In‐situ microscopic analysis of ferritic ductile iron during tensile loading: Relation between matrix heterogeneities and damage mechanisms

Abstract

An in‐situ microscopic analysis of the damage mechanisms of ferritic ductile iron under uniaxial tensile testing is carried out in this work. The experimental methodology combines specialized metallography techniques, in‐situ optical microscopy observation during loading, and digital image correlation analysis to obtain the strain values at the microscopic level. The results show that the crack initiation is preferentially located at matrix‐nodule interface and ferritic grain boundaries. The propagation of multiple cracks across the internodular ligaments that later coalesce into a single dominant crack is responsible for the final fracture. Noticeably, despite the heterogeneous nature of the Last‐to‐Freeze zones, the cracks propagate avoiding these microsegregated areas. The results provide new insights for the better understanding of the influence of ferritic ductile iron heterogeneities on the fracture process for quasistatic uniaxial loading.