Multiphase bainitic steels, as a third generation of advanced high strength steels, show promising properties for automotive applications. Understanding the micro-mechanisms of damage initiation during plastic deformation is a key to further mechanical properties enhancement. The topological effect of martensite as a second phase constituent on local damage nucleation activity is significant. This effect has been studied in two different martensite banded microstructures produced by two various annealing cycles. The postmortem damage analysis by a scanning electron microscope on uniaxial loaded samples, revealed more damage nucleation along the dispersed and fragmented martensite phase within martensite banded regions. More pronounced strain partitioning was observed in coarse bainitic grains between adjacent martensite blocks. It is shown that the fracture strain is not controlled by local damage activities, implying that earlier damage initiation or an increased volume fraction of voids does not give rise to a reduced ductility.

多相贝氏体钢作为第三代高级高强度钢，在汽车应用中显示出令人鼓舞的性能。了解塑性变形过程中损伤引发的微观机制是进一步提高机械性能的关键。作为第二相成分的马氏体对局部损伤成核活性的拓扑作用是显着的。已经在由两个不同的退火循环产生的两个不同的马氏体带状微观结构中研究了这种效果。通过扫描电子显微镜对单轴加载样品进行的事后破坏分析显示，在马氏体带状区域内，沿着分散和破碎的马氏体相的破坏核更多。在相邻马氏体块之间的粗贝氏体晶粒中观察到更明显的应变分配。