Texture development during multi-step cross rolling of a β titanium alloy: Experiments and simulations

Abstract

In the present work, microstructure and texture evolution during multi-step cross rolling of a β-Ti alloy was investigated. The as-received samples were cross rolled in a laboratory rolling mill to 20%, 40%, 60% and 80% thickness reduction. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the changes in microstructure, while the changes in bulk texture were evaluated using X-ray diffraction. The as-received sample consisted of equiaxed as well as elongated grains. Equivalent circle average grain size (AGS) and the average band thickness (ABT) along normal direction (ND) for as-received β-Ti sample was 50 ± 3 μm and 27 ± 1.8 μm respectively. The AGS and ABT decreased with increase in cold rolling reduction (for 80% cold rolled sample ABT was 7.5 ± 2.3 μm). Another important feature was the presence of strain localizations in the cold rolled samples, the frequency of which increased with increase in strain. The as-received sample showed the presence of α (rolling direction RD//<110>) and γ (ND//<111>) fibers. At highest strain (80% cold rolling), rotated cube ({100}<110>) component was found to be significantly stronger than the γ-fiber texture. Visco-Plastic Self Consistent (VPSC) model was used for the simulation of texture during cold cross rolling. Qualitatively, full constraint VPSC model was found to match reasonably well with the experimental data. α-Fiber, γ-fiber and rotated cube were over estimated in the VPSC texture predictions.