Composition dependence of atomic mobility in single phase γ TiAl intermetallic compounds

TiAl based intermetallic compounds are potential candidates for high temperature applications in aerospace systems and automobiles. An improved understanding of the high temperature characteristics of these materials requires a knowledge of atomic mobility and diffusion, and of their composition dependence. exp 44 Ti tracer diffusion data exist for gamma Ti sub 46 Al sub 54 , but there has been no investigation of composition effects. Tracer diffusion of Al has not been determined, due to the difficulties connected with the low specific activity and high cost of the exp 26 Al tracer. Some single phase interdiffusion results in TiAl have been obtained and seem to indicate that the Al diffusivity is about of the same order as the Ti diffusivity; no effect of Al concentration on the interdiffusion coefficient was apparent. Another possible approach to get information on the overall atomic mobility is to investigate atomic order changes induced by thermal treatments. The present investigation is a preliminary characterization, by such a method, of the atomic mobility as a function of composition in single phase gamma (L1 sub 0 ) TiAl, using high sensitivity residual electrical resistivity measurements.