【摘要】 利用透射电镜和X射线能谱研究了Nb-V-Ti微合金X70针状铁素体管线钢中析出物的形貌、结构和化学成分。观测结果表明所研究钢中的析出物可分为两大类:一类为高温析出的尺寸较大的复合析出物,尺寸较大的方形TiN粒子为复合析出物的核心,而含Nb的尺寸较小的析出物附着在其一侧或多个侧面生长。在较低温度下,Nb的碳化物和(或)碳氮化物在位错和亚界面上非均匀形核析出,尺寸较小,外貌呈球形。根据钢的化学成分、热力学和X射线能谱分析认为,NbC粒子是本工艺条件下所研究的Nb-V-Ti微合金X70针状铁素体管线钢中的主要析出相。更多还原

【Abstract】 The morphology,structure and chemical composition of precipitates in the final microstructure of Nb-V-Ti microalloyed X70 acicular ferrite pipeline steel were investigated by using Transmission Electron Microscopy(TEM) and Energy Dispersive x-ray Spectroscopy(EDS).Precipitates observed by TEM can be made into two groups.The large precipitates are complex compounds that comprise TiN precipitate of square shape as core with fine Nb containing precipitate nucleated on pre-existing TiN precipitate as caps on one or more faces at high temperature.In contrast,the fine and spherical Nb carbides and/or carbonitrides precipitate heterogeneously on dislocations and sub-boundaries at low temperature.From analysis in terms of thermodynamics,EDS and chemical composition of the steel,NbC precipitation is considered to be the charging precipitation behavior in the tested steel under the processing conditions of this research.更多还原