Order–disorder transformation of the O phase in Ti₂AlNb alloys

Abstract

The free energy of the O₂ (Ti₂AlNb) phase, based on the Gorsky–Bragg–Williams (G–B–W) approximation considering nearest-neighbour interactions, has been utilized to derive expressions for the transition and instability temperatures. The relations among the long-range order parameter, transformation temperatures and free energy as a function of the concentrations of Al and Nb have been established. The results are compared with those of earlier experimental and theoretical investigations.

Acknowledgements

A.K.S. is grateful to the Ministry of Defence, Government of India, for providing financial support. We extend our thanks to Dr. D. Banerjee, Director Defence Metallurgical Research Laboratory, Hyderabad, India, for encouraging us to carry out this work.