Texture development during the torsion testing of α-iron and two IF steels

Abstract

The textures of two interstitial free (IF) steels and a high purity α-iron were determined after deformation in torsion over the temperature range 20–500°C. The three characteristic b.c.c. 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 (0 1 ̄ 1) [ 2 ̄ 11], J2 (1 1 ̄ 0) [ 1 ̄ 1 ̄ 2], D1 (11 2 ̄ ) [111], D2 ( 1 ̄ 1 ̄ 2) [111], E1 (01 1 ̄ ) [111] and E2 (0 1 ̄ 1) [111]. The D1, D2 and F dominate, while the E1 and E2 appear at slightly lower intensities at 400 and 500°C. Texture simulations were carried out 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 f.c.c. materials. The explanation for this phenomenon developed for the latter materials is extended to b.c.c. metals. The development of torsion textures is discussed in terms of the rotation rate vector Ṙ, the divergence-convergence properties of orientation flow and the stability parameter S.