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.

Intermetallic β‐Solidifying γ‐TiAl Based Alloys − From Fundamental Research to Application

“…For these reasons, only special techniques as cruciblefree or cold crucible techniques can be employed. [224][225][226] With respect to other recent developments in the technology of TiAl alloys, for example, joining and oxidation protective coatings, the reader is referred to a vast amount of publications which can be easily accessed on the basis of a literary study, for example, by means of Scopus or equivalent search engines. For the subsequent powder handling, it is required that the powder can demounted and transferred into a system of glove boxes operated under Ar gas without breaking the inert gas line.…”