Kinetics of Ordering in Fe–Al Alloys

Abstract

The kinetics of ordering in Fe–Al alloys with about 25 at%Al is investigated both theoretically and experimentally. The kinetic equations which express the time variation of the degrees of order in B2 and DO3 structures are obtained by taking into account the direct interchange of atoms between the first and the second nearest neighbors. The experimental results of X-ray diffraction for these alloys on isothermal annealing or slow cooling are reproduced satisfactorily by theoretical rate equations, and the characteristics of the ordering in the Fe–Al system is investigated. The ordering in DO3 type is influenced substantially by the atomic interchange between the second nearest neighbors. The B2 type ordering takes place so rapidly that the quenching from a disordered phase does not prevent the ordering. An oscillatory change of the degree of order in the B2 structure is expected from the calculation in the isothermal annealing.