Texture and dislocation structures observation in a dual-phase steel under strain-path changes at large deformation

Abstract

The aim of the present work is to analyse the evolution of the microstructure of a dual-phase steel in term of dislocation organization under two-stage strain-path changes sequences in connection with the crystallographic grain orientation in order to achieve a more comprehensive explanation of the anisotropic behaviour under complex strain-path changes for these steels at room temperature. The mechanical tests are performed using sequences of simple shear tests and/or uniaxial tensile tests with three different strain-path changes, namely monotonic, Bauschinger and orthogonal loading. After monotonic deformation, well-defined dislocation walls are developed whose orientation depends on the grain orientation. After a Bauschinger strain-path change, a partial dissolution of the preformed dislocation sheets is observed whereas after an orthogonal strain-path change they remain in most grains. However, their number and their orientations become more and more compatible with the last deformation mode, with strain increase.