Understanding the effect of tantalum on diffusion kinetics of the BCC β-(Ti, Al) phase following pseudo-binary diffusion couple method

Abstract

A study has been conducted to quantify the effect of Ta on diffusion kinetics of the β-(Ti, Al) solid solution body-centered cubic (BCC) phase by determining the interdiffusion and impurity diffusion coefficients using the novel pseudo-binary diffusion couple technique. The interdiffusion coefficients (D˜) for the ternary β-Ti(Al, Ta) system are higher than those of binary β-(Ti, Al) system for a particular annealing temperature and Al content. Increase in D˜ with addition of Ta has been attributed to a decrease in activation energy for interdiffusion for the Ta-containing β-phase as compared to the Ta-free β-phase owing to a reduction of activation energies for the formation of point defects and migration of the diffusing atoms. A higher impurity diffusion coefficient of Al for Ta-containing β-(Ti, Al) than Ta-free β further suggests an increase in the preferential interaction of vacancies with Al in the presence of Ta in the β-phase.