Deformation structure around a crack in γ′-Fe4N layer of nitrided extra-low-carbon steel subjected to cyclic tensile test

Abstract

Numerous slip bands were detected in the γ′ layer of nitrided steel subjected to cyclic tensile testing, indicating that γ′ can easily deform plastically under a low-applied stress (175 MPa). A crack arrested inside a γ′ grain propagated along the {100} and {111} planes, and planar dislocations were emitted from the crack tip. The stress concentration at the crack tip induced a cleavage fracture and slipping-off in the γ′, leading to a crack propagation.