEM and EDX TEM. The results show that the main precipitates in the hot-rolled sheet are TiN, elliptic NbTi (CN) and fine spherical NbC. TiN precipitates in the casting process. During rolling and cooling, the Nb and C elements take the form of TiN particles The complex precipitates NbTi (CN) and NbC are precipitated in the dislocation and subgrain boundaries. During the annealing in the two-phase region, some carbides dissolve in the austenite and the undissolved precipitates swallow each other roughly , Which is a typical Oswald ripening mechanism. At the initial stage of annealing in the two-phase region, a precipitated rectangular TiN precipitate. With the extension of annealing time, the morphology of precipitates evolves round and oval, further roughening and holding for 6 h , Precipitates NbTi (CN) and NbC, TiN precipitates were not found.