The evolution of strain pattern induced by banded structure under uniaxial tension in low-carbon microalloyed steel

The presence of banding inhomogeneities is detrimental to the mechanical behaviors of steels due to the strain anisotropy. In this paper, combined with the in-situ tensile stage, digital image correlation (DIC) method was used to investigate the influence of banding pattern including the size, quantity and morphology on the continuous localized deformation and fracture behavior of low-carbon microalloyed steel under the uniaxial tension load. A zero-deformation test was introduced at the beginning of the experiment, where the accuracy and stability of DIC for this application were validated. The results show that the effect of banded structure on local deformation and damage evolution is significant. Compared to the rolling direction (RD) tensile, the local deformation of banded structure exhibits a higher sensitivity to the transverse direction (TD), and the development of shear bands is clearly affected by the local high strains caused by the deformation of soft banding. The coarse banding (CB) in specimen could decrease the mechanical properties of material. Meanwhile, the mechanical anisotropy is explained by the evolution model of local deformation. This work is helpful to understand the effect of banded structure on the mechanical behavior of steel.