The effect of microstructural banding on failure initiation of HY-100 steel

Microstructural banding of a hot-rolled HY-100 steel plate was accentuated by cooling slowly from the austenite region, which resulted in alternating layers of soft, equiaxed ferrite, and hard "granular ferrite." The segregat ion of substitutional alloying elements such as Ni and Cr was identified as the main cause for the microstructural banding. Such banding induces aniso tropic flow behavior at large strains, with deformation constrained by "pan cake-shaped" bands of the hard granular ferrite. Tensile tests of circumfer entially notched HY-100 specimens were performed in order to explore the st ress dependence of failure in the slow-cooled as well as the quenched and t empered conditions. The failure behavior of the slow-cooled, microstructura lly banded material exhibited a pronounced susceptibility to a void-sheet m ode of failure. However, the absence of carbides within the equiaxed ferrit e delays void coalescence and material failure to higher strains than in a quenched and tempered microstructure, despite the increased susceptibility to shear localization.