Silicide precipitation behavior and dynamic recrystallization mechanism of a novel titanium alloy with widmanstatten microstructure

Abstract

Focusing on a new silicon-rich α+β Ti alloy with widmanstatten microstructure, the precipitation behavior of silicides and the dynamic recrystallization (DRX) mechanism during hot deformation were systematically investigated by thermal simulation compression tests. The Arrhenius constitutive model for the high-temperature deformation of the Ti-5Al-7.5V-0.5Mo-0.5Zr-0.5Si alloy was established, indicating that the DRX is the main softening mechanism. Combined with microstructure characterization, it was found that there is a certain competitive relationship between silicides precipitation and DRX, resulting in a non-monotonic change in the silicides precipitation. With the increasing temperature, the size of silicides increases, while the volume fraction first increases and then decreases. As the strain rate decreases, the size of silicides first decreases and then increases, while the volume fraction continues to decrease. The DRX fraction increases significantly at 890 ​°C/0.001 s⁻¹. Additionally, the fragmentation and spheroidization of the α phase are achieved through the continuous dynamic recrystallization (CDRX). Furthermore, by integrating the dynamic material model and the relevant parameters the DRX & silicide precipitation, a novel multi-dimensional hot working map was constructed. The optimal hot processing parameters were determined as 870–884 ​°C/0.004–0.015 s⁻¹, where the high-power dissipation factor η, the appropriate DRX volume fraction, and the great strengthening effect of silicides can be readily obtained, which contributed effectively to the effectively balance between the strength and plasticity of this silicon-rich Ti alloy. The investigation provides an important theoretical basis for optimizing the hot working process of silicon-rich Ti alloys and promoting the industrial application.