Xia Yu-Chi, Chen Xiao-Min, Lin Yong-Cheng, Lu Xian-Zheng
School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China.
College of Automotive and Mechanical Engineering, Changsha University of Science and Technology, Changsha 410114, China.
Materials (Basel). 2021 Dec 21;15(1):7. doi: 10.3390/ma15010007.
The hot deformation characteristics of a GH4169 superalloy are investigated at the temperature and strain rate ranges of 1193-1313 K and 0.01-1 s, respectively, through Gleeble-3500 simulator. The hot deformed microstructures are analyzed by optical microscopy (OM), transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD) technology. The effects of deformation parameters on the features of flow curves and annealing twins are discussed in detail. It is found that the shapes of flow curves are greatly affected by the deformation temperature. Broad peaks appear at low deformation temperatures or high strain rates. In addition, the evolution of annealing twins is significantly sensitive to the deformation degree, temperature, and strain rate. The fraction of annealing twins first decreases and then rises with the added deformation degree. This is because the initial annealing twin characters disappear at the relatively small strains, while the annealing twins rapidly generate with the growth of dynamic recrystallized grains during the subsequent hot deformation. The fraction of annealing twins is relatively high when the deformation temperature is high or the strain rate is low. In addition, the important role of annealing twins on dynamic recrystallization (DRX) behaviors are elucidated. The obvious bulging at initial twin boundaries, and the coherency of annealing twin boundaries with dynamic recrystallized grain boundaries, indicates that annealing twins can motivate the DRX nucleation during the hot deformation.
通过Gleeble-3500热模拟试验机，分别在1193 - 1313 K温度范围和0.01 - 1 s⁻¹应变速率范围内研究了GH4169高温合金的热变形特性。采用光学显微镜（OM）、透射电子显微镜（TEM）和电子背散射衍射（EBSD）技术对热变形后的微观组织进行了分析。详细讨论了变形参数对流变曲线特征和退火孪晶的影响。研究发现，流变曲线的形状受变形温度影响较大。在低变形温度或高应变速率下会出现宽峰。此外，退火孪晶的演变对流变程度、温度和应变速率非常敏感。随着流变程度的增加，退火孪晶的体积分数先减小后增大。这是因为初始退火孪晶特征在相对较小的应变下消失，而在随后的热变形过程中，随着动态再结晶晶粒的长大，退火孪晶迅速生成。当变形温度较高或应变速率较低时，退火孪晶的体积分数相对较高。此外，还阐明了退火孪晶在动态再结晶（DRX）行为中的重要作用。初始孪晶界处明显的鼓胀以及退火孪晶界与动态再结晶晶粒界的共格性，表明退火孪晶在热变形过程中能够促进DRX形核。
