Torsion textures produced by deformation and by dynamic recrystallization in a-iron and two IF steels

The textures of two IF steels and a high purity $ alpha$-iron were determined after deformation in torsion over the temperature range 20-840$ sp circ$C. The three characteristic bcc torsion fibres are described in detail and the locations of some important ideal orientations are identified on the $ {110 }$ pole figure. At room temperature, these are the F(110)(001), J1 (011) (211), J2 (110) (112), D1 (112) (111), D2 (112) (111), E1 (011) (111) and E2 (011) (111). At elevated temperatures, the conditions were chosen so that dynamic recrystallization (DRX) took place in the ferrite and that static recrystallization was avoided during cooling after deformation. The DRX textures differ from those observed at room temperature and are dominated by the D2 (112) (111), D1 (112) (111) and E2 (011) (111) components. The D2 becomes increasingly important as the strain is increased, which leads to weakening of the D1 and disappearance of the E2 at large strains.Deformation textures were simulated using the rate sensitive theory of crystal plasticity. These called for lengthening to take place, in agreement with the measured length changes. The simulated and experimentally observed 'tilt' phenomena are similar to those commonly reported in the literature for fcc materials. The explanation of this phenomenon developed for the latter materials is extended to bcc metals. The development of torsion textures is discussed in terms of the rotation rate vector R, the divergence-convergence properties of orientation flow, and the stability parameter S.DRX textures were simulated using a model based on sequential deformation, nucleation and growth steps. The types of oriented nucleation and selective growth required to reproduce the experimentally observed textures are discussed. The simulations indicate that the low energy nucleation mechanism plays a dominant role in the formation of bcc DRX textures. The results are also interpreted in terms of the continuous (in situ) and discontinuous mechanisms of dynamic recrystallization