Powder Metallurgy and Heat Treatment Effects on Microstructure in a γ-TiAl Ti-4522XD Alloy

Abstract:

This investigation focuses on the microstructural refinement of the γ-TiAl intermetallic alloy Ti-45Al-2Nb-2Mn (at.%) + 0.8 (vol.%) TiB2 (Ti4522XD) processed by powder metallurgy. The alloy powders were manufactured using the Electrode Induction-melting Gas Atomization (EIGA) process and subsequently consolidated through Hot Isostatic Pressing (HIP), resulting in a near-γ microstructure.The study further explores the effects of three distinct thermal treatments on the microstruc ture: 1) heating to 1300°C for 2 hours followed by furnace cooling (HT1), 2) heating to 1300°C for 2 hours, then water quenching and aging at 850°C for 8 hours before furnace cooling (HT2), and 3) heating to 1300°C for 2 hours, followed by water quenching and aging at 700°C for 8 hours before furnace cooling (HT3). These processes were tailored to promote the development of duplex (DP) and fully lamellar (FL) microstructures. Characterization was performed using X-ray diffraction (XRD) to identify phase distributions and scanning electron microscopy (SEM) to examine the surface morphology. Transmission elec tron microscopy (TEM) was used for a preliminary assessment of actual lamellar spacing. As a result, two different microstructures were obtained: DP for HT1 and near fully lamellar (NFL) for HT2 and HT3, but differences in the final actual lamellar spacing were observed for these last two cases. Additionally, the presence of microcracks of different morphologies was observed by SEM prior to any mechanical testing.

• Periodical: Materials Science Forum (Volume 1146)
• Pages: 3-11
• DOI: https://doi.org/10.4028/p-gA8WDg
• Online since: March 2025
• Authors: Berta Ruiz-Palenzuela*, Ilchat Sabirov, Elisa Maria Ruiz-Navas
• Keywords: Intermetallics, Microstructure, Powder Metallurgy, Thermal Treatments, γ-TiAl

References

[1] D. G. Morris and M. A. Mun˜oz-Morris. Intermetallics: Past, present and future. Revista de Metalurgia (Madrid), SPEC. VOL.(c):498–501, 2005.

[2] K. Kothari, R. Radhakrishnan, and N. M. Wereley. Advances in gamma titanium aluminides and their manufacturing techniques. Progress in Aerospace Sciences, 55:1–16, 2012.

DOI: 10.1016/j.paerosci.2012.04.001

[3] A. Lasalmonie. Intermetallics: Why is it so difficult to introduce them in gas turbine engines? Intermetallics, 14(10-11):1123–1129, 2006.

DOI: 10.1016/j.intermet.2006.01.064

[4] F. Appel, J. D. H. Paul, and M. Oehring. Gamma Titanium Aluminide Alloys: Science and Technology. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2011.

DOI: 10.1002/9783527636204

[5] H. Clemens and H. Kestler. Processing and applications of intermetallic γ-TiAl-based alloys. Advanced Engineering Materials, 2(9):551–570, 2000.

DOI: 10.1002/1527-2648(200009)2:9<551::aid-adem551>3.3.co;2-l

[6] R. M. Moreno. In situ analysis of the high temperature deformation and fracture mechanisms. PhD thesis, University Carlos III of Madrid, May 2014.

[7] B. P. Bewlay, S. Nag, A. Suzuki, and M. J. Weimer. TiAl alloys in commercial aircraft engines. Materials at High Temperatures, 33(4-5):549–559, 2016.

DOI: 10.1080/09603409.2016.1183068

[8] H. Clemens and S. Mayer. Intermetallic titanium aluminides in aerospace applications – processing, microstructure and properties. Materials at High Temperatures, 33(4-5):560–570, 2016.

DOI: 10.1080/09603409.2016.1163792

[9] B. Liu and Y. Liu. Powder metallurgy titanium aluminide alloys. Elsevier Inc., 2015.

[10] C. Leyens and M. Peters. Titanium and titanium alloys: Fundamentals and applications. Wiley- VCH, 2003.

[11] U. Habel and B. J. McTernan. HIP temperature and properties of a gas-atomized γ-titanium aluminide alloy. Intermetallics, 12(1):63–68, 2004.

DOI: 10.1016/j.intermet.2003.08.006

[12] G. Cao, L. Fu, J. Lin, Y. Zhang, and C. Chen. The relationships of microstructure and properties of a fully lamellar TiAl alloy. Intermetallics, 8(5-6):647–653, 2000.

DOI: 10.1016/s0966-9795(99)00128-4

[13] R. T. Zheng, G. A. Cheng, G. X. Cao X. J. Li, Y. G. Zhang L. F. Fu, and C. Q. Chen. The relationship between fracture toughness and microstructure of fully lamellar TiAl alloy. Journal of Materials Science, 42(4):1251–1260, 2007.

DOI: 10.1007/s10853-006-1382-z

[14] R. Gerling, H. Clemens, and F. P. Schimansky. Powder metallurgical processing of intermetallic gamma titanium aluminides. Advanced Engineering Materials, 6(1-2):23–38, 2004.

DOI: 10.1002/adem.200310559

[15] D. Y. Seo, L. Zhao, and J. Beddoes. Microstructural evolution during heat treatments in Ti-45 and 47Al-2Nb-2Mn + 0.8 vol% TiB2 XDTM alloys. Materials Science and Engineering A, 329-331:130–140, 2002.

DOI: 10.1016/s0921-5093(01)01546-5

[16] M. Su, Z. Lang, L. Zheng, J. Yan, K. Guan, and H. Zhang. Effect of heat treatment on microstructures and mechanical properties in a full lamellar TiAl alloy. Materials Science and Engineering A, 15(3):455–460, 2012.

DOI: 10.1590/s1516-14392012005000059

[17] T. Novoselova, S. Malinov, and W. Sha. Experimental study of the effects of heat treatment on microstructure and grain size of a gamma TiAl alloy. Intermetallics, 11(5):491–499, 2003.

DOI: 10.1016/s0966-9795(03)00028-1

[18] G. Wegmann, R. Gerling, and F. Peter Schimansky. Temperature induced porosity in hot isostatically pressed gamma titanium aluminide alloy powders. Acta Materialia, 51(3): 741–752, 2003.

DOI: 10.1016/s1359-6454(02)00465-2

[19] Z. Zhang, Q. Sun, C. Li, and W. Zhao. Theoretical calculation of the strain-hardening exponent and strength coefficient of intermetallic gamma titanium aluminide alloys. Journal of Materials Engineering and Performance, 15(1):22–26, 2006.

DOI: 10.1361/10599490524057

[20] K. Young-Won. Intermetallic alloys based on gamma titanium aluminide. JOM, 41(7): 24–30, 1989.

DOI: 10.1007/bf03220267