Processing, microstructure and mechanical properties of pm gamma titanium aluminides

Gamma titanium aluminide alloys (TiAl) are receiving increasing attention as candidates for advanced structural materials in high temperature aerospace applications. Inert gas atomization of prealloyed powder followed by hot isostatic pressing (HIP) to full density is a viable approach for the production of forging and rolling performs as well as as-HIP components. The prealloyed powder metallurgy (PM) production route has the capability of producing a uniform and fine microstructure in preforms/components of any size. This paper will describe gamma titanium aluminide powder production, processing and characterization. Alloys such as Ti-48A1-2Nb-2Cr, Gamma Met (Ti-46.5Al-4(Nb,Ta,Cr,B), and 395MM (Ti-46Al-4(Nb,Mo,Cr, B,C) have been produced in quantities exceeding 500 kg. Microstructure and processing of consolidated material will be discussed. Thermally induced porosity (TIP) is a phenomenon, which occurs in any inert gas atomized powder. The results of a study to evaluate the effect of processing and heat treatment conditions on the microstructure and occurrence of TIP in gamma titanium aluminide powders will be presented. Mechanical properties of consolidated product will also be presented. (AU) © TMS (The Minerals, Metals & Materials Society), 2004