Li Zhaosen, Ge Jinyang, Kong Bin, Luo Deng, Wang Zhen, Zhang Xiaoyong
State Key Laboratory of Powder Metallurgy, Central South University, Lu Mountain South Road, Changsha 410083, China.
Hunan Xiangtou Goldsky Titanium Metal Co. Ltd., No. 116, Linyu Road, Yuelu Zone, Changsha 410221, China.
Materials (Basel). 2023 Jan 29;16(3):1140. doi: 10.3390/ma16031140.
In this paper, the dependence of dynamic recrystallization (DRX) and post-dynamic recrystallization (PDRX) of TC18 alloy on strain rate within the range of 0.001 s~1 s was investigated through isothermal compression and subsequent annealing in the single-phase region. Electron backscatter diffraction (EBSD) characterization was employed to quantify microstructure evolution and to reveal the recrystallization mechanism. At the thermo-deformation stage, the DRX fraction does not exceed 10% at different strain rates, due to the high stacking fault energy of the β phase. During the subsequent annealing process, the total recrystallization fraction increases from 10.5% to 79.6% with the strain rate increasing from 0.001 s to 1 s. The variations in the geometrically necessary dislocation (GND) density before and after annealing exhibit a significant discrepancy with the increasing strain rate, indicating that the GND density is a key factor affecting the PDRX rate. The PDRX mechanisms, namely meta-dynamic recrystallization (MDRX), continuous static recrystallization (CSRX) and discontinuous static recrystallization (DSRX), were also revealed during the annealing process. A new kinetic model coupling DRX and PDRX was proposed to further describe the correlation between recrystallization and the strain rate during continuous deformation and annealing. This new model facilitates the prediction of recrystallization fraction during isothermal deformation and annealing of titanium alloys.
本文通过在单相区进行等温压缩及后续退火，研究了TC18合金在0.001 s~1 s应变速率范围内动态再结晶（DRX）和动态再结晶后（PDRX）对应变速率的依赖性。采用电子背散射衍射（EBSD）表征来量化微观组织演变并揭示再结晶机制。在热变形阶段，由于β相的层错能较高，不同应变速率下的DRX分数均不超过10%。在随后的退火过程中，随着应变速率从0.001 s增加到1 s，总再结晶分数从10.5%增加到79.6%。退火前后几何必需位错（GND）密度的变化随应变速率增加呈现出显著差异，表明GND密度是影响PDRX速率的关键因素。在退火过程中还揭示了PDRX机制，即亚动态再结晶（MDRX）、连续静态再结晶（CSRX）和不连续静态再结晶（DSRX）。提出了一种耦合DRX和PDRX的新动力学模型，以进一步描述连续变形和退火过程中再结晶与应变速率之间的相关性。该新模型有助于预测钛合金等温变形和退火过程中的再结晶分数。
