Diffusion of chromium and manganese in γ-TiAl

Abstract

The γ-TiAl intermetallic compound with suitable alloying additions has shown considerable promise as a material for high-temperature applications. Diffusion studies in this alloy system are useful in assessment of their creep behaviour and structural stability in service conditions. Tracer diffusion coefficients of ⁵¹Cr and ⁵⁴Mn in a γ-TiAl intermetallic compound containing 54.1 at. % aluminium were determined in the temperature range from 1095 to 1470 K. The temperature dependence of both the diffusing species follows a linear Arrhenius behaviour and can be expressed as D _Cr = 4.4 × 10⁻³exp(−350 kJ mol⁻¹/RT) m²s⁻¹ and D _Mn = 1.2 × 10⁻³ ×exp(−326 kJ mol⁻¹/RT) m²s⁻¹. The data are analysed on the basis of empirical correlations between the diffusion and melting parameters applicable for conventional mono-vacancy diffusion mechanism in metals. It is concluded that impurity diffusion in γ-TiAl occurs through the migration of thermal vacancies via nearest-neighbour or next-nearest neighbour jumps.

Keywords:

• γ-TiAl alloy
• intermetallic
• diffusion
• chromium
• manganese
• vacancy mechanism

Acknowledgements

The authors are grateful to Dr R.S. Mehrotra for useful discussions and careful reading of the manuscript.