摘要:
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。
Abstract:
The size,morphology,distribution and components of precipitates in hot rolled ultrafine grained metastable automobile steel under hot rolling and intercritical annealing after different holding time were systematically investigated by using carbon extraction replica,transmission electron microscopy (TEM) and energy dispersive X-ray spectrometry (EDX).The results show that the precipitates are mainly composed of TiN,NbTi(CN) and NbC after hot rolling.The TiN precipitates during casting process,NbTi(CN) precipitates on the existing TiN particles and NbC precipitates in dislocations and sub-boundaries during hot rolling process.During intercritical annealing process,part of carbides dissolves into austenite,and remained precipitates merges with each other and coarsens according to typical Oswald ripening mechanism.In the course of initial annealing,some rectanular TiN precipitates from the matrix.With the increase of annealing time,the morphology of precipitates develop into circular and oval.After holding for 6hs,the precipitates are mainly composed of NbTi(CN) and NbC,the TiN is not found.
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