Novel design concepts for gamma-base titanium aluminide alloys

Two-phase titanium aluminide alloys are being considered as light-weight materials to replace nickel-base superalloys for some high temperature applications in energy conversion systems. Thus, their mechanical properties have to be assessed against the high standard set by the superalloys currently in use. In this respect most titanium aluminides are particularly inferior in high temperature strength and creep resistance even if these properties are related to density. In an attempt to overcome these problems several studies have been performed on titanium aluminides which have been subjected to solid solution and precipitation hardening. The intention of the present study is to examine more closely these strengthening processes in order to assess their potential for extending the service range of the titanium aluminides towards higher temperatures. There is growing evidence that two-phase titanium aluminides, microalloyed with carbon or niobium, can provide the necessary performance. Particular emphasis will be placed on processing routes acceptable for these materials.