Microstructure Study on Large-Sized Ti–6Al–4V Bar Three-High Skew Rolling Based on Cellular Automaton Model

Abstract

The large diameter titanium alloy bars are usually manufactured by forging, which leads to large metal loss, high cost, low efficiency and limited product specifications. This paper adopted three-high skew rolling technology to roll Ti–6Al–4V bar with the diameter of 300 mm. With the reduction of 50 mm, the three-roll skew rolling model was developed by DEFORM-3D finite element software. A cellular automatic model (CA model) of large-sized titanium alloy bar cross-rolled was established, considering the effects of dislocation, recovery and nucleation on dynamic recrystallization. The microstructure evolution process is effectively simulated. During the process of rolling, dynamic recrystallization occurs in the outer layer of the rolled piece at first. The new nucleations form at the grain boundary, then grow into their secondary phase. With the rolling proceeding, the dynamic recrystallization gradually extends to the core of bar. The microstructure of the rolled bar is uniform and the grain size is refined with the average grain size of approximately 10 μm. The simulation results are compared with the experimental results, the actual grain size is a little coarser than that obtained by the CA model. Some reasons are given to reasonably explain the phenomenon.