次生针状铁素体激发形核行为研究

Study on Induced Nucleation Behavior of Secondary Acicular Ferrite

氧化物冶金研究过程中的晶内针状铁素体是一种能够有效细化晶粒、提高钢综合性能的优良组织。本工作借助金相显微镜、扫描电镜和透射电镜对初生针状铁素体激发形核所形成的次生针状铁素体进行组织、微结构以及形核机理分析研究。结果表明:初生针状铁素体激发形核所形成的次生针状铁素体,为非共格结构,属于边-面型形核模型。次生铁素体的形成与诱发初生针状铁素体形核的夹杂物成分、激发形核位置以及冷却速度有关。起初形核点为切变转变,此类转变是由碳原子集体有规则的近程迁移,进而瞬间降低系统能量完成的。随后为界面控制的扩散转变,碳原子在初生与次生针状铁素体的晶界处扩散迁移,通过碳元素溶质富集和不连续扩散降低形核能,完成形核过程。

In the process of oxide metallurgy,intragranular acicular ferrite is an excellent structure that can effectively refine grains and improve the overall performance of steel.In this work,throuth metallographic microscope,scanning electron microscope and transmission electron microscope,the organization,microstructure and nucleation mechanism of secondary acicular ferrite,which was formed by the nucleation of primary ferrite induced by inclusions,were analyzed and studied.The results show that the primary acicular ferrite stimulates nucleation and the secondary acicular ferrite is a non-coherent structure and belongs to the edge-to-face nucleation model.The formation of secondary ferrite is related to the composition of inclusions that induce nucleation of primary acicular ferrite,the location of excited nucleation and the cooling rate.Initially,the nucleation point is a shear transformation,and the regular short-range migration of carbon atoms collectively reduces the system energy instantly.Followed by the interface-controlled diffusion transition,carbon atoms diffuse and migrate at the grain boundary between the primary and secondary acicular ferrite,then the nucleation energy is reduced through carbon solute enrichment and discontinuous diffusion,and finally the nucleation process is completed.