Effect of forging on the microstructure and texture of a high Nb containing γ-TiAl alloy

• Published in: Journal of Central South University Vol. 31; no. 6; pp. 1763 - 1773
• Main Authors: Tao, Hui, Li, Hui-zhong, Wang, Li, Zhou, Rui, Che, Yi-xuan, Chen, Yong-hui, Liang, Xiao-peng
• Format: Journal Article
• Language: English
• Published: Changsha Central South University 01.06.2024; Springer Nature B.V
• Subjects: Beta phase; Casting alloys; Deformation; Dislocation density; Dynamic recrystallization; Electron microscopy; Engineering; Heat resistant alloys; Heat transmission; High temperature; Hot forging; Hot workability; Hot working; Intermetallic compounds; Kinking; Lamellar structure; Metallic Materials; Microscopy; Microstructure; Niobium; Solidification; Texture; Titanium aluminides; Titanium base alloys; Twin boundaries; phase; 高铌TiAl合金; 显微组织; 织构; microstructure; high Nb containing; texture; TiAl alloy; 锻造; forging; 相
• ISSN: 2095-2899; 2227-5223
• DOI: 10.1007/s11771-024-5677-5

The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W (at.%) alloy was investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the as-cast alloy is mainly composed of α 2 / γ lamellar colonies with a mean size of 70 µm, but the hot-forged pancake displays a near duplex microstructure (DP). Kinking and bending of lamellar colonies, deformation twinning and dynamic recrystallization (DRX) occur during hot forging. Meanwhile, dense dislocations in the β phase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy. Unlike the common TiAl casting texture, the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region, resulting in the formation of a γ fiber texture where the γ aligns parallel to the heat-flow direction. In comparison, the relatively strong and weak texture components in the as-forged alloy are attributed to the deformation twinning. After annealing, static recrystallization occurs at the twin boundary and intersections, which weakens the deformation texture.