Diffusion of aluminum in β-titanium

Abstract

Interdiffusion coefficient D in the β-phase of Ti-Al alloys has been determined by Matano's method in the temperature range 1323 to 1823 K with (pure Ti)-(Ti-8.5 at% Al alloy), (pure Ti)-(Ti-16.5 at% Al alloy) and (Ti-8.5 at% Al alloy)-(Ti-16.5 at% Al alloy) couples. In the whole temperature range the value of Ď increases gradually with increasing aluminum content. The Arrhenius plot of Ď up to 6 at% Al shows an upward curvature similar to that recognized in the self-diffusion in β-Ti. The curvature becomes small with increasing aluminum content, and it is nearly linear in the concentration more than 10 at% Al. The activation energies for the impurity diffusion in β-Ti are proportional to the square of radius of the diffusing atom. This suggests that the size effect is dominant in the impurity diffusion in β-Ti.