超低碳钢在铁素体生长过程中硼分布的变化

通过对照显微结构与硼的自射线径迹显微照相（ＰＴＡ），研究了一种超低碳含硼钢在铁素体生长过程中硼分布的变化，发现：在发生等温铁素体相变前，硼已偏聚在奥氏体晶界上；铁素体在奥氏体晶界形核；在有铁素体生成的奥氏体晶界上，硼偏聚减弱；沿晶界长出的小块铁素体中硼浓度明显高于奥氏体，但随铁素体长大，其硼含量逐渐与母相持平。这些现象表明，铁素体长大不受硼在奥氏体中扩散的控制

Variation of Boron Distribution during the Growth of Ferrite in Ultra-Low Carbon Steel

By contrasting microstructure with boron distribution (PTA) in the same area of samples, variation of boron distribution during the growth of ferrite in ultra-low carbon steel has been investigated. It is found that boron atoms segregate at original austenitic grain boundaries before ferritic transformation starts during isothermal holding. The ferrite nucleates at austenitic grain boundaries, which leads to the decrease of boron segregation at the boundaries. The density of boron in small pieces of ferrite along austenitic boundaries may be much higher than that in austenitic matrix,but it will decrease gradually and homogenize as the ferrite grows. The results indicate that the growth of ferrite is not controlled by diffusion of boron in austenite.