Microstructures and Creep Behavior of As-Cast TiAl-Nb Alloy

Abstract:

By means of creep properties measurement and microstructure observation, an investigation was carried out to study the creep behaviors of the as-cast TiAl-Nb alloy at temperature near 910 oC. Results showed that the microstructure of as-cast TiAl-Nb alloy consisted of γ/α₂ phases with the lamellar feature, and the boundaries with irregular serrated configuration consisted of single γ phase, and located in between the lamellar γ/α₂ phases with different orientations. The as-cast TiAl-Nb alloy displayed a better creep resistance at high temperature and longer creep life. Compared to α₂ -Ti₃Al phase, the γ phase possessed a weaker strength, therefore, the crack was easily initiated along the boundaries at about 45° angles relative to the stress axis, and propagated along the boundaries parallel to the orientation of lamellar γ/α₂ phases up to the occurrence of creep fracture. Thereinto, the tearing edges formed on the surface of the fracture being inclined with the lamellar γ/α₂ phases are attributed to the α₂-Ti₃Al phase with better strength hindering the crack propagation during creep.

• Periodical: Materials Science Forum (Volume 816)
• Pages: 572-577
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.816.572
• Online since: April 2015
• Authors: Su Gui Tian*, Xiao Xia Wu, Hui Chen Yu, Hao Fang Sun, Ze Hui Jiao
• Keywords: Creep, Deformation Mechanism, Fracture Mechanism, Microstructure, TiAl-Nb Alloy

References

[1] J.P. Lin, X.J. Xu, Y.L. Wang, S.F. He, X.P. Song, G.L. Chen, High temperature deformation behaviors of a high Nb containing TiAl alloy, Intermetallics. 15 (2007) 668-674.

DOI: 10.1016/j.intermet.2006.10.029

[2] X. Lu, L.H. Zhao, L.P. Zhu, B. Zhang, X.H. Qu, High-temperature mechanical properties and deformation behavior of high Nb containing TiAl alloys fabricated by spark plasma sintering, Mater. 19 (2012) 354-359.

DOI: 10.1007/s12613-012-0563-9

[3] G.Q. Chen, B.G. Zhang, W. Liu, J.C. Feng, Crack formation and control upon the electron beam welding of TiAl-based alloys, Intermetallics. 19 (2011) 1857-1863.

DOI: 10.1016/j.intermet.2011.07.017

[4] Y.Q. Yan, L. Zhou, W.S. Wang, Y.N. Zhang, 8. 5 Nb–TiAl alloy with fine grains, Journal of alloys and compounds. 361 (2003) 241-261.

DOI: 10.1016/s0925-8388(03)00427-4

[5] Y.H. Wang, J.P. Lin, Y.H. He, Y.L. Wang, G.L. Chen, Diffusion behavior of Nb element in high NB containing TiAl alloys by reactive hot pressing, Rare Met. 25 (2006) 349-354.

DOI: 10.1016/s1001-0521(06)60066-1

[6] H.Y. Kim, K. Maruyama, Changes in lamellar microstructure by parallel twinning during creep in soft PST crystal of TiAl alloy, Trans. Nonferrous Met. Soc. China. 12 (2002) 561-568.

DOI: 10.1016/s1359-6454(01)00180-x

[7] S.G. Tian, Q. Wang, H.C. Yu, H.F. Sun, Q.Y. Li, Microstructure and creep behaviors of a high Nb-TiAl intermetallic compound based alloy, Mater. Trans. A. 614 (2014) 388-346.

DOI: 10.1016/j.msea.2014.06.117