A comparative analysis of a unique DRX process in achieving a homogeneous distribution of β grains in the single phase region of as-cast Ti644321 alloy

Abstract

This study aims to investigate the distinctive characteristics of a specialized dynamic recrystallization (DRX) process, which results in a fine and uniform distribution of β grains within the single phase region of as-cast Ti644321 alloy. The formation of deformation bands (DB) and flow localization (FL) is a result of the instability region. On the other hand, the stability region exhibits significant dynamic recrystallization (DRX). The phenomenon of DRX encompasses continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX), and the coupling mechanism of DDRX and CDRX, which was discovered in this study. The occurrence of DDRX is attributed to grain boundary bulging, while CDRX is a result of the progressive rotation of subgrains. A strain rate of 0.1 s−1 was found to form a fine and uniform distribution of β grains. The formation of this microstructure is facilitated by a coupling mechanism that combines CDRX and DDRX, which involves the grain boundary strain concentration effect that triggers DDRX and the subgrain rotational nucleation process of CDRX. The deformation mechanism of the alloy during hot deformation varies depending on the η value. In the high η region, the primary deformation mechanism is mainly DDRX+CDRX, while in the medium η region, it transitions to CDRX+DRV. Ultimately, in the low η region, the primary deformation mechanism is DB + FL. The presence of a high proportion of DBs hinders DRX. This study provides novel insights into the mechanisms of DRX in β titanium alloys and emphasizes the significance of considering different forms of DRX.