The Effects of Heat Treatments and Tungsten Additions on Microstructures and Tensile Properties of Powder Metallurgy Ti-48Al-2Nb-2Cr

Abstract:

The microstructures and tensile properties of a fully lamellar Ti-48Al-2Cr-2Nb, and two tungsten-modified versions, Ti-48Al-2Cr-2Nb-0.5W and Ti-48Al-2Cr-2Nb-1.0W (atomic percent) are investigated. Gas atomized powders are consolidated by hot isostatic pressing followed by solution treatment and aging. The microstructures are characterized by optical, scanning electron, and transmission electron microscopy and mechanical properties are characterized by room temperature tensile testing. The solution heat treatment, combined with controlled cooling, generates relatively fine, fully lamellar grains. Tungsten reduces the propensity for martensitic gamma formation during cooling, and slows down lamellar coarsening as well as the formation of equiaxed gamma phase during aging. The aging treatment stabilizes the microstructure and, in the tungsten-modified alloys, causes beta phase precipitation at lamellar interfaces and grain boundaries. Both aging and tungsten additions increase the alloy strength and reduce ductility. The fracture morphologies of the alloys are similar and exhibit mixed-mode fracture consisting of inter- and intra-granular cracking, as well as inter-lamellar cracking.

• Periodical: Materials Science Forum (Volumes 638-642)
• Pages: 1406-1411
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.638-642.1406
• Online since: January 2010
• Authors: Dongyi Seo, S. Bulmer, H. Saari, Peter Au
• Keywords: Aging, Beta Phase, Micro-Structure Evolution, Tensile Properties, TiAl, W

References

[1] Y-W. Kim, JOM. 46 (7), 1995, pp.39-41.

[2] Kim, Y-W., 1994, JOM, July, pp.30-39.

[3] W. Smarsly, H. Baur, et al, ISSI-3, 2001, pp.25-34.

[4] Lasalmonie, A., 2006, Intermetallics 14, pp.1123-1129.

[5] Weimer, M.J. and Kelly, T.J., 2006, 17 th AeroMat Conference & Exposition, May 15-18, 2006, Seattle, Washington.

[6] Huang, S-C., 1989, US Patent #4, 879, 092.

[7] Kim, Y-W. and Dimiduk, D. M, 1997, Structural Intermetallics 1997, M.V. Nathal et al., eds., TMS, Warrendale, PA, pp.531-543.

[8] J. Beddoes, W. Wallace, L. Zhao, Inter Mater Rev 1995; 40: 197.

[9] DY Seo, J. Beddoes, L. Zhao, Metall Mater Trans 2003; 34A: 2177.

[10] Scott Bulmer, M.A. Sc. Thesis, Carleton University, pp.49-73, (2008).

[11] DY Seo, J. Beddoes, L. Zhao, GA Botton, Mater Sci Eng 2002; A329-331: 810.

[12] H. Zhu, D. Y. Seo, K. Maruyama, and P. Au, Scripta Materialia, vol. 54, pp.425-430, (2006).

[13] U. Prasad and M. C. Chaturvedi, Metallurgical and Materials Transactions A, vol. 34A, pp.2053-2066, Oct. (2003).

[14] P. Wang and V. K. Vasudevan, Scripta Metallurgica et Materialia, vol. 27, pp.89-94, (1992).

[15] R. Kainuma, Y. Fujita, H. Mitsui, I. Ohnuma, and K. Ishida, Intermetallics, vol. 8, pp.855-867, (2000).

[16] D. J. Larson, C. T. Liu, and M. K. Miller, Materials Science and Engineering, vol. A239-240, pp.220-228, (1997).

[17] D. Y. Seo, S. Bulmer, H. Saari, P. Au, Materials Science Forum Vols. 561-565 (2007) pp.481-486.

DOI: 10.4028/www.scientific.net/msf.561-565.481

[18] R. Cao, M. X. Lei, J. H. Chen, and J. Zhang, Materials Science and Engineering A, vol. 465, pp.183-193, (2007).

[19] J. H. Chen, R. Cao, G. Z. Wang, and J. Zhang, Metallurgical and Materials Transactions A, vol. 35A, pp.439-457, (2004).