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

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. (c) 2005 Elsevier B.V. All rights reserved.