Guide
In this paper, the spheroidization behavior of the B2 phase in TiAl alloys under isothermal compression is revealed in detail. The results show that under the condition of 1 000 °C-80%-0.01 s-1, most of the B2 phases are bent and torsioned with the γ instead of spheroidization due to the insufficient deformation storage energy, and the decrease of temperature and the increase of strain energy further promote the spheroidization of B2 phase. The spheroidized B2 phase avoids the fragmentation of the traditional B2 relative to the TiAl matrix, which provides a new way to reduce the negative impact of the B2 phase in the TiAl alloy and develop advanced TiAl alloys.
After the addition of β stable elements, the B2 phase inevitably appears in the solidified structure of the TiAl alloy. The excessive precipitation of this ordered phase aggravates the stress concentration and reduces the plasticity of the TiAl alloy. Previous studies have shown that B2-free TiAl alloys can be obtained by reducing the content of β stable elements, but their hot workability is limited. The B2 phase is difficult to dissolve at low temperatures, while high temperatures are not conducive to obtaining fine sheets. Therefore, it remains challenging to retain the B2 phase while avoiding its adverse effects on the matrix.
Promoting the spheroidization transition of B2 phase is an ingenious method to reduce the fragmentation of sheet microstructures, thereby optimizing the thermal processability and mechanical properties of TiAl alloys, which requires the exploration of the formation mechanism of new microstructures. High-strain isothermal compression has been shown to be effective in improving microstructure.
近日，哈尔滨工业大学陈瑞润教授团队成功制备了超细晶粒微观结构和纳米球形B2相，并创新性地揭示了B2相在1 000 ℃-80%-0.01 s-1条件下的球化机理。 研究结果以题为“Synergistic effect of twin consumption within lamellae and slip system activation at grain boundary on the formation of nano-spherical B2 phase”发表于期刊《Scripta Materialia》。
The first author U21A2042 of the paper is Li Kexuan FRFCU5710051322 52101038, a doctoral student in the School of Materials Science and Engineering, Harbin Institute of Technology, and the corresponding authors are Associate Professor Fang Hongze and Professor Chen Ruirun.
Click on the image to read the original article
The results show that the HC-1 specimen exhibits a bent B2 phase and lamellar clusters with a small amount of recrystallized grains. The HC-2 specimen underwent a large grain refinement and B2 phase spheroidization transition. At 1 000 °C-80%-0.01 s-1, the B2 phase was nucleated and spheroidized in the γ phase layer by depleting the twin boundary. At the recrystallization grain boundaries of the γ phase, the B2 phase grows into a spherical crown under the combined action of favorable slip system activation, multiple dislocation shear, and coordinated deformation of the micro-slip zone.
