Isothermal Deformation of Gamma Titanium Aluminide

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Gamma titanium aluminide has received considerable attention in recent years from the automotive industry as a potential material for making rotating and reciprocating components to produce a quieter and more efficient engine. This class of alloys was initially developed for the aerospace industry, though they have not yet been used in jet engines in a large scale. The dual advantages of lower density and higher maximum operating temperature than alloy steels makes these alloys candidates for rotating components in automobile engines. Gamma titanium aluminide base alloys generally are two phase (γ + α2) consisting of titanium and aluminum with one or more alloying elements added in small quantities. These alloying elements are added for specific property improvements; for example, 1-3% chromium for low temperature ductility improvements, 2% niobium for high temperature strength, and small amounts of boron for grain size control. For aerospace applications, these alloys generally undergo fairly complex processing, involving multiple extrusions, heat treatments, HIP’ing etc. The end product of such processing is a material which has excellent mechanical properties, but due to the complex processing route, also very expensive (1-6).

The objectives of this study were to identify processing routes for the manufacture of automobile valves from gamma titanium aluminide. The issues considered were microstructure and composition of the material, and! processing parameters such as deformation rates, temperatures, and total deformation. This paper examines isothermal deformation of gamma titanium aluminide in order to develop a processing window for this type of material.