Lv Shaomin, Jia Chonglin, He Xinbo, Wan Zhipeng, Li Xinxu, Qu Xuanhui
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China.
Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100094, China.
Materials (Basel). 2019 Nov 7;12(22):3667. doi: 10.3390/ma12223667.
The superplastic deformation of a hot-extruded GH4151 billet was investigated by means of tensile tests with the strain rates of 10 s, 5 × 10 s and 10 s and at temperatures at 1060 °C, 1080 °C and 1100 °C. The superplastic deformation of the GH4151 alloy was reported here for the first time. The results reveal that the uniform fine-grained GH4151 alloy exhibited an excellent superplasticity and high strain rate sensitivity (exceeded 0.5) under all experimental conditions. It was found that the increase of strain rate resulted in an increased average activation energy for superplastic deformation. A maximum elongation of 760.4% was determined at a temperature of 1080 °C and strain rate of 10 s. The average activation energy under different conditions suggested that the superplastic deformation with 1 × 10 s in this experiment is mainly deemed as the grain boundary sliding controlled by grain boundary diffusion. However, with a higher stain rate of 5 × 10 s and 1 × 10 s, the superplastic deformation is considered to be grain boundary sliding controlled by lattice diffusion. Based on the systematically microstructural examination using optical microscope (OM), SEM, electron backscatter diffraction (EBSD) and TEM techniques, the failure and dynamic recrystallization (DRX) nucleation mechanisms were proposed. The dominant nucleation mechanism of dynamic recrystallization (DRX) is the bulging of original grain boundaries, which is the typical feature of discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX) is merely an assistant mechanism of DRX. The main contributions of DRX on superplasticity elongation were derived from its grain refinement process.
通过在应变速率为10⁻⁴s⁻¹、5×10⁻⁴s⁻¹和10⁻³s⁻¹以及温度为1060℃、1080℃和1100℃的条件下进行拉伸试验，研究了热挤压GH4151坯料的超塑性变形。本文首次报道了GH4151合金的超塑性变形。结果表明，均匀细晶的GH4151合金在所有实验条件下均表现出优异的超塑性和高应变速率敏感性（超过0.5）。发现应变速率的增加导致超塑性变形的平均激活能增加。在1080℃温度和10⁻⁴s⁻¹应变速率下测定的最大伸长率为760.4%。不同条件下的平均激活能表明，本实验中1×10⁻⁴s⁻¹的超塑性变形主要被认为是由晶界扩散控制的晶界滑动。然而，在较高应变速率5×10⁻⁴s⁻¹和1×10⁻³s⁻¹时，超塑性变形被认为是由晶格扩散控制的晶界滑动。基于使用光学显微镜（OM）、扫描电子显微镜（SEM）、电子背散射衍射（EBSD）和透射电子显微镜（TEM）技术进行的系统微观结构检查，提出了失效和动态再结晶（DRX）形核机制。动态再结晶（DRX）的主导形核机制是原始晶界的鼓胀，这是不连续动态再结晶（DDRX）的典型特征，而连续动态再结晶（CDRX）仅仅是DRX的辅助机制。DRX对超塑性伸长的主要贡献源于其晶粒细化过程。
