Equilibria on the Ordered Phase Fe₃Al

Abstract

Thermodynamic implication of the equilibrium phase diagram for order-disorder phase transitions in Fe₃Al alloy has been investigated by a statistical approach employing the Bragg-Williams approximation, in which the magnetic interactions are taken into account in the first and the second neighbor iron atoms as well as the usual atomic interactions up to the second neighbors. It is shown in the calculated diagram that the α+B2 phase is caused by the competition of both the atomic and magnetic interactions, with a ferromagnetic interaction between the first neighbor iron atoms and an antiferromagnetic interaction between the second neighbor iron atoms. It is also suggested from the configurational free energy curve that spinodal decomposition is expected within the α+B2 phase field in accordance with the result of our previous experimental observation.