Annealing textures in cold-rolled duplex type steel

Duplex type austenitic-ferritic steel 00H18N6Mo3 was cold-rolled up to 85% of deformation taking either low or high reductions per pass (variants A and B respectively) and subsequently annealed at the temperatures 800 and 850 degrees C. X-ray investigations included the phase analysis, measurements of pole figures and calculation of the orientation distribution functions (ODF's) For the case of each phase. Textures of ferrite and austenite after rolling and annealing were analysed within the centre layers of the sheets. The analysis included texture simulation by transformation of experimental ODF's according to Kurdjumow-Sachs (K-S) orientation relationship. Characteristic feature of deformation and annealing textures in duplex steel under investigation was their fibrous character in both phases, alpha and gamma. The rolling texture of ferrite in duplex steel was strong in comparison to one-phase steels especially for the case of rolling variant B. Deformation texture of austenite was relatively weak or nearly random, depending on the rolling variant, even after 85% of reduction. It was concluded that development of ferrite rolling texture may be affected by the phase transformation (gamma-->alpha) induced by plastic deformation. During annealing the main changes within the textures of both phases resulted from the transformation of ferrite into austenite (alpha-->gamma) as well as the precipitation of the sigma phase (FeCr). The crystallographic relationship between the textures of both phases is well described by K-S relation. It seems however that not all of the 24 possible orientations are equally probable and some kind of variant selection takes place during deformation, affecting the resulting annealing texture.