The Role of Notches on Fatigue Life of TWIP Steel in the HCF Regime

Abstract

The present paper reports on the fatigue response of a commercial high manganese steel that features the twinning-induced plasticity (TWIP) effect in the high-cycle fatigue (HCF) regime. Specifically, attention was paid to the influence of the degree of pre-deformation and notches on the damage initiation and propagation in the TWIP steel studied. As monotonic pre-deformation significantly increases the fraction of twins and concomitant the strength of the steel, the fatigue properties and notch sensitivity are altered drastically. A thorough experimental approach including mechanical testing and microstructural characterization was employed to shed light on the microstructure-mechanical properties-relationships in order to deepen the understanding of the critical damage mechanisms. The current study clearly lays out that competing mechanisms effect the fatigue response of the TWIP steel, i.e. pre-deformation leads to strengthening but also induces damage. Since both effects evolve differently upon pre-deformation, fatigue performance can be optimized by appropriate amounts of pre-deformation.