Fracture behavior of twinning-induced plasticity steel during wire drawing

Abstract

The present study focuses on the effects of strain and temperature distribution on the fracture behavior in twinning-induced plasticity (TWIP) steel during wire drawing in order to understand the fracture mechanism of drawn TWIP steel wire. The deformation and fracture behaviors of a wire subjected to the reduction of area (RA) per pass of 10% (lower reduction, LR) and 20% (higher reduction, HR) were analyzed. The deformation temperature of the wire had a linear relationship with RA per pass during wire drawing, which means that the HR wire exhibited higher temperature compared to the LR wire. The maximum effective and shear strains occurred at the near surface area, i.e., at the relative distance of 0.9 from center to surface of the wire, leading to the maximum twinning rate and geometrically necessary dislocation density at the near surface area. Also, the near surface area had a lower temperature than that of the surface area. Therefore, cracks were initiated at the near surface area in TWIP steel during wire drawing, which was well observed from the fractography by scanning electron microscopy. The HR wire had a higher drawability compared to that of the LR wire because the HR wire had a lower twinning rate at the near surface area due to the higher stacking fault energy and the lower effective and shear strains. This unique fracture phenomenon of drawn wire is presented for the first time in this study since it rarely occurs in general metals during wire drawing.