Oxygen diffusion in Ti₃Al single crystals

Abstract

Diffusion coefficients of oxygen in directions parallel to the c- (D _c) and a-axis (D _a) of Ti₃Al single crystals were measured by oxygen implantation and Auger electron spectroscopy. The temperature dependence of D _c and D _a in the temperature range 723 − 1073 K is expressed as: and , respectively. The diffusion coefficients are three orders of magnitude less than those in α-Ti. The value of D _c/D _a is within the range 0.94 − 1.11 and the diffusion anisotropy is weak, despite the anisotropic arrangement of octahedral sites. The diffusion mechanism is discussed in terms of the ordered arrangement of two types of octahedral sites occupied by oxygen atoms.

Keywords:

• oxygen
• impurity diffusion
• interstitial
• intermetallic compound
• anisotropy
• titanium aluminide

Acknowledgements

The authors thank Professor H. Fujii and M. Kamai (Joining and Welding Research Institute, Osaka University, Japan) for their help with Auger electron spectroscopy, Dr. Nagamachi (Ion Engineering Center Corporation, Osaka, Japan) for ion implantation, Dr. T. Ikeda (Institute of Scientific and Industrial Research (ISIR), Osaka University; present address: California Institute of Technology) and Professor H. Nose (ISIR, Osaka University; present address: Kyoto University) for assistance in sample preparation. This work was supported by the ‘Priority Assistance of the Formation of Worldwide Renowned Centers of Research–The 21st Century COE Program (Project: Center of Excellence for Advanced Structural and Functional Materials Design)’ and partly by a Grant-in-Aid for Scientific Research Development from the Ministry of Education, Culture, Sports, Science and Technology of Japan.