The silicide precipitation mechanism and spheroidization behavior of αp phase in a novel near-β titanium alloy during isothermal multi-directional forging process

The tread-off between the strength and ductility of near-beta titanium alloys has significantly limited their applications. In this study, a novel near-beta titanium alloy containing Si element was designed, and the influence of alpha-phase spheroidization and silicide precipitation on the mechanical properties was investigated during isothermal multi-directional forging (IMDF) process. The results showed that the beta grain is easy to deform and elongate, and the deformed alloy mainly undergoes dynamic recovery (DRV) rather than dynamic recrystallization (DRX). Some silicides are dissolved due to the temperature rise caused by IMDF and the diffusion of atoms on the top of the irregularly shaped silicides. Zr and Si elements are redistributed and segregated at the dislocation, resulting in the formation of submicron-scale and nano-scale silicides. Lath-like alpha p phase will precipitate from the prior beta grain after heat treatment in the dual-phase region, and the volume fraction of alpha p phase increases with the decrease of heat treatment temperature. In addition, rotation deformation and spheroidization of the lath-like alpha p phase occur during multi-pass IMDF in the dual-phase region. When multi-pass IMDF temperature is 770 degrees C, the silicide distribution is uniform, and the alpha p phases are equiaxed, which is conducive to the improvement of ductility. The obtained results provide a new way to prepare the Si-containing near-beta titanium alloys with excellent mechanical properties.