The effect of strain path change on texture evolution at finite strain of multiphase steel: numerical and experimental investigations

Two-stage sequences of simple shear and/or uniaxial tensile tests conducted on TRIP800 steel sheet and supplemented by texture measurements are reported. The purpose is a better understanding of the macroscopic work-hardening behaviour and its microstructural origin. According to the previously published work on single phase ferrite steel; the peculiar macroscopic transient effect in flow stress was mainly associated to the microstructural destabilization (e.g. reinforcement, dissolution or rearrangement of the previously formed dislocation walls). In addition, the macroscopic work-softening observed at the beginning of the second stage of cross-loading was attributed to the micro-band occurrence. Considering the actual multiphase steel, the main difference lies in the absence of the peculiar transient effect in flow stress upon cross-loading (where no macroscopic work-softening is observed) and the associated microstructural mechanisms (no formation of micro-bands). Besides, the initial texture for the actual multiphase steel is in some extent different to the previously investigated single phase steel mainly made up of the gamma-fibre. Therefore, a detailed analysis of the measured deformed textures is carried out in order to investigate the contribution of the texture evolution on the macroscopic work-hardening. The computations of the orientation stability map as well as the predicted texture evolutions using the classical full constraint Taylor-Bishop-Hill (TBH) model are performed for a better understanding of the observed texture development. The influence of the texture evolution on the shape of the stress-strain curves, as well as on the remaining symmetries of the material, is also discussed. Explicitly, we show that despite the presence of a well developed texture in the as-received and deformed material, the contribution of the geometrical hardening (i.e. textural evolution) on the macroscopic behaviour remains small compared to the microstructural one.