Deformation Features of the Propagation of Cleavage Cracks in a Ferritic-Pearlite Microstructure in the Ductile to Brittle Transition Interval.

In the paper, the deformation features of the propagation of cleavage cracks in low-alloy low-carbon steel with a ferritic-pearlite microstructure by example of steel 09G2S after hot rolling are investigated. The studied cleavage cracks were obtained in impact bending tests at temperatures in the ductile to brittle transition interval. The study was carried out by transmission electron microscopy, transmission Kikuchi diffraction, and electron backscattered diffraction. It is shown that the deformation accompanying the growth of the cleavage crack in the ferritic-pearlite microstructure is formed when the joints between the cracks propagating in parallel planes break. The crack growth within a single plane occurs without any recorded deformation. The joints are broken by a ductile mechanism according to the scheme of mixed loading by opening and shear. Overlapping of the cleavage cracks determines the relationship between the shear mode and the opening mode during joint deformation, which controls the shape and depth of the plastic deformation zones. [ABSTRACT FROM AUTHOR]