Microstructural analysis on cleavage fracture in pearlitic steels

Microstructural features controlling cleavage fracture in pearlitic structures were investigated by means of scanning electron microscopy and electron backscattered diffraction. It was found that pearlite block size corresponds well to the cleavage facet size, and a single cleavage facet usually contains multiple pearlite colonies. Pearlite block size and cleavage facet size decrease with the refinement of prior austenite grain size, while pearlite colony size only changes slightly. The cleavage crack can largely deflect at block boundaries rather than at colony boundaries. Pearlite block can act as the dominant substructure on cleavage crack propagation in pearlitic steels. - Highlights: •The cleavage crack propagation path in pearlitic structures was analyzed by EBSD. •Pearlite block boundaries can effectively hinder the crack propagation. •Pearlite block size corresponds well to the cleavage facet size. •A single cleavage facet usually contains multiple pearlite colonies.