Response of the solidification microstructure of a high Nb containing TiAl alloy to an isothermal high-temperature heat treatment

• Published in: Intermetallics 2015-08, Vol.63, p.1-6
• Main Authors: Yang, Guang, Kou, Hongchao, Liu, Yi, Yang, Jieren, Wang, Jun, Zhang, Shouyin, Li, Jinshan, Fu, Hengzhi
• Format: Article
• Language: English
• Subjects: A. Intermetallics; C. Casting; D. Microstructure; D. Segregation; F. Electron microprobe; Heat treatment; Intermetallic compounds; Intermetallics; Microstructure; Niobium base alloys; Solidification; Titanium aluminides; Titanium base alloys; Titanium compounds
• ISSN: 0966-9795
• DOI: 10.1016/j.intermet.2015.03.015

Vacuum induction melting device combined with temperature control system was employed to investigate the effect of isothermal heat treatment (IHT) during solidification process on the microstructure evolution of a high Nb containing TiAl alloy. The microstructures of the alloy in as-cast condition and after IHT were studied. The results show that the as-cast microstructures exhibit a significant microstructural inhomogeneity with fine grains in dendrite core and coarse grains in interdendritic region. A new treatment approach by means of a short-term IHT within the β phase field during solidification process is proposed to obtain a uniform and refined microstructure. Compared with the as-cast alloy, IHT can reduce the tendency for crack. This phenomenon is attributed to the improvement of microstructural homogeneity by the elimination of peritectic α phase and the microstructure refinement by β → α transformation. •A new method is proposed to control the microstructure of Nb-rich TiAl alloys.•Isothermal heat treatment can produce uniform and refined microstructures.•Isothermal heat treatment can reduce the tendency for crack.