Qu Mingjia, Gu Zhengwei, Li Xin, Yi Lingling, Li Yi, Yu Ge, Zhao Yafu
State Key Laboratory of Automobile Materials, Jilin University, Changchun 130025, China.
Department of Materials Science and Engineering, Jilin University, Changchun 130025, China.
Materials (Basel). 2024 May 24;17(11):2531. doi: 10.3390/ma17112531.
Through the study of the thermal rheological behavior of Ti6Al4V alloy at different temperatures (500 °C, 600 °C, 700 °C, and 800 °C) and different strain rates (0.1 s, 0.05 s, 0.01 s, and 0.005 s), a constitutive model was developed for Ti6Al4V alloy across a wide temperature range in the hot stamping process. The model's correlation coefficient reached 0.9847, indicating its high predictive accuracy. Hot processing maps suitable for the hot stamping process of Ti6Al4V alloy were developed, demonstrating the significant impact of the strain rate on the hot formability of Ti6Al4V alloy. At higher strain rates (>0.05 s), the hot processing of Ti6Al4V alloy is less prone to instability. Combining hot processing maps with hot stamping experiments, it was found that the forming quality and thickness uniformity of parts improved significantly with the increase in stamping speed. The phase composition and microstructures of the forming parts under different heating temperature conditions have been investigated using SEM, EBSD, XRD, and TEM, and the maximum heating temperature of hot stamping forming was determined to be 875 °C. The recrystallization mechanism in hot stamping of Ti6Al4V alloys was proposed based on EBSD tests on different sections of a hot stamping formed box-shaped component. With increasing deformation, the effect of dynamic recrystallization (DRX) was enhanced. When the thinning rate reached 15%, DRX surpassed dynamic recovery (DRV) as the dominant softening mechanism. DRX grains at different thinning rates were formed through both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), with CDRX always being the dominant mechanism.
通过研究Ti6Al4V合金在不同温度（500℃、600℃、700℃和800℃）和不同应变速率（0.1s⁻¹、0.05s⁻¹、0.01s⁻¹和0.005s⁻¹）下的热流变行为，建立了Ti6Al4V合金在热冲压过程中宽温度范围内的本构模型。该模型的相关系数达到0.9847，表明其预测精度高。绘制了适用于Ti6Al4V合金热冲压工艺的热加工图，表明应变速率对Ti6Al4V合金的热成形性有显著影响。在较高应变速率（>0.05s⁻¹）下，Ti6Al4V合金的热加工不易出现失稳现象。将热加工图与热冲压实验相结合，发现随着冲压速度的提高，零件的成形质量和厚度均匀性显著提高。利用扫描电子显微镜（SEM）、电子背散射衍射（EBSD）、X射线衍射（XRD）和透射电子显微镜（TEM）研究了不同加热温度条件下成形零件的相组成和微观组织，并确定热冲压成形的最高加热温度为875℃。基于对热冲压成形的盒形构件不同截面的EBSD测试，提出了Ti6Al4V合金热冲压中的再结晶机制。随着变形量的增加，动态再结晶（DRX）的作用增强。当变薄率达到15%时，DRX超过动态回复（DRV）成为主导软化机制。不同变薄率下的DRX晶粒通过不连续动态再结晶（DDRX）和连续动态再结晶（CDRX）形成，且CDRX始终是主导机制。
