Diffusion of hydrogen in titanium, Ti88Al12 and Ti3Al

Abstract

Diffusion coefficients for hydrogen in titanium, its alloy Ti₈₈Al₁₂ and the intermetallic Ti₃Al have been measured in the temperature range 873–1298 K. It has been found that the activation energy for diffusion in Ti₃Al (0.84 eV) is nearly twice that in titanium (0.45 eV), and in Ti₈₈Al₁₂(0.57 eV) it is closer to that in titanium than that in Ti₃Al. The prefactor of the diffusion coefficient has been found to increase as the aluminium content increases. The activation energy and prefactor obtained for Ti₃Al are explained by the presence of ordered aluminium atoms in Ti₃Al as well as by the large difference in the heats of solution of hydrogen in titanium and aluminium. The diffusion coefficient of Ti₈₈Al₁₂ is modelled, assuming distributions of the prefactor and activation energy resulting from the disordered aluminium atoms.