Texture development in cold rolled and annealed C-Mn-Siand C-Mn-Al-SiTRIPsteels

The texture of two transformation induced plasticity steels has been studied by means of crystallographic orientation mapping. Texture measurements were carried out on ferrite, bainite, and austenite. The polygonal ferrite and the bainite texture, both bee, could be distinguished based on the image quality parameter of the electron backscattering diffraction measurement. Both bee textures were very similar, the main difference being the more pronounced < 111 > (alpha) \ \ ND (ND=normal direction) and < 110 > (alpha) \ \ RD (RD=rolling direction) fibre textures in the polygonal ferrite. The fee texture was a strong gamma deformation texture, characterised by the beta fibre. The presence of the alpha fibre confirmed the strong < 110 > (gamma) \ \ ND direction, which was previously detected by means of X ray diffraction (XRD). The measured fee and bee textures were used to calculate orientation distribution function transformations according the Bain, Kurdjumov-Sachs, and Nishiyama-Wasserman orientation relationships. The predicted cube component {001}(gamma) < 100 > (gamma), which was missing in the measured texture, of gamma (ret) indicates a variant selection for the gamma --> alpha (B) transformation. In addition it was shown that crystallographic orientation mapping could be used to make reliable phase fraction determinations, which were previously based on the light optical microscopy of colour etched specimens. This also proves that XRD determination of gamma (ret) is flawed owing to the strong texturing of all phases present in the microstructure.