Microstructural Investigation of Routes for Gamma Titanium Aluminides Production by Powder Metallurgy

Abstract:

The alloy design and efficient routes of TiAl processing are important technological challenges for the development of new aerospace systems. Gamma-TiAl alloys are potential replacements for nickel and conventional titanium alloys in hot sections of turbine engines, as well as in sub-structures of orbital platform vehicles. Powder metallurgy (P/M) of Ti-based alloys may lead to the obtainment of components having weak-to-absent textures, uniform grain structure and higher homogeneity compared with conventional wrought products. This paper aims to investigate the microstructural evolution and densification aspects involved in the obtainment of Ti-48Al-2Cr-2Nb (at.%) alloy by three P/M-processing routes. Samples were prepared from elemental and pre-alloyed powders mixed for 2 h, followed by cold uniaxial and isostatic pressing followed by sintering and hot pressing stages between 1100°C up to 1400°C, for 1 h. After metallographic preparation, sintered samples were characterized by means of scanning electron microscopy (SEM) in the backscattered mode (BSE), X-ray diffraction (XRD), and density measurements. The results showed the potential of TiAl pre-alloyed powders to prevent Kirkendall porosity. A full lamellar microstructure was obtained by the pressureless route while a duplex microstructure was observed in samples produced by the hot pressing route.

• Periodical: Key Engineering Materials (Volume 704)
• Pages: 204-213
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.704.204
• Online since: August 2016
• Authors: V.A.R. Henriques*, Eduardo T. Galvani, Carlos Alberto Alves Cairo, M.L.A. Graça, A.C.S.M. Dutra
• Keywords: Intermetallics, Microstructure, Powder metallurgy, Sintering, Titanium Aluminides

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