Study of Plastic Heterogeneity in a Low Carbon Steel Sheet by EBSD

Abstract

The aim of this study is to analyze the development of plastic heterogeneity in low carbon steel sheets when they are subjected to different loading paths, typical of forming process operations. Nakajima type tests are performed and employed to determine the Forming Limit Curve. This study attempts to characterize, at polycrystalline level, the plastic heterogeneity and its gradients, enabling the definition of correlations between the dislocation structure, grain size and crystallographic orientations. Geometrically Necessary Dislocations (GND) is estimated by calculating the curvature tensor from the measured orientation field. The results are compared with the Kernel Average Misorientation factor (KAM), normally available in the TSL- OIM EBSD software. The Quantification of the distribution of disorientations in each grain is performed by evaluating the secondorder central moment of crystal misorientations (Q tensor). Finally, the evaluation of the isotropic and anisotropic factors of the Q tensor and the distribution of the misorientation preferential axes allow characterizing the microstructure dependent on the applied loading, the grain size or the crystal orientation.