Interdiffusion in the Ti-rich phases of the Ti-Al system

The interdiffusion coefficient (D) has been measured in the temperature range from 1442 to 1639 K as a function of the composition in the α (hexagonal close-packed, A3), α 2 (ordered hexagonal, D0 19 ), (body-centred cubic, A2) and γ (ordered face-centred cubic, L1 0 ) phases of the Ti-Al system. The concentration profiles were obtained by electron probe microanalysis, and the chemical diffusivity was extracted from the concentration profiles by the Boltzmann-Matano procedure. In all the phases the interdiffusion coefficients increase with increasing Al contents. This increase is large in the disordered phase α, but much smaller in the ordered phases α 2 and γ.