The Role of Interfacial Precipitates on Creep Behaviour of Power Metallurgy (PM) Ti-48Al-2Cr-2Nb+1W Alloy

Abstract:

Pre-alloyed powders with a nominal composition of Ti-48Al-2Cr-2Nb+1W were consolidated by hot isostatic pressing (HIP). After the HIP process, a step cooled heat treatment (SCHT) with a carefully controlled cooling rate was applied to homogenize the HIP’ed microstructure and produce a fully lamellar microstructure. Following the SCHT, various isothermal aging at 950 °C and step aging processes form interfacial precipitates at the lamellar interfaces. The morphology, size, and distribution of the precipitates are dependent on the aging condition. Creep tests were carried out in air at 760 °C and 276 MPa to investigate the effect of interfacial precipitates. Primary creep resistance and creep life of the 8 and 144 hr aged conditions are improved substantially compared to the unaged condition due to the existence of the interfacial precipitates. However, the step aging process improves the creep resistance only slightly, probably because of the size and distribution differences of the interfacial precipitates compared to the 144 hr aged condition. Microstructure control is important since it has a substantial influence on creep behavior, especially primary creep resistance.

• Periodical: Materials Science Forum (Volumes 654-656)
• Pages: 496-499
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.654-656.496
• Online since: June 2010
• Authors: Dongyi Seo, Scott Bulmer, H. Saari, Han Liang Zhu, Peter Au
• Keywords: Aging, Beta Phase, Creep, Interfacial Precipitate, TiAl Alloys

References

[1] P. Seidenman and D. Spanovich: Cutting Fuel Costs, on www. aviationweek. com (2005).

[2] Y-W. Kim in: Microstructure/Property Relationships in Titanium Aluminides and Alloys, ed. by Y-W. Kim and R.R. Boyer, TMS (1991), p.91.

[3] F. Appel and R. Wagner: Mater. Sci. and Eng. R22 (1998), p.187.

[4] D.Y. Seo, H. Saari, J. Beddoes, and L. Zhao, in: Structural Intermetallics, ed. by K.J. Hemker et al., TMS (2001), p.653.

[5] S. Bulmer, D.Y. Seo, H. Saari, P. Au, in: Aerospace Materials and Manufacturing: Emerging Materials, Processes and Repair Techniques, ed. by M. Jahazi et al., COM (2006), p.135.

[6] D. Y. Seo, S. Bulmer, H. Saari, P. Au: Mater. Sci. Forum Vol. 561-565 (2007) p.481.

[7] D. Y. Seo, J. Beddoes, L. Zhao, and G. A. Botton: Mater. Sci. Eng. A 329-331 (2002), p.810.

[8] D.Y. Seo, S. Bulmer, H. Saari, P. Au: Mater. Sci. Forum Vol. 638-642 (2010), p.1406.

[9] P. J. Maziasz, C. T. Liu, and J. L. Wright in: Structural Intermetallics, ed. by M.V. Nathal et al., TMS (1997), p.245.

[10] D. J. Larson, C. T. Liu, and M. K. Miller: Mater. Sci. Eng. A 239-240 (1997), p.220.