LAUSR

Abstract The present work investigates the crack propagation behaviour in a twinning-induced plasticity (TWIP) steel. At room temperature, the dominant fracture mechanism of TWIP steel is quasi-cleavage, which is assisted by the deformation twins since such fracture mode is circumvented at 573 K as deformation twins are prohibited. The quasi-cleavage fracture mechanism is responsible for the high notch sensitivity and low essential work of fracture (EWF) of TWIP steel at room temperature. Furthermore, the crack propagation process of TWIP steel at 298 K has been characterized quantitatively by in-situ digital image correlation (DIC) technique and J resistance curve (J-R curve). The results show that the cracking process of TWIP steel at 298 K is stable, even though cleavage patches are observed on the fracture surface. A physical model based on the dislocation behaviour at the crack tip has been proposed to explain qualitatively the mechanism responsible for the stable cleavage cracking in TWIP steels.