Fatigue damage evolution in ultrafine-grained interstitial-free steel

Abstract

The current work presents the crack propagation behavior in ultrafine-grained (UFG) interstitial-free (IF) steel, and in particular, focuses on the damage evolution in UFG IF steel under cyclic loading. The current results indicate that equal-channel angular pressing (ECAP) has a major influence on the cyclic deformation response of the UFG IF steel, such that the failure and the crack path depend on the inclination plane during ECAP. Furthermore, the UFG IF steel demonstrates significant notch sensitivity in comparison to its coarse-grained counterpart. This is attributed to the ultrafine grains with a large volume fraction of high-angle grain boundaries, where glide of dislocations is hindered and the resulting internal stresses increase the stress concentration further in the presence of a pre-existing notch.